Bacteria metal resistance

Naz N, HK Young, N Ahmed, GM Gadd (2005) Cadmium accumulation and DNA homology with metal resistance genes in sulfate-reducing bacteria. Appl Environ Microbiol 71 4610-4618. 

Heavy-metal cations and oxyanions are generally toxic to bacteria although resistance may be induced by various mechanisms after exposure. Attention is drawn to an unusual example in which AF+ may be significant, since the catechol 1,2-dioxygenase and 3,4-dihydroxybenzoate (protocat-echuate) 3,4-dioxygenase that are involved in the metabolism of benzoate by strains of Rhizobium trifolii are highly sensitive to inhibition by AP (Chen et al. 1985). 

Some metals can be converted to a less toxic form through enzyme detoxification. The most well-described example of this mechanism is the mercury resistance system, which occurs in S. aureus,43 Bacillus sp.,44 E. coli,45 Streptomyces lividans,46 and Thiobacillus ferrooxidans 47 The mer operon in these bacteria includes two different metal resistance mechanisms.48 MerA employs an enzyme detoxification approach as it encodes a mercury reductase, which converts the divalent mercury cation into elemental mercury 49 Elemental mercury is more stable and less toxic than the divalent cation. Other genes in the operon encode membrane proteins that are involved in the active transport of elemental mercury out of the cell.50 52... 

Fleck, L. C., Bicca, F. C. and Ayub, M. A. Z. (2000). Physiological aspects of hydrocarbon emulsification, metal resistance and DNA profile of biodegrading bacteria isolated from oil polluted sites, Biotechnol. Lett., 22, 285-289. 

Rani, D. B. R. Mahadevan, A. (1989). Plasmid-encoded metal resistance in bacteria. Journal of Scientific Industrial Research, 48, 338-45. 

Hf, "in, and Mo have been applied to study iron ion and molybdenum ion containing proteins, respectively. Finally, " Cd and " Hg have been used in studies of de novo designed heavy metal ion binding proteins and proteins involved in bacterial heavy metal resistance.Other applications include cadmium and indium binding to bovine serum albumin and DNA, as well as in vivo experiments on bacteria. " ... 

Wildung, R. E., Garland, T. R., and Drucker, H. Complexation of nickel by metal-resistant soil bacteria and fungi, p. 153. "Agronomy Abstracts, ASA, SSSA, and CSSA Annual Meetings."... 

Stephen,. R., Chang, Y.., Macnaughton, S.., Kowalchuk, G. A., Leung, K. T., Plemtning, C. A., et al. (1999). Effect of toxic metals on indigenous soil p-subgroup proteobacterium ammonia oxidizer community structure and protection against toxicity by inoculated metal-resistant bacteria. Appl. Environ. Microbiol. 65, 95—101. 

Th + or AP" " induced a precipitate to form in all Bradyrhizobium and Sinorhi-zobium cultures tested, which suggested a defense mechanism based on metal precipitation by extracellular polymers (Santamaria et al., 2003). Among the metals tested, only Fe " ", Ap+, and Th were able to induce the formation of precipitate. AP+ is probably the natural soil component against which this defence mechanism could be directed, and a different defence mechanism based on extracellular aluminium precipitation within a gelatinous residue has been described for P. fluorescens (Appanna and St. Pierre, 1996). However, tliis polymer was composed mainly of phosphatidylethanolamine. While metal binding to extracellular polymers and bacterial surfaces have been proposed as the reason for increased metal resistance of biofilm-growing bacteria, this proposed defense mechanism involved the physical removal of the capsule after metal binding (Santamaria et al., 2003). 

Lodewyckx, C., Taghavi, S., Mergeay, M., Vangronsveld, J., Clijsters, H., and van der Lelie, D. (2001). The effect of recombinant heavy metal resistant endophytic bacteria in heavy metal uptake by their host plant. Int. J. Phytoremediat. 3, 173-187. 

Nies DH (2000) Heavy metal resistant bacteria as extremophiles molecular physiology and biotechnological use of Ralstonia spec. CH34. Extremophiles 4 77-82. 

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