CHARACTERIZATION OF THE MICROBIOLOGY WITHIN A 21-M(3) SECTION OF ROCKFROM THE DEEP SUBSURFACE

The distribution of aerobic chemoheterotrophic microorganisms within a 21 m3 section of deep subsurface rock was determined. Nineteen sample s for microbiological analysis were aseptically taken by hand from the walls of a 400 m deep subsurface tunnel after an alpine miner created fresh rock faces 0.76, 1.52, 2.28, and 3.04 m into the tunnel wall. T he direct counts were several orders of magnitude greater than viable counts in all samples. One of each morphologically distinct bacterial type from each sample was purified and analyzed for fatty acid methyl esters (FAME) using the Microbial Identification System (MIDI). Number s of bacterial types, diversity, and equitability of recoverable micro bial communities were the same or similar using either morphotype or F AME analyses as the basis for distinguishing between bacterial types. Twenty-nine genera (Euclidean distance of less-than-or-equal-to 25) we re found within the rock section, while 28 of the 210 bacterial types isolated were nonculturable under the growth regime required for clust er analysis. Most isolates clustered at the genus level with Arthrobac ter, Gordona, and Acinetobacter. Two genera, containing 16 isolates, w ere unmatched to known organisms within the MIDI data base and cluster ed with other isolates at a Euclidean distance greater than 50. While some species (Euclidean distance less-than-or-equal-to 10) were recove red from multiple sites within the rock section, most were found at 1- 3 sites and usually without a definitive pattern of distribution.