抄録
The population dynamics and acetate utilization kinetics of two strains of phototrophic purple nonsulfur (PPNS) bacteria, Rhodopseudomonas sp. strain TUT3630 and Rhodobacter sp. strain TUT3733, in a continuous co-culture system were investigated. The mixed populations were cultured stepwise at different concentrations of acetate under semi-aerobic conditions in the light and were monitored by 16S rRNA-targeted fluorescence in situ hybridization (FISH) and PCR-denaturing gradient gel electrophoresis (DGGE). Cells of Rhodobacter sp. strain TUT3733, having a low affinity for acetate, dominated when the acetate concentration in the feed ranged from 5 to 20 mM. On the other hand, the feeding of less than 1 mM of acetate resulted in an increase in cell numbers of Rhodopseudomonas sp. strain TUT3630 due to its high affinity for acetate. These results suggest that the affinity for acetate is one of the most important determinants for the competitiveness among different species of PPNS bacteria in the environment. Our results provide a plausible explanation for why Rhodobacter species proliferate as the major PPNS bacteria in wastewater environments containing high levels of lower fatty acids, and the reverse is the case in Rhodopseudomonas species.
