Enrichment cultures with enantiomeric 2-(4-sulfophenyl)butyrate (SPB) as the sole added source(s) of carbon and energy for growth yielded a pure culture of a degradative bacterium, which was identified as Delftia acidovorans SPB1. The organism utilized the enantiomers sequentially. R-SPB was utilized first (specific growth rate [] ‫؍‬ 0.28 h ؊1 ), with transient excretion of an unknown intermediate, which was identified as 4-sulfocatechol (4SC). Utilization of S-SPB was slower ( ‫؍‬ 0.016 h ؊1 ) and was initiated only after the first enantiomer was exhausted. Suspensions of cells grown in S-SPB excreted 4SC, so metabolism of the two enantiomers converged at 4SC. The latter was degraded by ortho cleavage via 3-sulfo-cis,cis-muconate. Strain SPB1 grew with 4SC and with 1-(4-sulfophenyl)octane (referred to herein as model LAS) but not with commercial linear alkylbenzenesulfonate (LAS) surfactant, which is subterminally substituted but nontoxic. It would appear that metabolism of the model LAS does not represent metabolism of commercial LAS.One of the major xenobiotic compounds degraded in sewage works worldwide is linear alkylbenzenesulfonate (LAS) surfactant, which has an annual production of about 2,500,000 tons (40). Whereas the degradation of LAS is well established (16,26,27,35,39,43), the mechanisms of its degradation are not (4).Commercial LAS (Fig. 1) is, ideally, a mixture of linear alkanes (C 10 to C 13 ) subterminally substituted with a single 4-sulfophenyl moiety (31): this means a mixture of 20 compounds, 18 of which are racemic mixtures. Although many different degradative reactions have been deduced from the intermediates which have been observed (38,43), the general opinion is that the major degradative pathway involves oxygenation of one or both of the terminal methyl groups by an unknown oxygenase (see also references 19 and 20) followed by rounds of ␤-oxidation to yield a large set of transient sulfophenyl(di)carboxylates ( Fig. 1) (9,14,17,38,43,47,49). On paper, seven sulfophenyl(di)carboxylates, representing a maximum number of ␤-oxidation steps, can be proposed: 2-(4-sulfophenyl)butyrate (SPB) (which is often observed during the degradation of commercial LAS [e.g., see reference 14]), 2-(4-sulfophenyl)propionate, 2-(4-sulfophenyl)malonate, 3-(4-sulfophenyl)butyrate, 2-(4-sulfophenyl)succinate, 3-(4-sulfophenyl)valerate and 3-(4-sulfophenyl)glutarate.Many of these sulfophenyl(di)carboxylates are optically active (24), which can be assumed to have consequences for their further degradation (25,50). SPB is quantitatively converted to cell material, CO 2 , water, and sulfate by activated sludge (27), but none of the degradative mechanisms are known (4).We now describe the isolation of Delftia acidovorans SPB1, which degrades both enantiomers of SPB via 4-sulfocatechol (4SC) and ortho ring cleavage (7, 13). MATERIALS AND METHODSMaterials. Racemic, R-and S-SPB were synthesized by reacting sulfuric acid with the corresponding phenylcarboxylic acid (45). Yields of about 30% were obtained at about 97%...

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