Characterization of Thiobacillus thioparus isolated from an activated sludge bioreactor used for hydrogen sulfide...

To compare Thiobacillus thioparus population dynamics in a control and a test activated sludge (AS) bioreactor, used for hydrogen sulfide (H(2)S) degradation.

Denaturing gradient gel electrophoresis (DGGE) was used to confirm the presence of T. thioparus, and real-time PCR was used to quantify the level of this bacterium in the AS samples. The DGGE analysis showed a band for T. thioparus in all samples, with the band being more prominent in the test sample with H(2)S diffusion. It also showed that although a change occurred in the diversity of the microbial population in the test sludge after 6 weeks of H(2)S diffusion, the microbial community structure of the test and control was still similar. Thiobacillus thioparus-specific PCR primers confirmed that 50% of the isolates from both the test and control bioreactors were T. thioparus. The thiobacilli population became more efficient at degrading the diffused H(2)S. This increase in efficiency was confirmed by a significant increase in the number of isolates from the test sludge compared with those from the control sludge, when they were grown in a thiosulfate-rich liquid medium.

It was concluded that the use of AS process for H(2)S removal encourages the population of T. thioparus to increase even at times when the total biomass concentration shows a decrease.

The research results give an insight into the dynamics of the microbial population in an AS pilot plant used in a dual role, to treat the wastewater and H(2)S.