METAL-TOLERANT BACTERIA IN GEOCHEMICAL-EXPLORATION

Analyses for metal-tolerant bacteria in stream water, using a bioluminescence procedure to measure adenosine triphosphate (ATP) and prepared metal solutions to inhibit bacterial growth, were made on samples from three mineralized areas in Virginia, U.S.A. Two of the areas, Mineral and New Canton, contain massive sulfide deposits believed to be submarine exhalative. The third area (Bowers-Campbell mine) consists of Zn mineralization in carbonate rocks (Mississippi Valley-type). For comparison, the concentration of Zn in minus-80 mesh stream sediments from the same sites was also determined. In addition, several sample sets were also collected from two unmineralized areas near Harrisonburg, Virginia. These sample sets were used for experiments designed to determine the variability due to sampling, the precision of the analytical technique, and the effect that different extraction procedures for ATP and sample storage times have on the analyses. The results indicate the following: (1) the coefficient of variation from an analysis of eight separate water samples (cells per ml) at one location is 15%, sufficient precision for use of the technique in geochemical exploration; (2) larger amounts of ATP are extracted from water samples using boiling TRIS buffer or boiling H2O then EDTA included in a commercial assay kit; (3) the concentration of ATP changes during sample storage; (4) the metal tolerance of bacteria in samples downstream from mineralized areas is much greater then in samples upstream; and (5) each of the three mineralized areas is detected by analyses for metal-tolerant bacteria as well as Zn in minus-80 mesh sediment; however, the geomicrobiological procedure produces much greater anomaly contrasts, both near mineralization and further downstream. There are many potential problems in using geomicrobiological methods in exploration, most of which result from insufficient knowledge about factors which effect the distribution of bacteria in water. This study demonstrated that a simple bioluminescence procedure is practical for use in exploration, and that mineralization in three separate areas with widely differing geochemical characteristics is readily detected using the procedure. Additional studies are needed to see if similar results can generally be obtained. © 1990.