THE ARS OPERON IN THE SKIN ELEMENT OF BACILLUS-SUBTILIS CONFERS RESISTANCE TO ARSENATE AND ARSENITE

The Bacillus subtilis skin element confers resistance to arsenate and arsenite, The ars operon in the skin element contains four genes in th e order arsR, ORF2, arsB, and arsC. Three of these genes are homologou s to the arsR, arsB, and arsC genes from the staphylococcal plasmid pI 258, while no homologs of ORF2 have been found. Inactivation of arsR, arsB, or arsC results in either constitutive expression of ars, an ars enite-and arsenate-sensitive phenotype, or an arsenate-sensitive pheno type, respectively, These results suggest that ArsR, ArsB, and ArsC fu nction as a negative regulator, a membrane-associated protein need for extrusion of arsenite, and arsenate reductase, respectively, Expressi on of the ars operon was induced by arsenate, arsenite, and antimonite , Northern hybridization and primer extension analysis showed that syn thesis of a full-length ars transcript of about 2.4 kb was induced by arsenate and that the ars promoter contains sequences that resemble th e -10 and -35 regions of promoters that are recognized by E sigma(A).