The enrichment and isolation in pure culture of a bacterium, identified as a strain of Desulfovibrio, able to release and reduce the sulfur of isethionate (2-hydroxyethanesulfonate) and other sulfonates to support anaerobic respiratory growth, is described. The sulfonate moiety was the source of sulfur that served as the terminal electron acceptor, while the carbon skeleton of isethionate functioned as an accessory electron donor for the reduction of sulfite. Cysteate (alanine-3-sulfonate) and sulfoacetaldehyde (acetaldehyde-2-sulfonate) could also be used for anaerobic respiration, but many other sulfonates could not. A survey of known sulfate-reducing bacteria revealed that some, but not all, strains tested could utilize the sulfur of some sulfonates as terminal electron acceptor. Isethionate-grown cells of Desulfovibrio strain IC1 reduced sulfonate-sulfur in preference to that of sulfate; however, sulfate-grown cells reduced sulfate-sulfur in preference to that of sulfonate.

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A variety of sulphonates were tested for their ability to serve as nutrients for Escherichia coli, Enterobacter aerogenes and Serratia marcescens. Cysteate, taurine and isethionate could not serve as sole sources of carbon and energy but, under aerobic conditions, could be utilized as sources of sulphur. Both sulphate and sulphonate supported equivalent cell yields, but the generation times varied with the sulphonate being metabolized. The sulphonate-S of HEPES buffer, dodecane sulphonate and methane sulphonate was also utilized by some strains, whereas the sulphonate-S of taurocholate was not. None of the sulphonates tested served as a sulphur source for growth under anaerobic conditions. Sulphonate utilization appears to be a constitutive trait ; surprisingly, however, cells of E. coli and Ent. aerogenes utilized sulphate-S in preference to that of sulphonate, when both were present. E. coli mutants unable to use sulphate as a source of sulphur because of deficiencies in sulphate permease, ATP sulphurylase, adenylylsulphate kinase (APS kinase) or glutaredoxin and thioredoxin were able to utilize sulphonates ; hence sulphate is not an obligatory intermediate in sulphonate utilization. However, mutants deficient in sulphite reductase were unable to utilize sulphonates ; therefore, this enzyme must be involved in sulphonate utilization, though it is not yet known whether it acts upon the sulphonates themselves or upon the inorganic sulphite derived from them.

Bacterial assimilation of sulfonate‐sulfur under anaerobic conditions has been demonstrated. Two different bacteria able to grow fermentatively using sulfonate‐sulfur as sole sulfur source were isolated by enrichment culture; neither were able to utilize sulfonates as sole source of carbon and energy for growth. The isolate of Clostridium pasteurianum assimilated the sulfur of isethionate (2‐hydroxyethanesulfonate), taurine (2‐aminoethanesulfonate), or p‐toluenesulfonate. A facultatively fermentative Klebsiella strain did not utilize the sulfur of any of these sulfonates, but assimilated cysteate‐sulfur; in contrast, when growing by aerobic respiration, the range of sulfonates able to serve as sulfur source was greater. Both bacteria displayed a preferential utilization of sulfate‐sulfur to that of the sulfonates tested. Thus, bacterial assimilation of sulfonate‐sulfur during anaerobic growth has direct parallels with features until now recognized only for aerobic assimilatory processes.

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