Alcaligenes xylosoxydans subsp. denitrificans TD1, possessing degrading activity against thiodiglycol (TDG), was isolated from soil samples contaminated by the products of mustard detoxification. Using long-term selection, the most active strain A. xylosoxydans TD2 was obtained. The effect of cultivation conditions-pH, specific substrate loading (SSL) and substrate concentration on the efficiency of TDG destruction process were determined. The initial microbial attack on the TDG molecule involved oxidation of both sulphur atom and primary alcohol groups with the formation of diglycolsulphoxide (DGSO) and thiodiglycolic acid (TDGA), respectively. The transformation to DGSO is a catabolic deadlock since this compound is not oxidized by bacterial cells or used by them as a sole carbon source for growth. The key metabolic reaction of TDG degradation is the of SO42- uncoupling of the C-S bond of intermediates-TDGA and thioglycolic acid (TGA). This reaction leads to the formation 4 ions and acetate, which is involved in the reactions of central metabolic pathways. A scheme for TDG metabolism by A. xylosoxydans TD2 was suggested. (C) 2002 Elsevier Science Ltd. All rights reserved.