Organomercurial Resistance

Resistance to the toxic effects of mercury is quite commonly found in bacteria (Silver and Walderhaug 1992 Misra 1992). Since most bacteria are rarely exposed to toxic levels of mercury, the resistance mechanism is inducible and is frequently found on plasmids and/or transposons. Many of the multi-antibiotic resistance plasmids that are frequently found in clinical collections have determinants of mercury resistance as well. Furthermore, mercury resistance is a consistent component of the chromosomal resistance determinant of MRS A (methicillin-resistant Staphylococcus aureus), a current clinical problem and one with no apparent connection to the use of mercurials. If the mercury resistance system is present, the expression of the detoxifying activities is tightly regulated and turned on only when needed. The MerR regulatory protein turns on mRNA synthesis by a positive activator mechanism (for primary references, see Silver and Walderhaug 1992 Misra 1992). 

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Clark, D. L., A. A. Weiss, and S. Silver. 1977. Mercury and organomercurial resistance determined by plasmids in Pseudomonas. J. Bacteriol. 132 186-196. 

Griffin, H. G., T. J. Foster, S. Silver, and T. K. Misra. 1987. Ctoning and DNA sequence of the mercuric- and organomercurial-resistance determinants of the plasmid pDU1358. Biochem. 84 3112-3116... 

Mycobacteria show a high level of resistance to inactivation by biguanides (e.g. chlorhexidine), QACs and organomercurials. Phenols may or may not be... 

Misra, T.K., Bacterial resistances to inorganic mercury salts and organomercurials, Plasmid, 27 (1), 4-16, 1992. 

Robinson, J.B. and O.H. Touvinen. 1984. Mechanisms of microbial resistance and detoxification of mercury and organomercury compounds physiological, biochemical and genetic analysis. Microbiol. Rev. 48 95-124. 

Bizily, S. P., Rugh, C. L., Summers, A. O., and Meagher, R. B., 1999, Phytoremediation of methylmercury pollution merB expression in Arabidopsis thaliana confers resistance to organomercurials, Proc. Natl. Acad. Sci. U.S.A. 96 6808-6813. 

Impermeability (Mycobacteria) Chlorhexidine QACs Organomercurials Glutaraldehyde Waxy cell wall prevents adequate biocide entry Reason for high resistance of some strains of M.chelonael... 

QACs and organomercurials. Phenols may or may not be mycobactericidal. Alkaline glutaralde-hyde exerts a lethal effect but more slowly than against other non-sporulating bacteria, but MAI is more resistant than M. tuberculosis. Recently, glu-taraldehyde-resistant M. chelonae strains have been isolated from endoscope washers. These strains remain sensitive to a new disinfectant used in endoscopy, the aromatic dialdehyde ortho-phthalaldehyde. 

Amongthe Enterobacteriaceae, plasmids may carry genes specifying resistance to antibiotics and in some instances to mercury, organomercury and other cations and some anions. Mercury resistance is inducible and is not the result of training or tolerance. Transposon (Tn)501, conferring mercury resistance, has been widely studied. Plasmids conferring resistance to mercury are of two types ... 

A method for detecting methylmercury in biological samples by its enzymatic conversion to methane is an alternative biological technique for methylmercury or other organomercurial analyses (Baldi and Filippelli 1991). Pseudomonasputida strain FBI, a broad spectrum mercury-resistant strain, is able to enzymatically convert methylmercury to Hg° and methane either in whole cell or in cell-free extracts. GC/FID was used to determine methane produced by the biological derivatization of methylmercury. The detection limit was 15 ng of methylmercury extracted from 1 g of biological tissue. The coefficient of variation was 1.9%. Chemical interferences are negligible in the enzymatic determination of methyl-... 

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