%0 Journal Article
%9 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES
%A Bonnet, Sophie
%A Webb, E. A.
%A Panzeca, C.
%A Karl, D. M.
%A Capone, D. G.
%A Sanudo-Wilhelmy, S. A.
%T Vitamin B-12 excretion by cultures of the marine cyanobacteria Crocosphaera and Synechococcus
%D 2010
%L fdi:010081605
%G ENG
%J Limnology and Oceanography
%@ 0024-3590
%M ISI:000283667100014
%N 5
%P 1959-1964
%R 10.4319/lo.2010.55.5.1959
%U https://www.documentation.ird.fr/hor/fdi:010081605
%> https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers21-03/010081605.pdf
%V 55
%W Horizon (IRD)
%X Axenic cultures of the N-2-fixing marine cyanobacterium Crocosphaera watsonii exhibit very high B-12 excretion rates (up to 40 times higher per cell), compared to the smaller non-N-2-fixing strain of marine Synechococcus. The effect of N availability on vitamin synthesis is also evident in the non-diazotrophic strain, as they release five times more B-12 under N-replete conditions relative to N-limiting conditions, although this value is still an order of magnitude smaller than the amount produced by the diazotroph. The cyanobacterial contribution to the oceanic B-12 supply may be similar to 50 times higher than the contribution of heterotrophic bacteria. Oceanic cyanobacteria do not compete for exogenous B-12 with other prokaryotes and eukaryotes, but instead are obligate producers, thereby defining a unique dual ecological role for N-2-fixing cyanobacteria in the oligotrophic ocean. They provide both a source of "new' bioavailable nitrogen and the B-12 needed to support the growth of larger auxotrophic eukaryotic phytoplankton important for the biological carbon pump.
%$ 036