TETRACHLOROETHENE METABOLISM OF DEHALOSPIRILLUM MULTIVORANS

Dehalospirillum multivorans is a strictly anaerobic bacterium that is able to dechlorinate tetrachloroethene (perchloroethylene; PCE) via tr ichloroethene (TCE) to cis-1,2-dichloroethene (DCE) as part of its ene rgy metabolism. The present communication describes some features of t he dechlorination reaction in growing cultures, cell suspensions, and cell extracts of D. multivorans. Cell suspensions catalyzed the reduct ive dechlorination of PCE with pyruvate as electron donor at specific rates of up to 150 nmol (chloride released) min(-1) (mg cell protein)( -1) (300 mu M PCE initially, pH 7.5, 25 degrees C). The rate of dechlo rination depended on the PCE concentration; concentrations higher than 300 mu M inhibited dehalogenation. The temperature optimum was betwee n 25 and 30 degrees C; the pH optimum at about 7.5. Dehalogenation was sensitive to potential alternative electron accepters such as fumarat e or sulfur; nitrate or sulfate had no significant effect on PCE reduc tion. Propyl iodide (50 mu M) almost completely inhibited the dehaloge nation of PCE in cell suspensions. Cell extracts mediated the dehaloge nation of PCE and of TCE with reduced methyl viologen as the electron donor at specific rates of up to 0.5 mu mol (chloride released) min(-1 ) (mg protein).(-1) An abiotic reductive de halogenation could be excl uded since cell extracts heated for 10 min at 95 degrees C were inacti ve. The PCE dehalogenase was recovered in the soluble cell fraction af ter ultracentrifugation. The enzyme was not inactivated by oxygen.