An operon consisting of a P-type ATPase gene and a transcriptional regular gene given the different cadmium resistances in Bacillus vietamensis 151-6 and Bacillus marisflavi 151-25

Cadmium (Cd) is a severely toxic heavy metal to most microorganisms. Many bacteria have developed Cd2+ resistance. In this study, we isolated two different Cd2+ resistance Bacillus sp. strains, Bacillus vietamensis 151-6 and Bacillus marisflavi 151-25, which could be grown in the presence of Cd2+ at concentration up to 0.3 mM and 0.8 mM, respectively. According to the genomic sequencing, transcriptome under cadmium stress and related biological experiments, a gene cluster in plasmid p25 containing orf4802 and orf4803, which encode an ATPase transporter and a transcriptional regulator protein, respectively, was a major contributor to Cd2+ resistance in B. marisflavi 151-25. Although 151-6 has much lower Cd2+ resistance than 151-25, they contain similar gene cluster, but in different locations. A gene cluster on the chromosome containing orf4111, orf4112 and orf4113, which encode an ATPase transporter, a cadmium efflux system accessory protein and a cadmium resistance protein, respectively, was found to be a major role on the Cd2+ resistance for B. vietamensis 151-6. Based on homologies to the cad system (CadA-CadC) in Staphylococcus aureus, the mechanisms of cadmium resistance in B. vietamensis 151-6 and B. marisflavi 151-25 were as same as the cad system. Our study on the cadmium mechanism for B. vietamensis 151-6 and B. marisflavi 151-25 proved preliminarily that the cad system is widespread in Bacillus sp. bacteria.