Abstract
This paper describes hydrogen sulfide generation, isolation and characterization of sulfate-reducing bacteria in the activated sludge obtained from wastewater treatment plant. The sludge, collected from aerobic treatment system, was used as inoculums for hydrogen sulfide generation and for isolation of sulfate-reducing bacteria. Hydrogen sulfide was generated when the sludge was inoculated into a pH controlled medium. Two strains G2 and G3 of sulfate-reducing bacteria were isolated from the sludge. The characteristics and identification of these isolates was based on culture of the experiments and molecular analysis. Reduced sulfate rates in G2 and G3 is 0.39 and 0.41 mmol/dm3 respectively. Two isolates located in the genus Desulfovibrio in the phylogenetic tree based. First one was 16S rRNA gene analysis with the highest homology, 96.6 %, as Desulfovibrio carbinoliphilus (DSM 17524T) . However, the branch of the isolates was separated from the relatives and no strain was recognized in this branch. Also the dsr gene of isolate G3 had the highest homology with Desulfovibrio fructosovorans (DSM 3604T) , 92.7 %. The isolates G2 and G3 belonged to the genus Desulfovibrio as confirmed by the results of these analyses, however, these isolates oxidized organic compounds to carbon dioxide completely although relative strain oxidized it completely. Therefore, these isolates have high possibility that they should be recognized as a new strain.
