Globally Distributed Uncultivated Oceanic N2-Fixing Cyanobacteria Lack Oxygenic Photosystem II

@article{Zehr2008GloballyDU,
  title={Globally Distributed Uncultivated Oceanic N2-Fixing Cyanobacteria Lack Oxygenic Photosystem II},
  author={Jonathan P. Zehr and Shellie R. Bench and Brandon J. Carter and Ian Hewson and Faheem Niazi and Tuo Shi and H. James Tripp and Jason P. Affourtit},
  journal={Science},
  year={2008},
  volume={322},
  pages={1110 - 1112}
}
Biological nitrogen (N2) fixation is important in controlling biological productivity and carbon flux in the oceans. Unicellular N2-fixing cyanobacteria have only recently been discovered and are widely distributed in tropical and subtropical seas. Metagenomic analysis of flow cytometry–sorted cells shows that unicellular N2-fixing cyanobacteria in “group A” (UCYN-A) lack genes for the oxygen-evolving photosystem II and for carbon fixation, which has implications for oceanic carbon and nitrogen… 

Paper Mentions

Unicellular Cyanobacterial Distributions Broaden the Oceanic N2 Fixation Domain
TLDR
It is found that two major groups of unicellular N2-fixing cyanobacteria (UCYN) have distinct spatial distributions that differ from those of Trichodesmium, the N2+ cyanobacterium previously considered to be the most important contributor to open-ocean N2 fixation.
Nitrogen fixation by marine cyanobacteria.
  • J. Zehr
  • Biology, Medicine
    Trends in microbiology
  • 2011
TLDR
The major cyanobacterial groups have different physiological and ecological constraints that result in highly variable geographic distributions, with implications for the marine N-cycle budget.
Metabolic streamlining in an open-ocean nitrogen-fixing cyanobacterium
TLDR
It is found that UCYN-A lacks a number of major metabolic pathways including the tricarboxylic acid cycle, but retains sufficient electron transport capacity to generate energy and reducing power from light, and is dependent on other organisms for essential compounds.
Marine Non-Cyanobacterial Diazotrophs: Moving beyond Molecular Detection.
TLDR
The need for combining rate measurements and molecular analyses of field samples with cultivation studies in order to clarify the ecology of non-cyanobacteria and their contribution to marine N2 fixation on local and global scales is highlighted.
Oxygen and temperature in relation to nitrogen fixation in cyanobacteria: In the daily life of cyanobacteria
TLDR
The results described in this thesis reveal that unicellular diazotrophic cyanobacteria are unable to fix N2 under fully aerobic conditions and it is found that the O2 flux into the heterocyst is dynamically regulated by temperature.
Unicellular cyanobacteria with a new mode of life: the lack of photosynthetic oxygen evolution allows nitrogen fixation to proceed
TLDR
Sequence data show that Rhopalodia gibba and its spheroid bodies are an evolutionarily young symbiosis that might serve as a model system to unravel early events in the evolution of chloroplasts.
Process‐understanding of marine nitrogen fixation under global change
TLDR
Key processes in the CO2 response of Trichodesmium were shown to include a reallocation of energy between the carbon concentrating mechanisms and N2 fixation, as well as intracellular cycling of inorganic carbon.
Hopanoid lipids may facilitate aerobic nitrogen fixation in the ocean
TLDR
It is concluded that hopanoid-enriched membranes are a conserved trait in non−heterocyst-forming cyanobacterial diazotrophs that might lower the permeability to extracellular O2.
Diversity, Ecology, and Biogeochemical Influence of N 2 -Fixing Microorganisms in the Sea
TLDR
The genetic and metabolic basis for oceanic diazotroph diversity is reviewed and how this diversity impacts biogeochemical cycles is discussed and how changes to marine ecosystems might influence the future role of d Diazotophs in ocean ecology and biogeochemistry is discussed.
Unicellular Cyanobacterium Symbiotic with a Single-Celled Eukaryotic Alga
TLDR
It is shown that UCYN-A has a symbiotic association with a unicellular prymnesiophyte, closely related to calcifying taxa present in the fossil record, and this unusual partnership is a model for symbiosis and is analogous to plastid and organismal evolution, and may have important implications for past and present oceanic N2 fixation.
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