Functional analysis of the Bacillus subtilis cysK and cysJI genes

The function of the Bacillus subtilis cysk and cysJI (previously designated yvgQR) genes, expected to be involved in the assimilatory sulfate reductio n pathway, was investigated. A B. subtilis mutant with a deletion in the cy sJI genes was unable to use sulfate or sulfite as sulfur source, which conf irmed that these genes encode sulfite reductase. A mutant with a transposon insertion in the cysK gene, whose deduced protein sequence showed similari ty to cysteine syntheses, grew poorly on sulfate and butanesulfonate. A str ain in which cysK and yrhA, a cysK paralog, were inactivated was unable to grow with sulfate. Whereas expression of the cysJI genes was induced by sul fate, expression of cysK was repressed both by sulfate and by cysteine. (C) 2001 Federation of European Microbiological Societies. Published by Elsevi er Science B.V. All rights reserved.