An operon consisting of a P-type ATPase gene and a transcriptional regulator gene responsible for cadmium resistances in Bacillus vietamensis 151–6 and Bacillus marisflavi 151–25

BACKGROUND: Cadmium (Cd) is a severely toxic heavy metal to most microorganisms. Many bacteria have developed Cd(2+) resistance. RESULTS: In this study, we isolated two different Cd(2+) resistance Bacillus sp. strains, Bacillus vietamensis 151–6 and Bacillus marisflavi 151–25, which could be grown in the presence of Cd(2+) at concentration up to 0.3 mM and 0.8 mM, respectively. According to the genomic sequencing, transcriptome analysis under cadmium stress, and other related experiments, a gene cluster in plasmid p25 was found to be a major contributor to Cd(2+) resistance in B. marisflavi 151–25. The cluster in p25 contained orf4802 and orf4803 which encodes an ATPase transporter and a transcriptional regulator protein, respectively. Although 151–6 has much lower Cd(2+) resistance than 151–25, they contained similar gene cluster, but in different locations. A gene cluster on the chromosome containing orf4111, orf4112 and orf4113, which encodes an ATPase transporter, a cadmium efflux system accessory protein and a cadmium resistance protein, respectively, was found to play a major role on the Cd(2+) resistance for B. vietamensis 151–6. CONCLUSIONS: This work described cadmium resistance mechanisms in newly isolated Bacillus vietamensis 151–6 and Bacillus marisflavi 151–25. Based on homologies to the cad system (CadA-CadC) in Staphylococcus aureus and analysis of transcriptome under Cd(2+) induction, we inferred that the mechanisms of cadmium resistance in B. marisflavi 151–25 was as same as the cad system in S. aureus. Although Bacillus vietamensis 151–6 also had the similar gene cluster to B. marisflavi 151–25 and S. aureus, its transcriptional regulatory mechanism of cadmium resistance was not same. This study explored the cadmium resistance mechanism for B. vietamensis 151–6 and B. marisflavi 151–25 and has expanded our understanding of the biological effects of cadmium.