Desulfonation by diverse physiological types of bacteria

Date of Completion

January 2003

Keywords

Biology, Microbiology

Degree

Ph.D.

Abstract

The ability of a sulfonate to serve as an electron donor during phototrophic bacterial growth has been demonstrated. Purple nonsulfur bacteria were isolated by enrichment culture on 2-aminoethanesulfonate (taurine) as a sole electron donor, sulfur and nitrogen source. Two organisms were identified as Rhodopseudomonas palustris strain Tau1 and Rhodobacter sphaeroides strain Tau3 and differed from their ATCC type strains in their ability to use taurine as an electron donor. R. palustris Tau1 grew photoautotrophically deriving all of its carbon from CO2, while R. sphaeroides Tau3 grew photoheterotrophically assimilated taurine-carbon and CO2. Inducible deaminating/desulfonating enzymes were detected in both of the enrichment culture isolates when grown on taurine or its carboxyl analog β-alanine. Other purple nonsulfur bacteria enrichment isolates and type ATCC strains were examined for ability to desulfonate various natural and xenobiotic alkyl-, arylsulfonates. Only enrichment isolates of purple nonsulfur bacteria were capable of assimilating alkyl sulfanate-sulfur. The ATCC strain of R. pahistris was able to assimilate 3-,4-sulfobenzoate-sulfur, while an enrichment isolate was also able to utilize 3-, 4-sulfobenzoate as a sole electron donor, and carbon. ^ The enzymology of a range of taurine-grown cells of both anaerobic and aerobic organisms was examined. Clostridium pasteurianum strain Cl assimilating taurine-sulfur could not desulfonate taurine with out prior deamination. Rhodococcus spp. growing on taurine as a sole carbon, nitrogen and sulfur source showed the presence of an inducible nonspecific aminotransferase in cell extracts. This activity was induced by taurine or its carboxyl analog β-alanine, not the absence of sulfate (in contrast to aerobic sulfonate-sulfur assimilation). This activity differed from the taurine-specific aminotransferases induced in the anaerobes, Desulforhopahis singaporensis and C. pasteurianum C1. A phylogenetic analysis of “taurine” aminotransferases in the protein data base suggests a split between aerobic and anaerobic organisms coinciding with a nonspecific ω-amino acid:pyruvate or specific taurine:pyruvate aminotransferase respectively. ^ This study enlarges the view of diverse organisms capable of metabolizing sulfonated compounds and suggests that in them similar enzyme systems are used to metabolize particular groups of sulfonate. This has significant implications for the environmental recycling of both natural and xenobiotic sulfonates. ^

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