Three rock samples (187-1164B-3R-1 [Piece 11, 79-82 cm], 8R-1 [Piece 7, 28-31 cm], and 10R-1 [Piece 1, 0-4 cm]) were collected from Hole 1164B to characterize the microbial community inhabiting this environment (Table T3). All samples were pillow basalt fragments, composed of partially altered glass rinds and more crystalline interiors (see "Igneous Petrology"). Section 187-1164B-3R-1 (Piece 11) had sediment attached to a chilled margin. 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 on one basement core from Hole 1164A and two from Hole 1164B to evaluate the extent of contamination caused by drilling fluid (see "Tracer Test" in "Microbiology" in the "Explanatory Notes" chapter and Table T3). Pieces of rock from each core were rinsed in nanopure water, and the collected water was filtered. No thin section was made from Core 187-1164A-2R because only one piece of rock was recovered. Thin sections from Hole 1164B cores 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 may have been relocated by polishing. Thirty-six microspheres were observed in the thin section from Core 187-1164B-2R and 14 from Core 187-1164B-10R.