At Site 1154 three rock samples (Samples 187-1154A-3R-1 [Piece 3A, 11-14 cm], 6R-1 [Piece 10A, 59-62 cm], and 9R-1 [Piece 3A, 11-13 cm]) were collected to characterize the microbial community inhabiting this environment (Table T2). Samples 187-1154A-6R-1 (Piece 10A, 59-62 cm) and 9R-1 (Piece 3A, 11-13 cm) are pillow basalt fragments including both the partly altered glassy margin and the more crystalline interior. Sample 187-1154A-3R-1 (Piece 3A, 11-14 cm) consists only of the crystalline interior of a basalt. To sterilize them, the outer surfaces of the rock samples were quickly flamed with an acetylene torch; enrichment cultures and samples for high-pressure enrichment, DNA analysis, and electron microscope studies were prepared (see "Igneous Rocks" in "Microbiology" in the "Explanatory Notes" chapter).
To evaluate the extent and type of contamination caused by drilling fluid, fluorescent microsphere tests were carried out for the three sampled rock cores (see "Tracer Test" in "Microbiology" in the "Explanatory Notes" chapter and Table T2). One or two pieces from each core were rinsed in nanopure water, and the water was collected for filtration and examined under a fluorescence microscope for the presence of microspheres. Thin sections were used to examine the extent of contamination inside the samples. Microspheres were detected on all three filters and in the thin sections of Samples 187-1154A-3R-1 (Piece 3A, 11-14 cm) and 6R-1 (Piece 10A, 59-62 cm).