Tansley Review No. 107. Heterocyst and akinete differentiation in cyanobacteria
David G. Adams,Paula S. Duggan +1 more
TLDR
This review will concentrate on the heterocyst and the akinete, emphasizing the differentiation and spacing of these specialized cells in Cyanobacteria, an ancient and morphologically diverse group of photosynthetic prokaryotes.Abstract:
Summary 3
I. introduction 4
II. the cyanobacteria 7
III. the heterocyst 9
1. Function and metabolism 9
2. Heterocyst structure 12
(a) Overview 12
(b) The polysaccharide (homogeneous) layer 12
(c) The glycolipid (laminated) layer 12
(d) The septum and microplasmodesmata 12
3. Nitrogen regulation and heterocyst development 12
4. Heterocyst development 13
(a) The proheterocyst 13
(b) Proteolysis associated with heterocyst development 14
(c) RNA polymerase sigma factors 14
(d) Developmental regulation of heterocyst cell wall and nitrogenase gene expression 14
(e) Genome rearrangements associated with heterocyst development 15
5. Genes essential for heterocyst development 15
(a) hetR 15
(b) Protein phosphorylation and the regulation of hetR activity 16
(c) hetR in nonheterocystous cyanobacteria 16
(d) Other heterocyst-specific genes 16
6. Heterocyst spacing 18
(a) Patterns of heterocyst differentiation 18
(b) Genes involved in heterocyst spacing 18
(c) Disruption of heterocyst pattern 18
7. Filament fragmentation and the regression of developing heterocysts 20
8. The nature of the heterocyst inhibitor 20
9. Cell selection during differentiation and pattern formation 20
(a) Cell division 20
(b) DNA replication and the cell cycle 21
(c) Competition 21
10. Models for heterocyst differentiation and pattern control 21
IV. the akinete 23
1. Properties of akinetes 23
2. Structure, composition and metabolism 24
3. Relationship to heterocysts 24
4. Factors that influence akinete differentiation 24
5. Extracellular signals 25
6. Akinete germination 25
7. Genes involved in akinete differentiation 26
V. conclusion 26
Acknowledgements 27
References 28
Cyanobacteria are an ancient and morphologically diverse group of photosynthetic prokaryotes. They were the first organisms to evolve oxygenic photosynthesis, and so changed the Earth's atmosphere from anoxic to oxic. As a consequence, many nitrogen-fixing bacteria became confined to suitable anoxic environmental niches, because the enzyme nitrogenase is highly sensitive to oxygen. However, in the cyanobacteria a number of strategies evolved that protected nitrogenase from oxygen, including a temporal separation of oxygenic photosynthesis and nitrogen fixation and, in some filamentous strains, the differentiation of a specialized cell, the heterocyst, which provided a suitable microaerobic environment for the functioning of nitrogenase. The evolution of a spore-like cell, the akinete, almost certainly preceded that of the heterocyst and, indeed, the akinete may have been the ancestor of the heterocyst. Cyanobacteria have the capacity to differentiate several additional cell and filament types, but this review will concentrate on the heterocyst and the akinete, emphasizing the differentiation and spacing of these specialized cells.read more
Citations
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Eco-physiological adaptations that favour freshwater cyanobacteria in a changing climate
Cayelan C. Carey,Bastiaan Willem Ibelings,Emily P. Hoffmann,David P. Hamilton,Justin D. Brookes +4 more
TL;DR: This Review examines how several cyanobacterial eco-physiological traits, specifically, the ability to grow in warmer temperatures; buoyancy; high affinity for, and ability to store, phosphorus; nitrogen-fixation; akinete production; and efficient light harvesting, vary amongst cyanobacteria genera and may enable them to dominate in future climate scenarios.
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Biological nitrogen fixation in non-legume plants
TL;DR: Improved understanding of the molecular mechanism of BNF outside the legume-rhizobium symbiosis could have important agronomic implications and enable the use of N-fertilizers to be reduced or even avoided.
Journal ArticleDOI
Nitrogen fixation and photosynthetic oxygen evolution in cyanobacteria.
TL;DR: An analysis of the geochemical conditions under which nitrogenase evolved is presented and how the evolutionary history of the enzyme complex corresponds to the physiological, morphological, and developmental strategies for reducing damage by molecular oxygen is examined.
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Compartmentalized function through cell differentiation in filamentous cyanobacteria
Enrique Flores,Antonia Herrero +1 more
TL;DR: This Review addresses cyanob bacterial intercellular communication, the supracellular structure of the cyanobacterial filament and the basic principles that govern the process of heterocyst differentiation.
Journal ArticleDOI
Regulation of Cellular Differentiation in Filamentous Cyanobacteria in Free-Living and Plant-Associated Symbiotic Growth States
John C. Meeks,Jeff Elhai +1 more
TL;DR: The physiology of symbiotically associated cyanobacteria raises the prospect that heterocyst differentiation proceeds independently of the nitrogen status of a cell and depends instead on signals produced by the plant partner.
References
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Journal ArticleDOI
Generic assignments, strain histories, and properties of pure cultures of cyanobacteria
TL;DR: Revisions are designed to permit the generic identification of cultures, often difficult through use of the field-based system of phycological classification, and are both constant and readily determinable in cultured material.
Book
The Molecular Biology of Cyanobacteria
TL;DR: This work focuses on the study of the structure and function of the Photosystem II Reaction Center in Cyanobacteria, which consists of Chloroplast Origins and Evolution, and its role in the Evolution of the Universal Enzyme.
Journal ArticleDOI
Trichodesmium, a Globally Significant Marine Cyanobacterium
TL;DR: N2 fixation by Trichodesmium is likely a major input to the marine and global nitrogen cycle.
Book
The ecology of cyanobacteria: their diversity in time and space.
Brian A. Whitton,Malcolm Potts +1 more
TL;DR: This chapter discusses cyanobacteria in deserts: life at the limits?
Journal ArticleDOI
Phototrophic Prokaryotes: The Cyanobacteria
Roger Y. Stanier,G Cohen-Bazire +1 more