Oxygen-dependent desulphation of monomethyl sulphate by Agrobacterium sp M3C

Agrobacterium sp. M3C, previously isolated from canal-water for its ability to grow on monomethyl sulphate, degraded this ester with stoichiometric liberation of inorganic sulphate. In contrast with the biodegradation of monomethyl sulphate in Hyphomicrobium sp., and of other longer-chain alkyl sulphates in Pseudomonas spp., the pathway in Agrobacterium appeared not to involve a sulphatase enzyme capable of catalysing ester-bond hydrolysis. No such sulphatase was detectable under a range of conditions of bacterial culture, or using various methods for preparing cell-extracts, or different assay conditions. There was no incorporation of O-18-label from (H2O)-O-18 into the liberated inorganic sulphate. No methanol was detectable during biodegradation, and the organism was incapable of growth on methanol, and did not produce methanol dehydrogenase activity when grown on monomethyl sulphate. Tracer studies using mono[C-14]methyl sulphate indicated that formate serine and glycine were produced during the biodegradation. The presence of these amino acids, together with high activity of hydroxypyruvate reductase, indicated the operation of the serine pathway common in methylotrophs. Use of an oxygen electrode in conjunction with monomethyl[S-35]sulphate showed that release of (SO42-)-S-35 was dependent on availability of O-2, and that there was equimolar stoichiometry among monomethyl sulphate degraded, O-2 consumed and (SO42-)-S-35 released. A proposed pathway for the degradation involved an initial mono-oxygenation to methanediol monosulphate with subsequent elimination of SO42- and concomitant formation of formaldehyde. The pathway was compared with degradation mechanisms for other C-1 compounds and for other sulphate esters.