LINKING PHYLOGENY AND LIPID COMPOSITION OF NATURAL BACTERIAL COMMUNITIES IN ARCTIC WATERS
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The effects of organic matter on Arctic bacterioplankton community composition and lipid composition were studied in regrowth experiments amended with peat, ice algae and ice-rafted debris. Bacterial community composition was examined using length heterogeneity PCR, individual fatty acid, and intact phospholipid (IPL) analyses. The Inoculum contained rRNA genes identified as <em>Alphaproteobacteria</em> and <em>Gammaproteobacteria</em>, while control and substrate amended incubations were dominated by <em>Gammaproteobacteria</em> or <em>Bacteroidetes</em>. <em>Alphaproteobacteria</em> dominated extended peat-amended incubations, with DNA sequences 99% similar to the Arctic Ocean <em>Sulfitobacter</em> (ARK10278). Fatty acids synthesized in incubations overlapped, with 16:0n and 16:1D9 and 18:0n dominating, excluding the extended peat incubation where 16:1D9, 18:1D11 and 16:0n dominated. Phosphatidylglycerol and phosphatidylethanolamine were the only phospholipids observed using liquid chromatography mass spectrometry, with only subtle differences among distinct bacterioplankton communities in regrowth experiments. These results indicate that <em>Sulfitobacter</em> may be important in the degradation of terrestrial organic matter in the Arctic Ocean.