Kinetics of a chlorate-accumulating, perchlorate-reducing bacterium

Kinetics parameters for perchlorate and chlorate reduction were determined for Dechlorosoma sp. HCAP-C, also known as Dechlorosoma sp. PCC, a novel perchlorate-reducing bacterium (PCRB) that accumulates significant amounts of chlorate during perchlorate reduction. This is the first report of such behavior, and we hypothesized the perchlorate reduction kinetics would be markedly different from other PCRB. In batch tests with initial perchlorate concentrations ranging from 200 to around 1400 mg/L, maximum chlorate accumulation ranged from 41 to 279 mg/L, and were consistently around 20% of the initial perchlorate concentration. For perchlorate, parameters were determined using a competitive inhibition model. The maximum specific substrate degradation rate qmax P was 11.5 mg ClO4−/mg dry weight (DW)-d, and the half-maximum rate constant KP was 193 mg ClO4−/L. For chlorate, the qmax C was 8.3 mg ClO3−/mg DW-d and the KC was 58.3 mg ClO3−/L. The high KP values relative to conventional PCRB, values suggests that HCAP-C does not play a significant role at low perchlorate concentrations. However, the relatively high qmax P, and the potential for syntrophic relationships with chlorate-reducing bacteria that relieve the effects of chlorate inhibition, suggest that HCAP-C could play a significant role at high perchlorate concentrations.