The explanation is connected with mechanism of metal ability to enter to bacteria (Lebrun et al., 1994) and with different MT affinity to metals (Toriumi et al., 2005). Lebrun et al. studied Listeria monocytogenes, which is similar to S. aureus. L. monocytogenes has cadmium resistance gene (pLm74) and this gene is like plasmid pI258 inS. aureus and prevents accumulation of Cd2+in the bacteria byan ATPase efflux mechanism. Results showed cadmium-inducible synthesis of L. monocytogenes cadAC RNA (Lebrun et al., 1994).Moreover, the relationship between metallothionein-3 and metalswas observed on the organism E. coli and it was indicated asfollows Cu > Cd > Zn, same as metallothionein-1 and 2. The affin-ity of metallothionein-3 to Cu was much higher compared withother isoforms (Toriumi et al., 2005). According to Silver et al.the MT synthesis is regulated by gene smtB in gram-positivebacteria Enterococcus hirae during metal exposure. In addition to rapid response to toxic metals by growth depression, two long-term mechanisms of increasing smtA MT gene expression was found. After exposure by metal ions three levels of gene regulation can occur (a) by depression of the SmtB repressor, (b)by amplification of the gene, and (c) by deletion of the repres-sor gene between fixed chromosomal points (Silver and Phung,1996).
The explanation is connected with mechanism of metal ability to enter to bacteria (Lebrun et al., 1994) and with different MT affinity to metals (Toriumi et al., 2005). Lebrun et al. studied Listeria monocytogenes, which is similar to S. aureus. L. monocytogenes has cadmium resistance gene (pLm74) and this gene is like plasmid pI258 inS. aureus and prevents accumulation of Cd2+in the bacteria byan ATPase efflux mechanism. Results showed cadmium-inducible synthesis of L. monocytogenes cadAC RNA (Lebrun et al., 1994).Moreover, the relationship between metallothionein-3 and metalswas observed on the organism E. coli and it was indicated asfollows Cu > Cd > Zn, same as metallothionein-1 and 2. The affin-ity of metallothionein-3 to Cu was much higher compared withother isoforms (Toriumi et al., 2005). According to Silver et al.the MT synthesis is regulated by gene smtB in gram-positivebacteria Enterococcus hirae during metal exposure. In addition to rapid response to toxic metals by growth depression, two long-term mechanisms of increasing smtA MT gene expression was found. After exposure by metal ions three levels of gene regulation can occur (a) by depression of the SmtB repressor, (b)by amplification of the gene, and (c) by deletion of the repres-sor gene between fixed chromosomal points (Silver and Phung,1996).
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