| Summary: | 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 Alphaproteobacteria and Gammaproteobacteria , while control and substrate amended incubations were dominated by Gammaproteobacteria or Bacteroidetes . Alphaproteobacteria dominated extended peat-amended incubations, with DNA sequences 99% similar to the Arctic Ocean Sulfitobacter (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 Sulfitobacter may be important in the degradation of terrestrial organic matter in the Arctic Ocean.
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