BIODEGRADATION OF SULFOSUCCINATE - DIRECT DESULFONATION OF A SECONDARY SULFONATE

The bacterial biodegradation of a secondary sulphonate, sulphosuccinat e, has been shown to occur by direct desulphonation. A bacterium, desi gnated Pseudomonas sp. BS1, was isolated from activated sewage sludge, for its capacity to grow on sulphosuccinate as the sole source of car bon and energy. Cultures grown on sulphosuccinate were able to convert this substrate to sulphite which was subsequently oxidized rapidly to sulphate. The sequence of desulphonation and carbon-chain catabolism of sulphosuccinate was determined from measurements of the kinetics of sulphite and (CO2)-C-14 release from specifically radiolabelled sulph o[1,4-C-14]succinate and sulpho[2,3-C-14]succinate, which were synthes ized from the corresponding maleic anhydrides. When each radiolabelled compound was incubated separately with washed-cell suspensions of Pse udomonas BS1, sulphite was released before (CO2)-C-14, as shown by che mical assay and radiorespirometry, respectively. Differences in the ki netics and extent of (CO2)-C-14 release from the 1,4- and 2,3-labelled substrates were consistent with entry of the intact C-4 chain into th e citric acid cycle. When carrier oxaloacetate was added to incubation mixtures containing resting-cell suspensions and radiolabelled sulpho succinate, a radiolabelled metabolite with the same HPLC retention tim e as oxaloacetate accumulated. No radioactive metabolites accumulated when carrier oxaloacetate was replaced with succinate, fumarate or mal ate. Collectively, the data indicated co-production of sulphite and ox aloacetate from sulphosuccinate, which is interpreted in terms of an o xidative desulphonation mechanism.