Cyanobacteria: Metabolisms to Molecules

Cyanobacteria, the ancient photoautotrophs on the Earth have always been regarded as the most important organism to sustain life in the planet. They are among the first pioneering communities on various harsh habitat, hydrarch or xerarch, which finally facilitate the emergence of vast communities including higher plants. Being the progenitor of chloroplast, the cyanobacterial metabolisms has always fascinated microbiologist. Additionally, the ability of these prokaryotes to produce valuable and prolific sources of natural products signified their role in array of industrial sectors. Further, the attempts to engineer the cyanobacterial metabolisms in way to enhance production of these metabolites are gradually increasing. Therefore, in this book, we proposed to accumulate the knowledge of cyanobacterial metabolisms and molecules as an asset for students, researchers, and biotechnologists. Cyanobacteria: Metabolisms to Molecules will cover diversity, fundamental metabolisms, crucial metabolities and their synthesis, and bioinformatics.

• Casts light on cyanobacterial assistance and their potential role in sustainable developments
• Provides significant insights into the fundamentals of cyanobacterial metabolism as well as lesser known topics
• Determines the role of cyanobacteria in public health

• Language: English
• Publisher: Academic Press
• Release date: Nov 24, 2023
• ISBN: 9780443132322

Book preview

Front Cover for Cyanobacteria - Metabolisms to Molecules - 1st edition - by Arun Kumar Mishra, Satya Shila Singh

Cyanobacteria

Metabolisms to Molecules

Edited by

Arun Kumar Mishra

Laboratory of Microbial Genetics, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Satya Shila Singh

Laboratory of Cyanobacterial Systematics and Stress Biology, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Table of Contents

Cover image

Title page

Copyright

Dedication

List of contributors

Preface

Chapter 1. Cyanobacteria—the pioneering photoautotrophs

Abstract

1.1 Introduction

1.2 Atmosphere on primitive Earth

1.3 Archean life

1.4 The first phototrophs: bacteria versus cyanobacteria

1.5 Modern phototrophic genera

1.6 The transition from an anoxygenic to an oxygenic environment

1.7 Early evolution of cyanobacteria

1.8 Photosynthetic apparatus

1.9 Photosystems I and II

1.10 Higher plant chloroplast inheritance via endosymbiosis

1.11 Conclusion

Acknowledgment

Competing interests

References

Chapter 2. Circadian cycle of cyanobacteria: mechanistic prospect and evolution

Abstract

2.1 Introduction

2.2 Fundamental components of the circadian clock: structure and function

2.3 Molecular mechanism of cyanobacterial clockwork

2.4 Diversity in KaiC-based timing systems of cyanobacteria

2.5 Evolution of the circadian clock system in the cyanobacteria

2.6 Conclusion and future perspectives

Acknowledgments

Conflict of interest

References

Chapter 3. Carbon concentrating mechanism in cyanobacteria: necessity and evolution

Abstract

3.1 Introduction

3.2 The basic structure of cyanobacterial CO2 concentrating mechanism

3.3 Evolution of CO2 concentrating mechanism and its necessity

3.4 Conclusion

Acknowledgments

Conflict of interest

References

Chapter 4. Cyanobacterial respiration

Abstract

4.1 Introduction

4.2 Components of cyanobacterial respiratory electron transport chain

4.3 Genes regulating cyanobacterial respiration

4.4 Significance of cyanobacterial respiration

4.5 Conclusion

Acknowledgments

Declaration of competing interest

References

Chapter 5. Lipid metabolism in cyanobacteria: biosynthesis and utilization

Abstract

5.1 Biosynthesis of lipids

5.2 Free fatty acid secretion and recycling

5.3 Storage of lipids and lipid-related products: alka(e)ne, poly-β-hydroxybutyrate and modifications of their biosynthesis

Acknowledgments

Conflict of interest

References

Chapter 6. Sulfur metabolism in cyanobacteria

Abstract

6.1 Introduction

6.2 Assimilatory sulfate reduction in cyanobacteria

6.3 Methionine biosynthesis

6.4 Hydrogen sulfide metabolism

6.5 Sulfolipids

6.6 Cyanobacterial secondary sulfur metabolism

6.7 Sulfur starvation

6.8 Sulfur compounds in stress response

6.9 Open questions

Acknowledgment

Conflict of interest

References

Chapter 7. Phosphate metabolism in cyanobacteria: fundamental prospective and applications

Abstract

7.1 Introduction

7.2 Phosphate uptake in cyanobacteria

7.3 Polyphosphates as a multifunctional phosphate reservoir in cyanobacteria

7.4 Phosphate limitation and its regulation

7.5 Application

7.6 Conclusion and future perspective

Acknowledgments

Conflict of interest

References

Chapter 8. Redox cycle: signaling and metabolic cross-talks in cyanobacteria

Abstract

8.1 Introduction

8.2 Major redox couples in the cyanobacteria and their role in signaling and metabolic cross-talks

8.3 Antioxidative enzymes: types, mode of action, and role in the redox cycle of cyanobacteria

8.4 Nonenzymatic antioxidants: effect on redox cycle and metabolism of cyanobacteria

8.5 Conclusions

8.6 Future perspective

Acknowledgments

Conflict of interest

References

Chapter 9. Glutathione metabolism and regulation in cyanobacteria

Abstract

9.1 Introduction

9.2 Glutathione—a nonenzymatic antioxidant

9.3 Glutathione as a major player in the antioxidative system of cyanobacteria

9.4 Glutathione synthesis

9.5 Subcellular localization of glutathione

9.6 Degradation of glutathione

9.7 Glutathione metabolism

9.8 Effect of light and glucose on glutathione metabolism

9.9 Recent developments in glutathione detection

9.10 Roles of glutathione in diverse bacteria

9.11 Conclusion

Acknowledgments

Conflict of interest

References

Chapter 10. Nitric oxide synthases in cyanobacteria: an overview on their occurrence, structure, and function

Abstract

Abbreviations

10.1 Introduction

10.2 Nitric oxide synthases: structure and catalysis

10.3 Phylogenetic occurrence and diversity of cyanobacterial nitric oxide synthases

10.4 Redox and ionic interaction requirements of nitric oxide synthases from cyanobacteria

10.5 Synechococcus PCC 7335 and Aphanizomenon flos-aquae: case studies of nitric oxide synthase activity and function in cyanobacteria

10.6 There are other ways to produce nitric oxide: generation by nitrite reduction

10.7 Chemistry of nitric oxide in biological systems

10.8 Function of nitric oxide as a molecular messenger in cyanobacteria

10.9 Conclusions and future research directions

Acknowledgments

Conflict of interest

References

Chapter 11. Cyanophages: interacting mechanism and evolutionary significance

Abstract

11.1 Introduction

11.2 Diversity and specificity

11.3 Cyanophage–cyanobacterial interaction

11.4 Exploring the ecological significance of cyanophages: the hidden heroes of marine ecosystems

11.5 Conclusion and future perspective

Acknowledgments

Conflict of interest

References

Chapter 12. Secondary metabolites in cyanobacteria

Abstract

12.1 Notion of secondary metabolites

12.2 Secondary metabolites in cyanobacteria

12.3 Conclusion and future perspective

Acknowledgment

Conflict of interest

References

Chapter 13. The hidden world of cyanobacterial cell death: classification, regulatory mechanisms, and ecological significance

Abstract

13.1 Introduction

13.2 Types, subtypes, and routines of cell death in cyanobacteria

13.3 How to study cell death in cyanobacteria?

13.4 Caspase-homologs in cyanobacteria

13.5 Regulated cell death enhances cyanobacterial fitness

13.6 Ecological significance of cyanobacterial cell death

13.7 Conclusions and future prospective

Acknowledgments

Conflict of interest

References

Chapter 14. Cyanobacteria: a precious bioresource for bioremediation

Abstract

14.1 Introduction

14.2 Strategies for bioremediation

14.3 Cyanobacteria in sustainable environment management

14.4 Different mechanisms of bioremediation followed by cyanobacteria

14.5 Cyanoremediation of polluted ecosystems

14.6 Bioremediation of wastewater by cyanobacteria

14.7 Genetic engineering in cyanoremediation

14.8 Benefits of cyanoremediation

14.9 Conclusion and future perspectives

Acknowledgments

Conflict of interest

References

Chapter 15. Stress biology and signal perceptions in cyanobacteria

Abstract

15.1 Introduction

15.2 Global understanding of light stress

15.3 Cold stress response

15.4 Heat shock response and mechanism of adaptation

15.5 Nutrient starvation alters cyanobacterial physiology

15.6 Metal toxicity

15.7 Salinity stress response and tolerance

15.8 Stress responsive proteomic alterations in cyanobacteria

15.9 Conclusion

Acknowledgments

Conflict of interest

References

Chapter 16. Cyanobacterial interactions and symbiosis

Abstract

16.1 Introduction

16.2 Cyanobacterial existence and symbiosis

16.3 Cyanobacterial interaction with unicellular eukaryotes (protists)

16.4 Lichens: fungi-cyanobacteria symbiosis

16.5 Cyanobacterial interaction in marine organisms

16.6 Plant-cyanobacterial symbiosis

16.7 Cyanobacteria-bryophyte symbioses

16.8 Cyanobacterial symbionts from angiosperm

16.9 Ecological interactions of cyanobacteria

16.10 Applications of cyanobacterial association

16.11 Conclusions

Author contributions

Acknowledgments

Conflict of interest

References

Chapter 17. Metabolic engineering of cyanobacteria for biotechnological applications

Abstract

17.1 Introduction

17.2 Cyanobacterial metabolites and their applications

17.3 Metabolic engineering of cyanobacteria: tools and techniques

17.4 Genome-scale modeling and flux balance analyses

17.5 Genome editing

17.6 Future prospects

Acknowledgment

Conflict of interest

References

Chapter 18. Bioinformatics in delineating cyanobacterial metabolisms

Abstract

18.1 Introduction

18.2 Genomics in cyanobacterial metabolism

18.3 Proteomics in cyanobacterial metabolism

18.4 Transcriptomics in cyanobacterial metabolism

18.5 Metabolomics in cyanobacterial metabolism

18.6 Conclusions and future prospects

Acknowledgment

Competing interests

References

Chapter 19. Cyanobacterial lectins: potential emerging therapeutics

Abstract

19.1 Introduction

19.2 Structural features and glycan specificity of cyanobacterial lectins

19.3 Hemagglutination properties of cyanobacterial lectins

19.4 Antimicrobial and anticancer activities of cyanobacterial lectins

19.5 Computational biology-based study of uncharacterized lectins of cyanobacteria

19.6 Conclusions

19.7 Future perspectives

Acknowledgments

Conflict of interest

References

Chapter 20. Cyanobacteria: a key player in nutrient cycling

Abstract

20.1 Introduction

20.2 Cyanobacteria and nitrogen cycling

20.3 Cyanobacteria and carbon cycling

20.4 Cyanobacteria and phosphorus cycling

20.5 Cyanobacteria and sulfur cycling

20.6 Cyanobacterial blooms and their impact on nutrient cycling

20.7 Applications of cyanobacteria in nutrient cycling

20.8 Conclusion

Acknowledgments

Conflict of interest

References

Index

Copyright

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Dedication

This book is dedicated to our beloved teacher Prof. Devendra Nath Tiwari.

Prof. Devendra Nath Tiwari, our revered teacher and internationally recognized and highly admired cyanobacteriologist, has served as the head and coordinator of Centre of Advance Studies in Botany, Banaras Hindu University and superannuated as a professor in June 2006. He has been accredited for pioneering ideas and research works in the field of cyanobacterial genetics, heterocyte development, and nitrogen fixation. He and his group have published several original research articles in national and international journals of high repute. Nevertheless, the ultraviolet-induced morphological mutation of Nostoc linckia from uniseriate filaments to branched form is one of the landmark findings of his time, which was subsequently published in Nature in 1969. Being a brilliant student, Prof. Tiwari secured first division with distinction in his bachelor degree in the year 1963 from prestigious Calcutta University. His dedication and continuous hard work paid off as he got first class degree and gold medal in M.Sc. in the year 1966 from Banaras Hindu University. He was a recipient of UGC and CSIR fellowships during his PhD under the supervision of highly esteemed and globally renowned phycologist Prof. Ram Nagina Singh. Prof. Tiwari has also served in the Durham University, England as a visiting faculty from 1985 to 1986, Michigan State University, United States (1991), and Mu’tah University, Jordan (1993). He has worked with internationally recognized esteemed cyanobacteriologists like Prof. C. Peter Wolk and Prof. Brian A. Whitton on heterocyte development, nitrogen fixation, and nutrient dynamics. Prof. Tiwari also served as the dean at School of Life Sciences, Mizoram Central University (2006–09). His contributions and efforts to endorse the field of cyanobacterial research not only in Banaras Hindu University but also in several other prestigious life science institutes across India are inimitable. We and other being his students always look up to him with affection and gratitude not only as a great researcher but also as an outstanding teacher.

List of contributors

Anabella Aguilera,     Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden

Kannikka Behl,     Centre for Conservation and Utilisation of Blue Green Algae, Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, India

Alka Bhardwaj,     Laboratory of Microbial Genetics, Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Samujjal Bhattacharjee,     Laboratory of Microbial Genetics, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Liliana Cepoi,     Institute of Microbiology and Biotechnology, Technical University of Moldova, Chişinu, Moldova

Hillol Chakdar,     Microbial Technology Unit II, ICAR-National Bureau of Agriculturally Important Microorganisms (NBAIM), Kushmaur, Mau, Uttar Pradesh, India

Sindhunath Chakraborty,     Laboratory of Microbial Genetics, Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Prassan Choudhary,     Microbial Technology Unit II, ICAR-National Bureau of Agriculturally Important Microorganisms (NBAIM), Kushmaur, Mau, Uttar Pradesh, India

Natalia Correa-Aragunde,     Instituto de Investigaciones Biológicas-CONICET, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina

Pawan K. Dadheech,     Department of Microbiology, Central University of Rajasthan, Bandarsinndri, Rajasthan, India

Fiorella Del Castello,     Instituto de Investigaciones Biológicas-CONICET, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina

Manoharan Devaprakash,     Department of Molecular Microbiology, School of Biotechnology, Madurai Kamaraj University, Madurai, Tamil Nadu, India

Alka Devi,     Centre for Conservation and Utilisation of Blue Green Algae, Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, India

Kamonchanock Eungrasamee,     Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand

María Belén Fernández,     Instituto de Investigaciones Biológicas-CONICET, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina

Noelia Foresi,     Instituto de Investigaciones Biológicas-CONICET, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina

Anjali Gupta,     Centre of Advanced Study in Botany, Department of Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Neha Gupta,     Laboratory of Microbial Genetics, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Rinkesh Gupta,     Centre of Advanced Study in Botany, Department of Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Pranita Jaiswal,     Centre for Conservation and Utilisation of Blue Green Algae, Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, India

Tameshwar Prasad Jaiswal,     Laboratory of Cyanobacterial Systematics and Stress Biology, Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Saowarath Jantaro,     Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand

Parisa Rahimzadeh Karvansara,     Laboratory of Photosynthesis, Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czech Republic

Shreya Kesarwani,     Laboratory of Cyanobacterial Systematics and Stress Biology, Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Josef Komenda,     Laboratory of Photosynthesis, Centre Algatech, Institute of Microbiology of the Czech Academy of Sciences, Třeboň, Czech Republic

Stanislav Kopriva,     Institute for Plant Sciences, Cluster of Excellence on Plant Sciences, University of Cologne, Cologne, Germany

Ravinsh Kumar,     Department of Life Science, School of Earth, Biological and Environmental Sciences, Central University of South Bihar, Gaya, Bihar, India

Peter Lindblad,     Microbial Chemistry, Department of Chemistry-Ångström Laboratory, Uppsala University, Uppsala, Sweden

Xufeng Liu,     Microbial Chemistry, Department of Chemistry-Ångström Laboratory, Uppsala University, Uppsala, Sweden

Lovely Mahawar,     Institute of Plant and Environmental Sciences, Faculty of Agrobiology and Food Resources, Slovak University of Agriculture, Nitra, Slovakia

María Victoria Martin,     Instituto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC-CONICET), Fundación para Investigaciones Biológicas Aplicadas (CIB-FIBA), Universidad Nacional de Mar del Plata, Mar del Plata, Argentina

Aditi Mishra,     Laboratory of Cyanobacterial Systematics and Stress Biology, Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Arun Kumar Mishra,     Laboratory of Microbial Genetics, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Soumila Mondal,     Centre of Advanced Study in Botany, Department of Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Andrés Nejamkin,     Instituto de Investigaciones Biológicas-CONICET, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina

Aparna Pandey,     Ranjan Plant Physiology and Biochemistry Laboratory, Department of Botany, University of Allahabad, Prayagraj, Uttar Pradesh, India

Priyul Pandey,     Centre of Advanced Study in Botany, Department of Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Sakshi Pandey,     Ranjan Plant Physiology and Biochemistry Laboratory, Department of Botany, University of Allahabad, Prayagraj, Uttar Pradesh, India

Anirbana Parida,     Laboratory of Microbial Genetics, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Sheo Mohan Prasad,     Ranjan Plant Physiology and Biochemistry Laboratory, Department of Botany, University of Allahabad, Prayagraj, Uttar Pradesh, India

Priyanka,     Laboratory of Cyanobacterial Systematics and Stress Biology, Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Sanjay Sharma,     Laboratory of Cyanobacterial Systematics and Stress Biology, Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Rajaram Shyamkumar,     Department of Biotechnology, Kamaraj College of Engineering and Technology, Virudhunagar, Tamil Nadu, India

Ashutosh Singh,     Department of Life Science, School of Earth, Biological and Environmental Sciences, Central University of South Bihar, Gaya, Bihar, India

Prashansa Singh,     Laboratory of Microbial Genetics, Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Pratika Singh,     Department of Life Science, School of Earth, Biological and Environmental Sciences, Central University of South Bihar, Gaya, Bihar, India

Satya Shila Singh,     Laboratory of Cyanobacterial Systematics and Stress Biology, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Shailendra P. Singh,     Centre of Advanced Study in Botany, Department of Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Rajeshwar P. Sinha,     Laboratory of Photobiology and Molecular Microbiology, Centre of Advanced Study in Botany, Institute of Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Natesan Sivakumar,     Department of Molecular Microbiology, School of Biotechnology, Madurai Kamaraj University, Madurai, Tamil Nadu, India

Sonam,     Department of Microbiology, Central University of Rajasthan, Bandarsinndri, Rajasthan, India

Amrita Srivastava,     Department of Life Science, School of Earth, Biological and Environmental Sciences, Central University of South Bihar, Gaya, Bihar, India

Ankit Srivastava,     Laboratory of Microbial Genetics, Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Shobit Thapa,     Microbial Technology Unit II, ICAR-National Bureau of Agriculturally Important Microorganisms (NBAIM), Kushmaur, Mau, Uttar Pradesh, India

Ramachandran Thirumalaivasan,     Department of Molecular Microbiology, School of Biotechnology, Madurai Kamaraj University, Madurai, Tamil Nadu, India

Balkrishna Tiwari,     Genetics and Tree Improvement Division, ICFRE-Himalayan Forest Research Institute, Conifer Campus, Panthaghati, Shimla, Himachal Pradesh, India

Ranjan Kumar Tiwari,     Laboratory of Cyanobacterial Systematics and Stress Biology, Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Sapna Tiwari,     Centre of Advanced Study in Botany, Department of Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Nidhi Verma,     B K Birla Institute of Higher Education, Pilani, Rajasthan, India

Shaloo Verma,     Microbial Technology Unit II, ICAR-National Bureau of Agriculturally Important Microorganisms (NBAIM), Kushmaur, Mau, Uttar Pradesh, India

Ritu Vishwakarma,     Microbial Technology Unit II, ICAR-National Bureau of Agriculturally Important Microorganisms (NBAIM), Kushmaur, Mau, Uttar Pradesh, India

Yamini Yadav,     Centre for Conservation and Utilisation of Blue Green Algae, Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi, India

Zhi Zhu

The Key Laboratory of Biotechnology for Medicinal Plants of Jiangsu Province, School of Life Sciences, Jiangsu Normal University, Xuzhou, P.R. China

Microbial Chemistry, Department of Chemistry-Ångström Laboratory, Uppsala University, Uppsala, Sweden

Preface

Arun Kumar Mishra and Satya Shila Singh

Cyanobacteria are one of the ancient and crucial life forms on the Earth as they have not only inhabited the planet for more than 3.5 billion years ago but also played a pivotal role in Great Oxidation Event which has transformed the Earth’s atmosphere. Apart from being the progenitor of plant’s chloroplast, this group of photoautotrophic prokaryotes resembles physiological, and sometimes morphological, similarities to eukaryotic algae, thus they are also known as blue-green algae. The diverse and elaborate morphology of cyanobacteria, which range from single cell to multiaxial branched thallus, is unique and phenomenal. Moreover, several subgroups of cyanobacteria depict cell differentiation for specialized functions such as heterocyte formation in Nostocales for nitrogen fixation, akinetes, germinating spores, and the formation of hormogonia, the fundamental unit of infection. Besides, the robust physiological capabilities include nitrogen fixation and comprehensive antioxidative system that enhances the ability to thrive in arrays of ecosystems. The cosmopolitan distribution and paramount diversity across various environmental conditions from arctic to thermal hot springs, free-living to symbiotic associations, is the testimony to their plasticity and resilience, conferring their physiological potency. The ability of cyanobacteria to synchronize the operation of fundamental and bioenergetic processes in incipient cell types suggests pinpointed regulation of metabolisms. The photosynthetic and diazotrophic nature of cyanobacteria confer them as crucial component of biogeochemical cycles. Because of being a unique group of prokaryote having several advantages, cyanobacteria are largely used in various biotechnological and industrial applications such as biofuel production, biofertilizers, pharmaceuticals, cosmetics, and nutraceuticals. recent studies also exhibited bioremediating capabilities of cyanobacteria for variety of toxicants and emerging contaminants. However, the utilization of cyanobacteria in reclamation of usar lands were well studied and documented long ago. The ever-rising research interests in this group of organisms and comprehensive utilization of their potential in commercial aspects compels young scientists to know more about cyanobacteria.

In consideration to this, we have compiled comprehensive knowledge about cyanobacteria in this book entitled Cyanobacteria: Metabolisms to Molecules. This book explores different aspects related to cyanobacteria comprising interesting facts and perceptions revolving around the photoautotrophs. The book subsumes 20 chapters covering topics related to origin and history of cyanobacteria, fundamental physiological processes, biotic and abiotic interactions, molecular regulation, and bioprospection. Besides, a significant portion of the book provides critical insights on the juvenile topics such as nitric oxide synthase regulation and homeostasis, cyanophage interactions, regulated cell demise, and therapeutic potential of cyanobacteria. Descriptive account on the metabolic engineering–based industrial application and databases for cyanobacterial-omics have also been catalogued. All these topics are comprehensively designed for better understanding by nationally and internationally recognized authors having illustrious career in the field of cyanobacterial research and teaching.

We intend to promote in-depth studies in cyanobacterial metabolisms and bioprospection where this book can be instrumental. Hope that the book will provide valuable knowledge not only to the research community and scholars but also to undergraduate and postgraduate students. This book may serve as a crucial reference for teaching institutes for designing up-to-date and comprehensive syllabi for cyanobacteria.

We confer our indebtedness to all the contributors for valuable operation in completing the book on time. We sincerely thank Prof. D. N. Tiwari (Department of Botany, Banaras Hindu University) for his insightful guidance and suggestions. We acknowledge the support of Head, Department of Botany, Banaras Hindu University for providing necessary facilities and owe our gratitude and affection to our families for their blessings.

Chapter 1

Cyanobacteria—the pioneering photoautotrophs

Sonam and Pawan K. Dadheech,    Department of Microbiology, Central University of Rajasthan, Bandarsinndri, Rajasthan, India

Abstract

Every living being needs a supply of energy to carry out fundamental processes. Photoautotrophy emerged as an efficient mode of nutrition than other forms. The harsh environment on the primitive Earth restricted the availability of essential substances required to produce organic matter, therefore selective pressure such as paucity of electron suppliers and UV light selection pressures led to the emergence of photoautotrophic microorganisms that could harness the sun’s energy to power through metabolic processes. The primary atmosphere on the Earth was predominantly composed of CO2 and other partially oxidized gases such as CO, N2, and mixtures of reduced gases involving H2, CH4, NH3, and H2S. These gases were widely considered to have been the first reductant for anoxygenic photosynthesis. Studying the origins of photosynthesis is challenging as it emerged within ancient bacterial lineages. Our understanding of the origin of photosynthetic reaction centers and the evolution of cyanobacteria have been redefined by recent development in the genomic and molecular studies. Cyanobacteria appeared on Earth during the Archean and Proterozoic eras about 2.7 billion years ago and are widely considered to be the most significant group of photoautotrophic organisms. With limited resources, cyanobacteria started to utilize water to generate oxygen and were chiefly responsible for the creation of our planet’s oxygen-rich atmosphere and also contributed to the transformation of the environment on land and oceans. Cyanobacteria were the photosynthetic partner in the primary endosymbiotic event that introduced photoautotrophy to eukaryotes and higher plants. Moreover, they are essential topsoil microorganisms and play a key role in preventing soil erosion, and carbon and nitrogen fixation with numerous industrial applications.

Keywords

Cyanobacteria; photoautotrophs; primitive environment; oxygen; endosymbiosis

1.1 Introduction

The cyanobacteria can be found anywhere on planet’s surface including hot springs, hypersaline regions, subfreezing climates, and deserts. Cyanobacteria are morphologically complex prokaryotes, ranging from unicellular to filamentous forms with varying cellular and physical characteristics of cyanobacteria indicating that both bacteria and cyanobacteria descended from a common, chlorophyll-containing prokaryotic ancestor (Olson, 2001). While trying to piece together what led to the oxygenation of the planet, it is crucial to have an insight into the roots of oxygenic photosynthesis and the emergence of cyanobacteria (Sánchez-Baracaldo & Cardona, 2020). They are the first to colonize nutrient-poor environments such as bare rocks, newly piled dirt or ground after natural catastrophes, exposed walls, and partially completed structures. They thrive in places that most other animals would find uninhabitable, such as dirty water bodies, sewers, and rubbish dumps. These autotrophic prokaryotes must have inherited their adaptability from their pioneering ancestors, who once ruled the harsh, prehistoric Earth. Therefore these primitive prokaryotic creatures might be referred to as Pioneers of Planet Earth (Kulasooriya, 2011).

The primitive environment was largely anaerobic and gradually changes into an oxygen-rich atmosphere. The transition from an anoxygenic to an oxygenic environment was a slow and critical event in the history of life on Earth, shaping the evolution of life and the development of the planet. This transition could have been driven by several factors, including the evolution of photosynthetic organisms, the availability of resources, and changes in the environment. Cyanobacteria played a key role in creating an oxygen-rich atmosphere. Moreover, they formed symbiotic relationships with plants, fungi, and other organisms, which provide them with nutrients and also protected them from environmental stressors.

Eukaryotic algae and higher plants chloroplasts acquired the photosynthetic machinery via endosymbiotic interactions with cyanobacteria (Raven & Allen, 2003), which in turn prompted the evolution of oxygen-tolerant species. The rapid evolution of these organisms ensured that oxygenic and aerobic species would eventually dominate Earth’s biodiversity. Several species, each with its unique ecological requirements, have evolved in response to the specifics of their original habitat (Thomas et al., 2001).

1.2 Atmosphere on primitive Earth

The atmosphere of primitive Earth was much different from what we see today, with extreme temperatures, frequent changes in the environment, and high levels of methane, ammonia, and other gases. Primitive Earth was formed around 4.5 billion years ago, and for the first billion years, it was a hostile environment, with high temperatures, frequent impacts from asteroids and comets, and a lack of atmosphere. The first forms of life emerged around 3.5 billion years ago. The earliest life forms on Earth were simple, single-celled organisms. These organisms were able to thrive in the early environment due to their ability to survive in extreme conditions and their ability to perform simple metabolic processes. By colonizing the surface of rocks and other substrates, these organisms helped to create the first soils, which provided a habitat for other forms of life to thrive. Over the time, these simple organisms evolved and became more complex, leading to the development of multicellular organisms, such as algae, fungi, and eventually plants and animals.

Earth’s oceanic and terrestrial ecosystem came into existence between 4.8 and 4.5 billion years ago. The planet began to cool down, consolidate and became more stable. In the prebiotic soup, it is hypothesized that chemical or abiotic evolutionary processes occurred throughout the succeeding billion years, leading to the emergence of the first simple creatures capable of replicating themselves and this would have happened as a consequence of chemical evolution (Kulasooriya, 2011). The oldest known fossil evidence of life was discovered 3.5 billion years ago, or 1 billion years after the factual origin of Earth. Before 3.8 billion years ago, the possibility of life on Earth was extremely low (Nisbet & Sleep, 2001). For more insights into the origin of life, we need to look back to the Hadean era, which took place around 4.6 billion years ago and was marked by thick oceanic crust and volcanoes throughout a huge portion of the Earth (Fig. 1.1) (Moorbath, 2005). A high concentration of carbon dioxide made the atmosphere completely oxygen-free (Westall, 2005). None of the current theories for Earth’s atmosphere formation involving volcanic outgassing, hydrothermal activity, glaciations, and massive bombardment is entirely satisfactory to researchers. After studying Cr isotope deposits in rocks that are 3.2–3.5 Ga old, some scientists have hypothesized that life on other planets could be possible (Lowe et al., 2003). It is possible that direct evidence for early enumerations of life could have been lost due to plate tectonics (Westall, 2005). Nonetheless, chert and other geological records show that the Earth underwent several chemical changes between 4.6 and 3.8 Ga that ultimately determined its form (Daniel et al., 2006).

Figure 1.1 A timeline illustrating the beginning of life and the evolution of oxygen in the atmosphere.

The Hadean is the name given to the time of Earth’s history between 4.56 and 4.0 Ga, the Early Archean to the period between 3.2 and 2.8 Ga, the mid-Archean to the period between 2.8 and 2.5 Ga, and the late Archean to the period between 2.8 and 2.5 Ga (Westall, 2005). The primitive environment was shallow and scorching. To survive in the harsh environment, the early cells probably feed on both organic molecules already existing in the primordial soup and those made by other creatures, making them heterotrophs (Meierhenrich et al., 2010). Selected microbes were able to grow and duplicated their RNA at 80°C or higher. Volcanic outgassing or bursting of volcanic vents released methane, carbon dioxide, and hydrogen gases into the atmosphere. Comets and meteorites could also be a possible explanation for the prevalence of those gases (Nunn, 1998). However, levels of CH4 began to decrease and were converted into CO2 by photolysis. This CO2 ultimately turned into higher hydrocarbons or was deposited into rocks in the form of carbonate. In addition to those, NH3 and N2 were also detected in the atmosphere (Lazcano et al., 1983).

1.3 Archean life

Following the Hadean period is the more renowned Archean age, which holds the deepest mysteries of undiscovered life’s existence even today. In the beginning, there was more water than land on Earth. Most microscopic organisms have preferred the oceans to thrive and multiply. The water content of the atmosphere gradually decreased as a result of chemical reactions involving many gases. The ancestor of bacteria became mutated, possibly by unfavorable environments or intraspecific competitions. After that, they did not even acquire the ability to breach lands or rocks but also got favored and naturally selected. Simple spherical cells were the first form of life in the Archean period, although they fused to produce filaments, vibroids, and even some rods (Schirrmeister et al., 2016; Westall, 2005). It is challenging to conclude that cyanobacteria were extant in early Archean times due to the lack of evidence for trichome formations and cell differentiations. However, this does not mean that cyanobacteria were not present; data might have been misconstrued or lost. Further, microfossils recovered from biofilm mats attached to pyrite (a reduced mineral) display features not reported in cyanobacteria. Moreover, mineralogical evidence for oxidized minerals may point to nonoxygenic photosynthesis, perhaps because the organism was only able to extract an electron from H2S or lacked the machinery to utilize H2O. Chloroflexus, a modern anoxygenic photosynthetic bacterium in contemporary habitats, has a morphology that is visually similar to that of the filamentous mats seen in littoral zones (Prieto-Barajas et al., 2018). It has been theorized by geologists and paleontologists that cyanobacterial stromatolites are found in rocks from the late Archean and Proterozoic eras. However, this is subject to debate because stromatolites are not unique to cyanobacteria and can be formed by other nonoxygenic photosynthetic organisms as well (Westall, 2005).

New, life-supporting continents with sufficient mass emerged throughout the middle to late Archean era. South Africa’s 2.9 Ga Mozaan Group of the Pongola Supergroup provided the sediment surfaces with the evidence for the earliest filamentous cyanobacterial masses (Noffke et al., 2003; Olson, 2006). The Pilbara region of Australia has fossils that show the evolution of cyanobacteria through time (Brocks et al., 2003). Cyanobacteria were primarily responsible for the creation of an oxygen-rich atmosphere about 3.0 to 2.8 billion years ago (Ohmoto & Watanabe, 2004) The oxygen that we breathe today was previously produced by these bacteria. Elevated oxygen levels in the environment are characterized by several distinct processes, including the oxidation of iron, banded iron formations (BIFs) (Arculus & Delano, 1980), and the deposition of sulfate on the continental shelf (Cameron, 1982) and oxygen catastrophe (Fanale, 1971).

1.4 The first phototrophs: bacteria versus cyanobacteria

The chemoautotrophy, photoautotrophy, and organography processes provide energy, which is then used by cellular forms of life to carry out metabolic processes. These processes include active transport, movement of the cell, cell division, and the synthesis of the biochemical compound. It is believed that chemoautotrophic microorganisms emerged before photoautotrophic microorganisms. After subsequent evolutionary lines, organographic organisms emerged with the ability to oxidize stored organic material (Stadnichuk & Kusnetsov, 2021). Fischer et al. (2016) presented three hypotheses to understand the distribution of phototrophy in ancient times as well as the emergence of Photosystems I and II in cyanobacteria (Fig. 1.2).

Figure 1.2 Representation of hypothetical models to understand the distribution of phototrophy in ancient times, structured after (Fischer et al., 2016; Hohmann-Marriott & Blankenship, 2011; Mulkidjanian et al., 2006; Sousa et al., 2013; Xiong & Bauer, 2002).1. Selective loss model. 2. Cyanobacteria origin model. 3. Fusion model; 2 ideas represented (A) Fischer et al. (2016); (B) Xiong and Bauer (2002).

1.4.1 Selective loss model

The presence of both types I and II reaction centers in ancient phototrophs was the primary presumption of the selective loss concept (Fischer et al., 2016; Hohmann-Marriott & Blankenship, 2011). It is hypothesized that all other phototrophs descended from a single progenitor. Anoxygenic phototrophs lost one or both of the reaction centers while cyanobacteria conserved both of them. Genes required in phototrophic processes are mostly passed vertically from one generation to another.

1.4.2 Cyanobacteria origin model

The fundamental elements of this concept involve the discovery of phototrophy by ancestral cyanobacteria and the subsequent divergence of the ancestral reaction center into types I and II within this clade (Mulkidjanian et al., 2006; Sousa et al., 2013; Fischer et al., 2016). Later on, different organisms received the photosynthetic reaction center RCI or RCII via the process of lateral gene transfer.

1.4.3 The fusion model

Key features of the fusion theory include the evolution of reaction centers in distinct evolutionary branches. There are numerous different perspectives on this idea, with some suggesting that cyanobacteria developed from phototrophic ancestors and later acquired only PS-II (RCII) and others suggesting that cyanobacteria originated from nonphototrophic ancestors by receiving one reaction centers RCI from heliobacterium and RCII from a proteobacterium (Fischer et al., 2016). In 2002 Xiong and Bauer suggested a new theory on the fusion hypothesis, proposing that reaction centers had evolved from cyt-b-like proteins and then diverged across other bacterial phyla. RCII descended from cyt-b similar proteins and has branched off into three separate lineages. Cyanobacteria and green filamentous bacteria directly received the RC-II from the purple bacterium, however, RCII with the addition of CP47/CP43 formed a new lineage RCI which was eventually inherited by cyanobacteria and green sulfur bacterium (Xiong & Bauer, 2002).

Data from sequencing is not sufficient to determine the direction of lateral gene transfer of photosynthetic genes; additional evidence from many independent sources is required. Geological evidence may provide significant insights into the nature of the first phototrophs. Tice and Lowe suggest that photoautotrophic microbial populations about 3.4 Ga ago were chiefly responsible for depositions on the Buck Reef Chert which is 250–400 m thick rock that extends along the South African coast (Olson, 2006; Tice & Lowe, 2004). Additionally, they observed no indications of life at water depths greater than 200 m. Based on carbon isotopic content, Tice and Lowe classified the first microbes as partly filamentous phototrophs that fixed CO2 through the Calvin cycle. Because oxidized iron and sulfur were not found in the sediments, it was inferred that neither iron nor sulfide had been employed as possible electron donors. This analysis suggests atmospheric hydrogen as the candidate with the highest probability of serving as an electron donor. Phototrophic organisms retrieved from the Buck Reef Chert are unlikely to have descended from Gram-positive (Heliobacillus) or green sulfur (Chlorobium) phototrophs since these organisms do not utilize the Calvin cycle for CO2 fixation. The Calvin cycle is absent from Chloroflexus aurantiacus as well. Oscillochloris trichoides and some member of the green nonsulfur bacterium have been shown to utilize this cycle. Chloroflexi and purple bacteria possess RCII, but it serves no use in a hydrogen-driven metabolism. According to Olson, RCII makes use of a quinone as the last electron acceptor. Because of this, it would be over-reduced and kinetically incompetent if these circumstances were allowed to persist. As a result of these studies, the progenitors of cyanobacteria are the only known phototrophs that might have lived in the Buck Reef Chert around 3.4 billion years ago. These findings suggest that the first phototrophs were the anoxygenic pro-cyanobacteria that evolved into modern photosynthetic cyanobacteria; furthermore, the presence of cyanobacteria-specific biomarkers (2-methylhopanoides) from the 2.7-Gyrold sediments is another definite evidence. However, this can be questioned because these chemical biomarkers can be produced from nonphotosynthetic organisms.

1.5 Modern phototrophic genera

Currently, seven recognized bacterial phyla such as Proteobacteria, Chloroflexi, Chlorobi, Firmicutes, Acidobacteria, Gemmatimonadetes, cyanobacteria, and the recently discovered Candi-datus Eremiobacterota are phototrophic (Table 1.1) (Fischer et al., 2016). The phylum Proteobacteria encompasses a diverse range of microorganisms found in contemporary habitats. This phylum is often subdivided into the classes Alpha-, Beta-, and Gammaproteobacteria. All known phototrophs use an electron transport chain that includes RCII, bacteriochlorophyll a or b, Ubiquinone/Menaquinone, and a cytochrome bc1 complex. However, phototrophy is shown by only a few members of this genera (Bryant & Frigaard, 2006).

Table 1.1

The majority of Chloroflexi species are nonphototrophic, although it has been argued that they were formerly characterized as phototrophic species (Overmann, 2008). Reaction center II, bacteriochlorophyll a or c, and menaquinone can be seen in the genome of photosynthetic members of this clade. Although a cytochrome bc complex is not encoded in the C. aurantiacus genome (Yanyushin et al., 2005). It has been proven that this strain utilizes an ACIII for phototrophic growth. Klatt et al. (2011) identified an Anaerolineae class from a hot spring, Yellowstone National Park, and concluded that there are chances of increased diversification in coming years.

New findings have broadened the metabolic diversity of Chlorobi, which was previously classified as a phototrophic clade of stringent anaerobes (Imhoff, 2014). Studies on newly isolated and characterized nonphototrophic strains of Chlorobi, Ignavibacterium album (Iino et al., 2010; Liu et al., 2012), and Melioribacter roseus (Podosokorskaya et al., 2013) suggest that the phylum is not ancestrally phototrophic. Reaction center I, bacteriochlorophylls a, c, d, and e and chlorophyll a, cytochrome bc complex, and menaquinone, present in photoautotrophic members of the Chlorobi. The reverse tricarboxylic acid cycle is widely used for carbon fixation.

In contrast to all other types of phototrophs, heliobacteria are unique as they perform photosynthesis without any antennae proteins for light gathering. These organisms belong to a subset of photo-heterotrophic clostridia within the phylum Firmicutes (Fischer et al., 2016; Heinnickel & Golbeck, 2007; Sattley & Blankenship, 2010). During the process of photosynthesis, the members of this group utilize an RCI, bacteriochlorophyll g, a cytochrome bc complex, and menaquinone (Sattley et al., 2008).

Acidobacteria is one of the most widely dispersed and varied groups of organisms. They are most common in acidic soils, peatlands, and environments that are rich in mineral iron. Chloroacidobacterium thermophilum, a phototrophic acidobacterium, was identified in Yellowstone in 2007 (Bryant et al., 2007). Characterization of its genome and physiology revealed that it is a photo-heterotroph capable of utilizing several metabolic pathways (Fischer et al., 2016; Garcia Costas et al., 2012a, 2012b). They employ RCI that contains bacteriochlorophyll a, chlorophyll a, zinc-bacteriochlorophyll, menaquinone, cytochrome bc complex, and an ACIII (Garcia Costas et al., 2012b).

Members of Gemmatimonadetes are ubiquitous presence, however, little is known about their physiology, ecology, or role in environmental processes. Even though some insights into the Gemmatimonas genus may be gained through the study of Gemmatimonas sp. AP64, which was isolated from a freshwater lake in China (Zeng et al., 2014). Phylogenetic analysis of photosynthetic gene clusters of Proteobacteria and Gemmatimonadetes has shown conclusive evidence for the interphylum lateral gene transfer of phototrophy. To produce energy, Gemmatimonas sp. AP64 relies on RCII, bacteriochlorophyll a, menaquinone, cytochrome bc complex as well as ACIII (Fischer et al., 2016).

All known phototrophic cyanobacteria perform oxygenic photosynthesis, except two phylogenetically derived algal symbionts (Fischer et al., 2016; Nakayama et al., 2014; Tripp et al., 2010). Indeed, the total number of genes involved in photosynthesis in cyanobacteria is much greater than in other prokaryotic phototrophs. Only cyanobacteria possess photosynthetic reaction centers of both types, RCI and RCII. They have chlorophyll and phycobilin-containing light-harvesting systems (Fischer et al., 2016).

Candidatus Eremiobacterota is a newly discovered anoxygenic bacterial phylum. They thrive in cold, acidic, and aerobic environments and harness solar energy for their metabolic process. RCII, bacteriochlorophyll a, cyt-bc, and menaquinone can be seen in these genera (Ward et al., 2019).

1.6 The transition from an anoxygenic to an oxygenic environment

It is undeniable that the process of photosynthesis began a very long time ago; yet, there is a chance that concrete evidence of how this essential biological phenomenon first emerged and evolved with time may eventually be lost. Nevertheless, significant data might be acquired from a range of sources, most notably geology, biogeochemistry, comparative biochemistry, and studies of molecular evolution, which begins to provide some insights into the convoluted evolutionary history of photosynthesis (Olson, 2001). Hartman and Mauzerall presented the idea that photosynthesis developed over time, most likely beginning in the prebiotic period, and is inextricably linked to the origin of life (Hartman, 1998; Mauzerall, 1992). Meyer et al. (1996) and Nitschke et al. (1998) did not accept the theory proposed by Mauzerall (1992) and Hartman (1998) because they believed that photosynthesis developed later from bacteria performing anaerobic respiration with DNA, electron-transport proteins, and ATP synthase an integral part of their genome. Therefore they infer that bacterial photosynthesis evolved after bacteria split off from extremophiles (Archaebacteria).

Olson (2006) proposed several paths for photosynthesis origin based on fossil data from the Archean era. It is possible that hydrogen was the first reductant used in photosynthesis. Since there would not have been any selective pressure for oxygenic photosynthesis in the presence of hydrogen. The carbon isotope composition that was measured in graphite from the 3.8-Ga Isua Supercrustal Belt in Greenland is attributed to H2-driven photosynthesis rather than oxygenic photosynthesis. There is a possibility that anoxygenic photosynthesis contributed to the formation of the filamentous mats that were discovered in the 3.4-Ga Buck Reef Chert in South Africa (Tice & Lowe, 2004). H2S was likely another early reductant that was used. Later on, the generation of CH4 by methanogens is likely to have reduced the amount of H2 that was available in the atmosphere. The availability of H2S has also been limited to particular habitats close to volcanoes. Evaporites, putative stromatolites, and microfossils discovered in the Warrawoona formation are 3.5 billion years old. The mega sequence that has been found in Australia has been linked to sulfur-driven photosynthesis. The ability to utilize ferrous iron as a reductant is thought to have originated in proto-cyanobacteria and proteobacteria around 3.0 billion years ago or before. This form of photosynthesis could have led to the production of BIFs that are analogous to those brought about by oxygenic photosynthesis. Certain modern species of cyanobacteria that display light-driven CO2 fixation by cyclic photophosphorylation under anaerobic circumstances and utilizing electron donors such as H2S, thiosulfate, or even molecular H2 can provide evidence that such ancient mechanisms are still being used presently. Microfossils, stromatolites, and chemical biomarkers in Australia and South Africa reveal that oxygenic photosynthesis was carried out by cyanobacteria 2.8 billion years ago. However, the amount of oxygen in the atmosphere did not begin to grow until around 2.3 billion years ago.

The geological evidence available for early phototrophs traits suggests that photosynthesis may have originated in the cyanobacterial lineage due to UV light selection pressures and a paucity of electron suppliers (Mulkidjanian et al., 2006). Mulkidjanian also suggests that the first phototrophs were anaerobic cyanobacterial forerunners known as pro-cyanobacteria. These organisms carried out anoxygenic photosynthesis utilizing a reaction center closely resembling Photosystem I. The process of photosynthesis first developed in pro-cyanobacteria but has since spread to other taxa via the process of lateral gene transfer.

The discovery of chemical biomarkers known as 2-methylhopanoids in ancient rocks provides irrefutable evidence that organisms with characteristics similar to cyanobacteria existed even before 2.5 billion years ago. However, it is not possible to conclude purely based on the biomarkers whether or not the cyanobacterial ancestors engaged in oxygenic photosynthesis (Olson, 2001).

1.7 Early evolution of cyanobacteria

Throughout the years, detailed observations on cyanobacteria morphology, development, behavior, and ecological distribution have supported the argument that highly diversified cyanobacteria dominated the oceanic waters of the Proterozoic era (Knoll & Golubic, 2008). Cyanobacteria are classified into five subsections (Rippka & Herdman, 1985).

Subsection I (order Chroococcales) consist of solitary and colonial unicellular cyanobacteria, such as Synechococcus and Gloeocapsa. Both the life cycle and the taphonomic modification of Group I cyanobacteria have been extensively documented, which is a substantial indication of their abundance in Proterozoic ecosystems (Knoll & Golubic, 2008; Knoll & Golubic, 1979). Kazmierczak and Altermann (2002) found fossils of single-celled cyanobacteria (chroococcaleans) in South Africa that date back 2.5–2.6 Ga.

Subsection II (order Pleurocapsales) is comprised of cyanobacteria that range from unicellular to pseudo-filamentous. They are capable of forming thallus and employing both binary fission and multiple modes of reproduction. Group II cyanobacteria are represented by the ca. 800-million-year-old Palaeopleurocapsa with its name highlighting a close similarity to extant Pleurocapsa (Knoll & Golubic, 2008).

Subsection III (order Oscillatoriales) comprises filamentous forms without any specialized cells of differentiation. The silicified fossil assemblages throughout the Proterozoic record could indicate the prevalence of Oscillatoria, Lyngbya, Spirulina, and Microcoleus during that period. Although similar fossils may be produced by other bacteria such as photobacteria and sulfur-oxidizers, however, the environmental distribution supports the existence of Group III cyanobacteria (Schopf & Klein, 1992).

Specialized cells such as akinetes and heterocysts (Anabaena, Nostoc) are peculiar in subsections IV (order Nostocales). Subsection V (order Stigonematales) consists of filamentous forms that have a more complex multicellular organization. It is challenging to track the heterocyst differentiating cyanobacteria because heterocysts degrade quickly. However, compelling evidence comes from Stigonema-like fossils that are preserved in the ca. 400 Ma Rhynie Chert, Scotland (Croft & George, 1959; Knoll & Golubic, 2008). Akinetes, on the other hand, have a high probability of survival in the geological record, and massive, elongate microfossils from the Mesoproterozoic (1600–1000 Ma) cherts (Knoll & Golubic, 2008; Srivastava, 2005) have been interpreted as nostocalean akinetes. The first fossils definitively identified as akinetes are found in rocks from Australia dating back to around 1650 Ma (Knoll & Golubic, 2008; Tomitani et al., 2006) whereas the earliest candidate in which akinetes are found in cherts from Gabon dating back to approximately 2100 Ma (Amard & Bertrand-Sarfati, 1997). Scytonema sheaths, with their signature funnel-inside-a-funnel structure, may be seen in cherts from the middle Proterozoic of Siberia (Knoll & Golubic, 2008; Sergeev et al., 2002).

The cyanobacteria fossil record does not provide definitive evidence for the origin of oxygenic photosynthesis (Schirrmeister et al., 2016), and molecular biomarkers are unreliable as well (Rasmussen et al., 2008). According to geochemical evidence, the initial increase in atmospheric oxygen, or the great oxidation event (GOE), occurred between 2.32 and 2.4 billion years ago (Bekker et al., 2004; Lyons et al., 2014; Sánchez-Baracaldo & Cardona, 2020). It is possible that oxygenic photosynthesis and oxygen-dependent metabolic and biosynthetic pathways first originated and diversified during the great oxygenation event (Raymond & Segrè, 2006). Around 800 to 600 million years ago, there was another large oxygenation event called the Neoproterozoic oxidation event (NOE) that led to elevated levels of oxygen in the environment (Scott et al., 2008; Sánchez-Baracaldo & Cardona, 2020) significant glacial events, and enormous disturbances to the carbon cycle (Lyons et al., 2014). The accumulation of O2 in the atmosphere has begun when the rate of carbon fixation by oxygenic phototrophs surpassed the rate of respiration of organic matter. Both carbon depletion and organic carbon burial in ocean sediments are consequences of the imbalance between these two processes (Holland, 2006).

1.8 Photosynthetic apparatus

The process of photosynthesis is categorized into two forms: oxygenic photosynthesis and nonoxygenic photosynthesis. The organism utilizing the process is called oxygenic phototrophs and nonoxygenic phototrophs. These classifications are based on the type of end terminal acceptor used and the release of oxygen. Oxygenic phototrophs employ two photosystems: Photosystem I (PSI) and Photosystem II (PSII), however, anoxygenic photoautotrophs only possess a single photosystem, either PSI or PSII.

The reaction centers, antenna complexes, electron transport complexes, and carbon fixation machinery are the essential components that make up the photosynthetic apparatus. It is certain that the evolutionary paths of these components have diverged among different organisms, suggesting the mosaic nature of the photosynthetic apparatus from several substructures with distinct origins and histories (Olson, 2001). The primary step for photosynthesis involves capturing light by light-harvesting complexes followed by the transfer of excited electrons to the photosynthetic reaction centers, and the major charge separation occurs across the photosynthetic membrane. The reaction center of PSI is responsible for the stabilization of the excited electron by Fe/S centers and through the mediation of the pheophytin/quinone cluster in the PSII reaction center (Stadnichuk & Kusnetsov, 2021).

1.9 Photosystems I and II

D1 and D2 are the core component of cyanobacterial PSII. These proteins are linked to CP43 and CP47 (Chl a-binding proteins) antenna subunits. These components originated from an ancient gene duplication event. Each RCII has one CP43 and CP47 subunit. PsaA and psaB proteins are the core components of PSI (Olson, 2001).

Helices VI of CP47 and PshA (subunit of PS-I) of heliobacteria showed a resemblance (Vermaas, 1994), whereas the N-terminal half of PshA (helices I–VI) has a significant similarity with helices I–IV of CP47. These similarities provide significant evidence for the evolutionary relationship between PshA and PSII. Furthermore, CP43 exhibits strong sequence similarities to the pcb antenna complexes from prochlorophytes and the isiA antenna complexes (also named CP43) from iron-stressed cyanobacteria (Olson, 2001; Olson & Blankenship, 2004; Rutherford & Faller, 2003).

Ancestral photosystems were homodimeric. Both RC1 and RCII function together in the Z-scheme for transferring electrons from Fe (OH)+ to NADP+, whereas cyclic electron flow was independently driven by RCI or RCII during ATP synthesis. In the course of evolution that led to the genesis of proteobacteria, RC1, and the chlorophyll protein were both lost, while RCII was preserved and transformed into a heterodimeric form. In the line leading to cyanobacteria, both RCI and RCII replaced bacteriochlorophyll a with chlorophyll a and became heterodimeric. Further coevolution between heterodimeric RCII and a complex containing Mn resulted in the use of water as the electron donor for CO2 fixation.

The evolution of reaction center protein families sheds light on the origin of photosynthetic water oxidation (Cardona, 2019; Sánchez-Baracaldo & Cardona, 2020). At the organismal level, phylogenomic methods were used to trace the origins of organisms performing oxygenic photosynthesis (Schirrmeister et al., 2016). By combining the two methods, scientists have been able to reconstruct biological occurrences that had been lost for almost 3 billion years. One possible explanation for the dramatic split between oxygenic and anoxygenic photosystems is the necessity to manage with oxygen (Cardona, 2019; Orf et al., 2018). Thus the first steps in the oxidation of water and release of oxygen may have occurred simultaneously with the development of the two separate families of reaction centers (Cardona, 2019; Rutherford & Faller, 2003; Sánchez-Baracaldo & Cardona, 2020).

The core proteins of PSII, which are involved in oxygenic photosynthesis, are thought to have originated in the Paleoarchean period between 3.6 and 3.2 billion years ago, while the last common ancestor of modern cyanobacteria, which dates from between 3.2 and 2.8 bya, originated in the Mesoarchean period (Sánchez-Baracaldo et al., 2022). Reaction center proteins have been structurally and genetically analyzed, and these findings reveal that all phototrophs have a common origin. According to the phylogenetic data, present photosynthetic organisms descended from a single ancestor, however, a closer study of the bacterial tree of life reveals that there is no evidence that any of the surviving phototrophs have a common phototrophic ancestor. Because of these discrepancies, more research is required to determine the specific evolutionary pathways that have resulted in the observed diversity of photosynthetic bacteria (e.g., lateral gene transfer, gene duplication, and differential loss Sánchez-Baracaldo & Cardona, 2020).

1.10 Higher plant chloroplast inheritance via endosymbiosis

The exploration of the chloroplast symbiogenesis hypothesis is often regarded as the 20th century’s crowning achievement in biological science and crucial in understanding how cells have evolved. This emerging scientific discipline, known as symbiogenetics, studies the building blocks of life, including symbiogenesis, parallel gene transfer, and signaling intra- and intercellular linkages. Numerous fascinating phrases have been used to describe chloroplast symbiogenesis, such as purchased products for eukaryotes (Larkum, 2003), little green slaves of the cell (Mereschkowsky, 1905), and eaten but not digested (Keeling, 2010).

During the Precambrian, 2200 to 1200 million years ago, the first endosymbiotic event, also known as Merezhkowsky’s symbiogenesis, may have occurred (Kutschera & Khanna, 2022). Schimper and von Zittel (1885) based on his observations on chloroplast’s ability to divide and pass genetic information from one generation to the next suggested that chloroplasts could have evolved from cyanobacteria. The electron microscopy and molecular biology findings from the early 1960s provided a skewed view of the endosymbiosis idea. Nevertheless, Margulis (1970) was chiefly responsible for its widespread acceptance in the 1970s. The idea that chloroplasts evolved endosymbiotically through cyanobacteria is now widely accepted as a cornerstone of modern biology. It is well-established that some primitive eukaryotic cells phagocytosed cyanobacteria, paving the way for the development of eukaryotic photosynthesis (Lazcano & Peretó, 2017). Genome comparisons between cyanobacteria and plastids provide compelling evidence for a phyletic initial endosymbiosis between them. This includes similarities in genome structure, coding capacity, gene organization, content, and sequencing.

Many proteins essential to plant growth and development are encoded by genes that were first developed in cyanobacteria. It is a well-established fact that plastids contain a far higher number of proteins than their relatively small genomes are even capable of encoding. It has been hypothesized that these proteins were initially encoded in the genome of the endosymbiont, but later they transferred to the nucleus of the host organism during the initial stages of endosymbiosis.

The enzyme phosphoglycerate kinase (PGK) is encoded in the nucleus of higher plants in two different isoforms, one of which is plastid-localized and the other of which is cytosol-localized. Both PGK isoforms originated in cyanobacteria, even though the cellular compartments in which they operate have diverged through time. An apparent duplication of the cyanobacterial PGK gene occurred throughout plant evolution, with one copy serving the plastid and the other assuming the function of a previously existing (noncyanobacterial) cytosolic protein hence referred to as endosymbiotic gene replacement.

The cyanobacterial outer membrane has been shown to include evidence of additional links between cyanobacteria and the chloroplasts of plant cells. The outer membrane often includes a repertory of carotenoids that is unique to the species, in addition to a variety of lipids and proteins. The presence of these carotenoids in the chloroplast outer envelope membrane lends credence to the idea that this plastid envelope can be a remnant from the endosymbiotic process that ultimately resulted in the evolution of the chloroplast. It is possible that carotenoids’ resilience to high light intensity, especially in the UV spectrum, protected cyanobacterial cells from damage. This suggests that the effects of endosymbiosis on the host were far greater than the mere acquisition of an organelle as an outcome of this process.

It is possible that the development of eukaryotic cell mitochondria, the energy centers of eukaryotic cells, delayed chloroplast endosymbiosis (Kowallik & Martin, 2021). Endosymbiosis was beneficial for both partners. The oxygen produced by the cyanobacterial metabolism is used by the mitochondria, while the carbon dioxide released into the cytoplasm is taken in by the ingested cyanobacteria. Proeukaryotes were given a better chance of surviving, thanks to mitochondria’s use of oxygen after the oxygen catastrophe event, which was brought on by cyanobacteria in the ecosystem 2.45 billion years ago. Oxidative damage to organelles might be caused by an excess of molecular oxygen in the low-aerobic cytoplasm, which could lead to the production of reactive oxygen species (ROS). Because the chloroplast evolved multiple ROS deactivation mechanisms, the ternary system consisting of chloroplasts, cytosol, and mitochondria has become a stable form of life (Stadnichuk & Kusnetsov, 2021).

The question of whether all chloroplasts developed from a single fundamental endosymbiotic event or a succession of events has long been discussed. The initial endosymbiotic event differs from secondary endosymbioses in that it involves the insertion of a eukaryotic alga into another cell. This has likely occurred several times, giving rise to a diverse range of eukaryotic algae groups (Palmer & Delwiche, 1996). Although the emergence of chloroplasts from cyanobacteria resulted in multiple dramatic structural changes, the underlying chemistry of oxygenic photosynthesis remained mostly the same (Olson, 2001).

1.11 Conclusion

Cyanobacteria emerged around 3.5 billion years ago. They began to photosynthesize and produce oxygen as a waste product. Cyanobacteria’s ability to produce oxygen has revolutionized the Earth’s atmosphere. They slowly changed the composition of the atmosphere, creating the environment that eventually allow the evolution of more complex forms of life. Despite their ancient origins, cyanobacteria are still widely distributed and play an important role in shaping our ecosystems. In this paper, we have traced the history of cyanobacteria and the origin of photoautotrophic microorganisms via geological and chemical data. Some insights can be given into how photosynthesis originated and developed on the primitive Earth, the transformation from anoxygenic photosynthetic bacteria to an oxygen-rich atmosphere through cyanobacteria and eventually to chloroplasts. In the future, if Earth experiences a global catastrophe that could wipe out all life, then cyanobacteria would be crucial in re-establishing life forms on a hypothetically barren Earth.

Acknowledgment

The authors are very much thankful to the Department of Microbiology, Central University of Rajasthan, Bandarsinndri for providing necessary facilities.

Competing interests

All the authors declare that they have no competing interests.

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