Microbial Ecology of Perchlorate-Reducing Bacteria that Accumulate High Levels of Chlorate

Perchlorate (ClO4-) is a harmful oxidant found in drinking water sources throughout the US. Recently, several strains of perchlorate-reducing bacteria (PCRB) that accumulate large amounts of chlorate during perchlorate reduction have been isolated and studied. In this study, it was estimated that these novel perchlorate reducers have similar qmax values to conventional PCRB (8.3mgClO3-/mgX-day and 11.5mgClO4-/mgX-day) and much higher K values (58.3mg/L for chlorate and 192.6mg/L for perchlorate). Based on these kinetic parameters, these novel perchlorate reducers are unlikely to play a significant role in perchlorate reduction at concentrations below 200 mg/L, but may contribute to faster degradation at high concentrations. Analysis of the nucleotide and amino acid sequences of the catalytic subunit of the (per)chlorate reductase enzyme (pcrA) of three high chlorate accumulating isolates were highly similar and distinct from conventional PCRB, suggesting that structural differences in the pcrA enzyme could account for differences in microbial activity.