Kinetics of a hydrogen-oxidizing, perchlorate-reducing bacterium

Abstract: This paper provides the first kinetic parameters for a hydrogen-oxidizing perchlorate-reducing bacterium (PCRB), Dechloromonas sp. PC1. The q max for perchlorate and chlorate were 3.1 and 6.3mg/mgDW-day, respectively. The K for perchlorate was 0.14mg/L, an order of magnitude lower than reported for other PCRB. The yields Y on perchlorate and chlorate were 0.23 and 0.22mgDW/mg, respectively, and the decay constant b was 0.055/day. The growth-threshold, S min, for perchlorate was 14μg/L, suggesting that perchlorate cannot be reduced below this level when perchlorate is the primary electron-acceptor, although it may be possible when oxygen or nitrate is the primary acceptor. Chlorate accumulated at maximum concentrations of 0.6–4.3mg/L in batch tests with initial perchlorate concentrations ranging from 100 to 600mg/L. Furthermore, 50mg/L chlorate inhibited perchlorate reduction with perchlorate at 100mg/L. This is the first report of chlorate accumulation and inhibition for a pure culture of PCRB. These Chlorate effects are consistent with competitive inhibition between perchlorate and chlorate for the (per)chlorate reductase enzyme. [Copyright &y& Elsevier]