부산대학교 도서관

The potential for humic substances to serve asterminal electron aceptors in microbial respiration and theeffects of humic substances on microbial azoreduction wereShewanella decolorationis S12 was able to conserve energyto support growth from electron transport to humics coupledto the oxidation of various organic substances or H2. Batchexperiments suggested that when the concentration ofanthraquinone-2-sulfonate (AQS), a humics analog, was lowerthan 3 mol/l, azoreduction of strain S12 was acceleratedunder anaerobic condition. However, there was obvious inhibitionto azoreduction when the concentration of the AQS was2-sulfonate (AQDS), could stil prominently accelerateazoreduction, even when the concentration was up to 12 mol/l,but the rate of acceleration gradually decreased with the increasingconcentration of the AQDS. Toxic experiments revealed thatAQS can inhibit growth of strain S12 if the concentration pasta critical one, but AQDS had no effect on the metabolism andgrowth of strain S12 although the concentration was up to20 mol/l. These results demonstrated that a low concentrationof humic substances not only could serve as the terminal electronas redox mediator shuttling electrons for the anaerobicazoreduction by S. decolorationis S12. However, a highconcentration of humic substances could inhibit the bacterialazoreduction, resulting on the one hand from the toxic effecton cell metabolism and growth, and on the other hand fromcompetion with azo dyes for electrons as electron acceptor.