Marine cyanobacteria

Frédéric Partensky (1) , Wolfgang Hess (2) , Laurence Garczarek (1)

1 AD2M - Adaptation et diversité en milieu marin
2 University of Freiburg [Freiburg]

Although numerous marine prokaryotes dwelling in the sunlit layer of oceans can exploit solar energy, cyanobacteria are the only ones to perform oxygenic photosynthesis and to produce organic carbon, a critical process that sustains the whole marine trophic web. Here, we review the recent advances on marine cyanobacteria, with a special focus on the two most abundant genera of the ocean: Prochlorococcus and Synechococcus, which have been studied at all scales of organization from the gene to the global ocean. Both display a wide genetic and functional diversity intimately related to the ecological niches in which they thrive. Another ecologically important group of marine cyanobacteria are diazotrophs that, by their ability to fix atmospheric dinitrogen, constitute a major source of new nitrogen for the microbial community. Diazotrophic cyanobacteria are polyphyletic and display a remarkably large range of morphologies and lifestyles. These include both multicellular cyanobacteria, such as the colonial Trichodesmium or the heterocyst-forming Calothrix, Richelia and Nodularia, and unicellular cyanobacteria belonging to three major taxa: the symbiotic species Candidatus Atelocyanobacterium thalassa (UCYNA) and the free-living genera Crocosphaera watsonii (UCYN-B) and Crocosphaera subtropica (previously known as Cyanothece sp., UCYN-C). Whereas some of these organisms can form immense blooms (Nodularia, Trichodesmium), others such as UCYN-C can also have a significant ecological impact, even though they represent only a minor fraction of the phytoplanktonic community. After several billions of years of evolution, which led them to colonize most marine niches reached by solar light, cyanobacteria appear as truly fascinating organisms that constitute a major component of the marine microbial communities and are the matter of a thriving field of research. The considerable amount of omics data now available on both isolates and natural populations of marine cyanobacteria provides a solid basis for investigating their molecular ecology, contribution to biogeochemical cycles, as well as use for data mining and potential biotechnological applications, such as e.g. production of hydrogen, ethanol, alkanes or fluorophores.

Domaines: Biodiversité et Ecologie; Microbiologie et Parasitologie; Bactériologie

Frédéric Partensky, Wolfgang Hess, Laurence Garczarek. Marine cyanobacteria. Lucas J. Stal; Mariana Silvia Cretoiu. The Marine Microbiome, 3, Springer International Publishing, pp.103-157, 2022, The Microbiomes of Humans, Animals, Plants, and the Environment, 978-3-030-90383-1. ⟨10.1007/978-3-030-90383-1_3⟩. ⟨hal-03971447⟩