Microbiological Problems in Strip Mine Areas: Relationship to the Metabolism of Thiobacillus Ferrooxidans

LUNDGREN, DONALD G. Microbiological problems in strip mine areas: Relationship to the metabolism of Thiobacillus ferrooxidans. Ohio J. Sci. 75(6): 280, 1975. The role of the iron oxidizing bacteria in contributing to acid mine drainage is considered relative to the metabolism of the organism. To study acid production an in vitro system was developed using isolated cell envelopes from Thiobacillus ferrooxidans, which retained the ability to oxidize Fe. An oxygen electrode was used to follow oxygen depletion as Fe was oxidized. The kinetics of Fe oxidization was analyzed over a temperature range of 15° to 60° C and temperature effects were plotted as Arrhenius plots and Km's and Vmax's were determined at different temperatures. Activation energies of 4.5 kcal/mole for cytochrome oxidase and 11.4 kcal/ mole for cytochrome c reductase were noted for the two enzymes involved in Fe oxidation. The relative binding affinity of Fe (Km) was relatively stable to temperature changes but reaction rates (Vmax) did increase as expected. The power of the microbe is a continuously misunderstood phenomenon in sanitary biology. Because microbes are inconspicuous, they are often overlooked as agents of environmental problems. As a general microbiologist, I have always accepted a doctrine advanced by microbial scholars—never underestimate the power of the microbe. Also, I have learned that within the field of microbial ecology the concept of chemoautotrophy is extremely vital to one's understanding iManuscript received January 10, 1975. Presented as part of a symposium, Biological Implications of Strip Mining, held at Battelle Memorial Institute, Columbus, Ohio, on November 15, 1974. of how the microbe contributes to the movements of the earth and the various elemental cycles of nature. This concept should not be strange to this audience, for within this concept lies an understanding of the biological problems we are discussing during the symposium. Chemoautotrophic bacteria are those that obtain their energy necessary for growth and carbon assimilation from the oxidation of reduced sulfur, and iron compounds, iron metals, ammonium ion, nitrite ion and hydrogen. The bulk of their carbon for existence comes from CO2 assimilation. Of immediate attention and interest to this group are the iron and sulfur oxidizing bacteria which are very much concerned with acid mine drainage, the mining of copper and uranium and the displacements of large buildings. Time does not permit discussion of the latter two problems, but they are becoming more and more important as man is faced with energy depletion and construction needs. To focus upon our immediate problem of acid mine drainage and the bacterium Thiobacillus ferrooxidans, a fundamental reference to Singer and Stumm (1970) is important. These authors relate the following conditions: (+O2) (1) FeS2 >Fe ++S—compounds (2) bacterium >Fe++O2 catalyst