Biodegradation of short-chain alkyl sulphates by a coryneform species

Coryneform B1a isolated from soil grew well on butyl-, pentyl- and hexyl-1-sulphates esters and on the corresponding parent alcohols as sole sources of carbon, with growth rates around 0.14–0.19 h^-1. Propyl-1-sulphate and heptyl-1-sulphate supported slower growth, and their C₁, C₂ and C₈ homologues were not utilised at all. Growth of the organism was accompanied by disappearance of butyl-1-sulphate. In the presence of resting cells, butyl-1-sulphate degradation was stoichiometric with the liberation of inorganic sulphate. Butan-1-ol was also detected but in less than stoichiometric amounts. Non-denaturing polyacrylamide gel electrophoresis of extracts of cells grown on butyl-1-sulphate, followed by incubation of gels in butyl-1-sulphate and precipitation of liberated SO₄ ^2- as BaSO₄, revealed a single white band of alkylsulphatase activity. Other zymograms produced in the same way but incubated with the C₅ and C₆ esters, each produced a single band of the same mobility and intensity. With the C₃ and C₇ homologues, the same band was present but considerably less intense. No alkylsulphatase band was detected for methyl, ethyl or octyl-1-sulphates. Assays of alkylsulphatase activity in crude cell-extracts indicated maximum activity towards butyl-1-sulphate at pH 7.5 and 30° C, with K_m=8.4±1.4 mM and V _max =0.13±0.01 mol/min/mg of protein. The results indicated that degradation of short-chain alkyl sulphates in this organism was initiated by enzymic hydrolysis to the corresponding alcohol.     

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 ¹⁸O-label from H₂ ¹⁸O 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[¹⁴C]-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[³⁵S]sulphate showed that release of ³⁵SO₄ ^2- was dependent on availability of O₂, and that there was equimolar stoichiometry among monomethyl sulphate degraded, O₂ consumed and ³⁵SO₄ ^2- released. A proposed pathway for the degradation involved an initial mono-oxygenation to methanediol monosulphate with subsequent elimination of SO₄ ^2- and concomitant formation of formaldehyde. The pathway was compared with degradation mechanisms for other C₁ compounds and for other sulphate esters.