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doi:10.2204/iodp.proc.314315316.123.2009 MicrobiologySample informationA total of 38 whole-round cores were taken from Holes C0001E, C0001F, and C0001H for microbiological analysis. Table T21 shows the depths of the three types of whole-round cores. Some whole-round cores were subsampled on board for cell fixing, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) extraction, and culturing studies. Onboard work mainly included preserving whole-round cores and subsamples for shore-based work, fixing cells for cell detection and counting, and setting up enrichment cultures of sulfate-reducing bacteria. Cell detection with epifluorescence microscopyA total of 12 fixed cell samples were selected from the entire depth with roughly equal intervals and were stained with double-stranded DNA-binding SYBR Green I stain. Cells were detected in core samples from 0.5 to 448 m CSF (Table T22). Cells were rod, oval, and coccoidal in shape (Fig. F45). Cells were also detected in both seawater gel and kill mud, which shows that these drilling muds are a potential source of microbial contamination if mixed with sediment core material. In a control sample of 15 mL filtered phosphate-buffered saline and in a sediment sample without SYBR Green I staining, only a very few green particles were detected. Cultivation experimentsMore than 200 enrichment cultures were established during Expedition 315 with the aim to culture sulfate-reducing microorganisms. Cultures were monitored for sulfate reduction based on the formation of black iron sulfide precipitate, which indicates production of biogenic hydrogen sulfide in the iron-containing medium. During the expedition, blackening of the growth medium was observed in only a few sediment cultures incubated at 9° or 37°C and in seawater gel cultures incubated at 37°C. At 9°C, sulfate reduction was first observed after 3 weeks of incubation; at 37°C, some cultures turned dark within 1 week. Rod- and oval-shaped cells were detected in the cultures by phase-contrast microscopy. Some of the cells formed long chains. |
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