At Site 1271, one rock interval, Sample 209-1271B-7R-1 (Piece 6, 32–48 cm), was collected to characterize the microbial community inhabiting this environment. The rock sample is a completely serpentinized dunite.
The sample was prepared as described in "Igneous Rocks" in "Microbiology" in the "Explanatory Notes" chapter. The type and extent of contamination caused by drill fluids was evaluated as described in "Contamination Tests" in "Microbiology" in the "Explanatory Notes" chapter. The results for the perfluorocarbon tracer (PFT) showed that the PFT reached the exterior of the core and may have penetrated to the interior of the microbiology sample (Table T11; Fig. F74). A sample from Section 209-1271A-7R-1 (Piece 6) was rinsed in nanopure water, and the collected water (38 mL) was filtered and examined under a fluorescence microscope. Microsphere concentration was 9.43 x 105 microspheres/mL of wash. A 0.5-g interior piece of the sample was examined under a fluorescence microscope to detect microsphere penetration. The results showed that the microspheres did not penetrate to the interior of the sample.
Aliquots of surface water were collected and prepared for deoxyribonucleic acid (DNA) analysis as described in "Seawater and Water Samples" in "Microbiology" in the "Explanatory Notes" chapter.
A mud sample was collected from Hole 1271A for microbial analysis. The sample was from sediment entrained in the core barrel during a push-in test to determine sediment thickness. Microscopic observation showed that the sample was reddish brown and composed of nannofossils and fine inorganic particles. Since no mudline was established, no curation sample designation was assigned other than hole number. A total of 20 g of mud and 10 mL of sterile artificial seawater (ASW) was placed in a sterile 50-mL tube for analysis. The sample was then mixed by shaking until the sediment was dispersed in the fluid. Direct counts and cultures of the samples were prepared as described in "Direct Counts and Enrichment Cultures" in "Sediments" in "Microbiology" in the "Explanatory Notes" chapter. Results of direct count assay were 1.89 x 106 bacteria/mL and 8.49 x 106 viruses/mL. A 10-µL aliquot from the sample (no clearing allowed) was added to 900 µL of ASW and filtered through a 45-µm nitrocellulose membrane filter and placed on a nutrient agar plate. Growth (colonies were too numerous to count) was noted on the filter surface and on particulates at the filter surface after 24 hr of incubation at room temperature (~23.0°C). Both the direct count data and the culture data indicate that bacteria were in interstitial spaces and attached to sediment particles. The remaining sample was stored at –70°C for shore-based DNA analysis of the microbial community.