Cyanobacterial-Plant Symbioses

Reference work entry


Cyanobacteria are a large group of photoautotrophic prokaryotes found in almost every environment and frequently in great abundance, particularly in the oceans. They form symbiotic relationships with a broad range of eukaryotic hosts including plants, fungi, and animals such as corals, sponges, and ascidians (sea squirts). The plant and fungal symbioses are the subject of this chapter. Within the host, the cyanobacterial symbionts (cyanobionts) are protected from environmental extremes and predation, in turn supplying the host with fixed nitrogen and, in the case of nonphotosynthetic hosts, fixed carbon. Many cyanobacteria are facultative heterotrophs, enabling them to occupy regions of the host receiving little or no light, such as the roots of plants, where they receive fixed carbon from their photosynthetic partner. In the vast majority of these symbioses, the cyanobionts are capable of independent growth, but in symbiosis they often undergo morphological and physiological modifications. In many filamentous cyanobionts, nitrogen fixation occurs in specialized cells known as heterocysts which, in free-living cyanobacteria, constitute less than 10 % of total cells. In many plant and some lichen symbioses, the heterocyst frequency is elevated four- to fivefold, as is the rate of nitrogen fixation. A number of these symbioses are of major environmental importance as suppliers of fixed nitrogen to their surroundings. For example, moss associations with epiphytic cyanobacteria are abundant in northern hemisphere forests, and cyanolichens are abundant in harsh environments where there are few other sources of fixed nitrogen.


Glutamine Synthetase Arbuscular Mycorrhiza Lichen Thallus Heterocyst Frequency Nostoc Punctiforme 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.Faculty of Biological SciencesUniversity of LeedsLeedsUK
  2. 2.Department of BotanyStockholm UniversityStockholmSweden
  3. 3.Department of BiologyRensselaer Polytechnic InstituteTroyUSA
  4. 4.Department of BiochemistryNorth-Eastern Hill UniversityShillongIndia
  5. 5.Genetics Biocenter, University of MunichMunichGermany

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