Sulfonate-sulfur can be assimilated for fermentative growth

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.