RESUMO
AIMS: To isolate thiodiglycol (TDG)-degrading bacteria, the mustard gas hydrolysis product, and to characterize the metabolites formed and the enzymes involved in the degradation. METHODS AND RESULTS: Two strains, identified as Achromobacter xylosoxydans G5 and Paracoccus denitrificans E4, isolated from a petroleum-contaminated soil, utilized TDG as sole carbon and sulfur source. During the degradation of TDG by strain E4 [(2-hydroxyethyl)thio] acetic acid (HETA), thiodiglycolic acid (TDGA) and bis-(2-hydroxyethyl)disulfide (BHEDS) were identified by gas chromatography-mass spectrometry analysis, while HETA and TDGA were identified for strain G5. Two-dimensional isoelectric focussing-gel electrophoresis (2-D IEF/SDS-PAGE) maps of protein extracts of P. denitrificans E4 grown on TDG showed a spot identified as a methanol dehydrogenase. Increased expression of a putative iscS gene, involved in sulfur assimilation, was observed in TDG-grown cells of A. xylosoxydans G5. CONCLUSIONS: TDG degradation by P. denitrificans E4 occurred through two pathways: one involved cleavage of the C-S bond of HETA, yielding BHEDS and the other, oxidation of the alcoholic groups of TDG, yielding TDGA. The cleavage of the C-S bond of TDGA gave mercaptoacetic acid, further oxidized to acetate and sulfate. SIGNIFICANCE AND IMPACT OF THE STUDY: Increased knowledge of TDG-degrading bacteria and the possibility of using them in a tailored-two-stage mustard gas destruction process.