Full text loading...
Abstract
SUMMARY: Inhibition of autotrophic ammonia and nitrite oxidation by potassium ethyl xanthate (PEX) was studied in ammonium- and nitrite-limited chemostat cultures of Nitrosomonas europaea and Nitrobacter, respectively. Ammonia and nitrite oxidation were both stimulated by addition of low concentrations of PEX (0·1 μg ml-1), which significantly decreased steady-state substrate concentrations and increased steady-state cell concentrations. Addition of similar concentrations to exponentially growing cultures resulted in a slight stimulation of growth of Nitrobacter but did not affect Nitrosomonas. Inhibition of ammonia and nitrite oxidation by higher concentrations of PEX resulted in establishment of steady states without induction of lag phases, observed in batch culture, which would have resulted in wash-out. Establishment of steady states occurred more quickly and with less variation in substrate concentrations following addition of inhibitory rather than stimulatory concentrations of PEX. Steady-state data indicate that PEX may act as a competitive inhibitor of nitrite oxidation by Nitrobacter.
- Received:
- Revised:
- Published Online: