Abstract
Cysteine auxotrophs of S. typhimurium mutated in cysB, cysI or cysJ grew with sulfate as a sulfur source when incubated under a H2/CO2 atmosphere. Yields obtained under these conditions were equivalent to those characteristic of wild-type S. typhimurium. The same mutants failed to grow with sulfate as a S source when incubated aerobically. Auxotrophs mutated in cysA, cysC, cysD, cysE, cysG and cysH required cysteine for growth under both incubation conditions. The results suggest that mutations in cysB (regulation of the several cys operons) and also cysI and cysJ (sulfite reductase activity) can be circumvented during anaerobic growth under H2.