Four rock samples were collected as soon as the core liners were split at Site 1163 to characterize the microbial community inhabiting this environment (Table T2). One breccia fragment (Sample 187-1163A-8R-1 [Piece 4, 33-35 cm]), two pillow basalt fragments composed of partially altered glass rinds and crystalline basalt (Samples 187-1163A-2R-1 [Piece 5, 27-29 cm] and 4R-1 [Piece 9, 50-52 cm]), and one fragment of crystalline basalt (Sample 187-1163B-10R-1 [Piece 5, 62-65 cm]) (see "Igneous Petrology") were sampled. To sterilize them, the outer surfaces of the rocks were quickly flamed with an acetylene torch, and 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 one core to evaluate the extent of contamination caused by drilling fluid (see "Tracer Test" in "Microbiology" in the "Explanatory Notes" chapter and Table T2). Pieces of rock were rinsed in nanopure water, and the water was then filtered. Thin sections were examined to determine 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 the filter. 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. Nineteen microspheres were observed in thin sections from Core 187-1163A-2R.