Mechanisms of microbial resistance and detoxification of mercury and organomercury compounds: physiological, biochemical, and genetic analyses.

Abstract

the populations of seed-feeding birds (32). High levels of methylmercury have also been detected in fish from the Great Lakes region of North America. Mercury and organomercurial compounds are highly toxic. Methylmercury is 100 times more toxic than inorganic mercury and has been found to be mutagenic under experimental conditions (26). The solubility of inorganic and organic mercury compounds in lipids as well as their binding to sulfhydryl groups of proteins in membranes and enzymes (4) account for their cytotoxicity. Sources of mercury in the environment are both natural and anthropogenic in origin. In nature, cinnabar (red HgS) and metacinnabar (black HgS) are the most important mercury-containing ores. Livingstonite (HgSb4S7) and mercury-containing sulfide minerals such as tetrahydrite (6Cu2S * Sb2S3) are also considered important sources (18).

Fate of genetically modified Rhizobium leguminosarum biovar viciae during long‐term storage of commercial inoculants

“…Such difference was greatest in the case of plasmid-borne modifications, likely due to the plasmid copy number. The same applies to the level of mercury resistance (Silver and Misra 1988) which, moreover, was found to be influenced by the medium used, being lower in mannitol-based media (data not shown), presumably due to an interference between mannitol metabolism and mercury detoxification, as reported by Robinson and Tuovinen (1984).…”

Environmental factors affecting the formation of methylmercury in low pH lakes

“…Because fish tissues and organs do not methylate mercury [ 12,131, the elevated mercury levels of fish in acidic lakes must be a result of increased bioaccumulation of methylmercury. Methylmercury is produced by the methylation of inorganic mercury (Hg[II]) [14] in the terrestrial environment [15], in the water column [16] and sediment of lakes [17], and in the intestines [18] and external slime layer of fish 1191.…”

“…The observation that the lake water column and the sediment-water interface appear to be more important than subsurface sediments in regulating the enhanced methylmercury production in low pH lakes is initially surprising. The biological methylation of mercury was first demonstrated in sediments [ 171, and sediments have long been assumed to be the major site of methylation [14,16,58,112]. Although the potential for mercury methylation may be greater in subsurface sediments, the greater volume of the water column may result in it playing a more important role in the whole-lake production of methylmercury.…”

Plasmid-encoded mercury resistance in a Pseudomonas stutzeri strain that degrades o-xylene

“…While Pseudomonas narrow spectrum resistance plasmids confer the ability to volatilize mercury only from inorganic Hg 2+, Pseudomonas broad spectrum plasmids confer the ability to volatilize mercury from both Hg 2+ and some organomercurials after the cleavage of the carbon-mercury linkage by a lyase. In the case of broad spectrum plasmids, PMA and Thimerosal act as inducers of mercury reductase, while for narrow spectrum plasmids they are poor inducers [27]. We demonstrated the presence, in cell-extracts of P. stutzeri OX, of a mercury reductase activity, induced by mercuric chloride and by PMA and Thimerosal.…”

“…The Hg r plasmids of Pseudomonas fall into two classes of resistance: narrow-spectrum plasmids that confer resistance to Hg 2+, merbromin, fluorescein mercuric acetate (FMA), and a low-level resistance to p-hydroxymercuribenzoate (pHMB), and broad spectrum plasmids that confer resistance to phenylmercuric acetate (PMA), Thimerosal, ethylmercuric chloride (EMC), meth- ylmercuric chloride (MMC), and pHMB in addition to the foregoing compounds [27]. We investigated the capacity of pPB to confer resistance to organomercurials.…”