At Site 1157, four rock samples were collected to characterize the microbial community inhabiting this environment (Table T2). Breccia fragments (Sample 187-1157A-3R-1 [Piece 20, 120-123 cm]) and pillow basalt fragments, composed of partially altered glass rinds and crystalline basalt (Samples 187-1157B-4R-2 [Piece 10, 68-72 cm] and 187-1157B-8R-1 [Piece 6A, 39-46 cm]), or crystalline basalt only (Sample 187-1157B-2R-1 [Piece 7, 44-47 cm]) were sampled as soon as the core liners were split. To sterilize them, the outer surfaces of the rocks were quickly flamed with an acetylene torch. Enrichment cultures and samples for DNA analysis and electron microscope studies were prepared (see "Igneous Rocks" in "Microbiology" in the "Explanatory Notes" chapter).
Fluorescent microsphere tests were carried out for three rock cores to evaluate the extent of contamination caused by drilling fluid (Table T2) (see "Tracer Test" in "Microbiology" in the "Explanatory Notes" chapter). Pieces of rock from each core were rinsed in nanopure water, and then the water was filtered. Thin sections were used to examine the extent of contamination inside the samples. Filters and thin sections were examined under a fluorescence microscope for the presence of microspheres. Microspheres were detected on all three filters; in the thin sections microspheres were located both inside fractures and on thin-section surfaces. The microspheres on the polished surfaces were always found close to fractures or to thin-section (i.e., piece) margins and may have been relocated by polishing. Sixty microspheres were observed in thin sections from Core 187-1157A-2R, 14 from Core 187-1157B-2R, and 96 from Core 187-1157B-8R.