The role of integrative conjugative elements (ICE) in the realization of Vibrio cholerae resistance to heavy metals

The aim of the work was to identify possible genes responsible for resistance to heavy metals in toxigenic vibrio cholerae. Two strains of V. cholerae O1 – 83 and 5879 and E. coli QD5003 Rif r were used in the work. A sample of complete genomes of toxigenic vibrio cholerae for in silico analysis was presented with 1,880 strains of various serogroups and release dates. A comparative bioinformatics analysis by subtracting genomes in strain V. cholerae 83 revealed a gene identified as czcA based on GenBank data (sequence MVB73536.1). When analyzing the sequenced genomes of 1,880 V. cholerae strains of various serogroups and release dates, czcA was detected in 159 toxic V. cholerae strains out of 1,125 studied (14.1%), but not in one of the 775 genomes of non-toxic vibrios. By performing PCR with virtual primers in silico, the czcA gene was identified in strain V. cholerae 83 as part of an integrative conjugative element of the ICEVchBan11 type. Two types of integrative conjugative elements were reliably identified among 159 czcA+ genomes of V. cholerae: 113 ICEVchBan9 and 27 ICEVchBan11. To analyze the possible biological role of czcA, conjugative transfer of ICEVchBan11 into V. cholerae 5879 cells was performed, while czcA+ cells of strain 5879 significantly increased resistance to cadmium ions. The data obtained may indicate the biological feasibility of the presence of the czcA gene in toxigenic vibrio cholerae as a factor in increasing resistance to the toxic effects of heavy metals, in particular cadmium, in case of possible ingestion into reservoirs with a high content of its ions.