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USING RESPIROMETRY TO MEASURE HYDROGEN UTILIZATION IN SULFATE REDUCING BACTERIA IN THE PRESENCE OF COPPER AND ZINC
Citation:
Holder, E., M. J. Kupferle, H H. Tabak, AND J R. Haines*. USING RESPIROMETRY TO MEASURE HYDROGEN UTILIZATION IN SULFATE REDUCING BACTERIA IN THE PRESENCE OF COPPER AND ZINC. Presented at The 19th Annual International Conference on Contaminated Soils, Sediments, and Water, University of Massachusetts, Amherst, MA, 10/20-23/2003.
Description:
A respirometric method has been developed to measure hydrogen utilization by sulfate reducing bacteria (SRB). One application of this method has been to test inhibitory metals effects on the SRB culture used in a novel acid mine drainage treatment technology. As a control parameter for that technology, it is necessary to know the metal concentration that has either an inhibitory or toxic effect on the bacteria both alone and in the acid mine waste matrix.
An enrichment culture of SRB was developed that is mixotrophic, utilizing carbon dioxide (CO2) and acetate as the carbon sources and hydrogen (H2) as the electron donor for the conversion of sulfate to hydrogen sulfide (H2S). Respirometers (NCON Systems Inc.) were adapted to measure H2 uptake. Hydrogen uptake by SRB is similar to the uptake of oxygen in aerobic cultures in that it causes the production of another gas, H2S in the former case and CO2 in the latter. Produced biogenic H2S is removed with a zinc acetate trap, analogous to an alkaline trap for CO2 in aerobic respirometry. In the case of H2 respirometry, CO2 is retained in the headspace. Respirometry can differentiate between either a toxic effect (suppression of hydrogen uptake) or an inhibitory effect (evidenced by an increased lag time relative to a control.)
Metal complexation can be a problem in testing inhibition effects because most bacteriological media contain components which can form metal complexes, thereby reducing the metal bioavailability. The culture media formulated by Sani et al. (Advances in Environmental Research 5 (2001) 269-276) was modified for use with this culture. Metal complexation was reduced by replacing orthophosphate with tryptone and PIPES for pH control.
Respirometric data; metal, sulfate, and sulfide concentrations; and biomass measurements show that soluble zinc has an inhibitory effect between 10 and 25 ppm and soluble copper is inhibitory between 1 and 17 ppm. The toxic level for zinc is 50 ppm and for copper is 27 ppm.