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Two subpopulations of C rocosphaera watsonii have distinct distributions in the N orth and S outh P acific
Author(s) -
Bench Shellie R.,
Frank Ildiko,
Robidart Julie,
Zehr Jonathan P.
Publication year - 2016
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.13180
Subject(s) - biology , phenotype , biogeochemical cycle , genome , gene , genetics , ecology
Summary C rocosphaera watsonii is a unicellular nitrogen ( N 2 )‐fixing cyanobacterium with ecological importance in oligotrophic oceans. In cultivated strains there are two phenotypes of C . watsonii (large and small cells) with differences that could differentially impact biogeochemical processes. Recent work has shown the phenotypes diverged through loss or addition of type‐specific genes in a fraction of their genomes, whereas the rest of the genomes were maintained at 99–100% DNA identity. Previous molecular assays for C . watsonii abundances targeted the conserved regions and therefore could not differentiate between phenotypes, so their relative distributions in natural communities were unknown. To determine phenotype distributions, this study developed and applied type‐specific quantitative polymerase chain reaction assays to samples from the N orth and S outh P acific. Abundances of both C rocosphaera types declined sharply with depth between 45 and 75 m in both sites. In surface water small cells were 10–100 times more abundant than large cells in the N . P acific, whereas in the S . P acific the two phenotypes were nearly equal. Evidence for large cell aggregation was only found in N . P acific samples. The differences in C . watsonii sub‐populations in the N orth and S outh P acific have direct implications for biogeochemistry and carbon export in oligotrophic gyres.