Arsenic resistance, bacterial

Stinson, S.C. Drag Firms Restock Antibacterial Arsenal, Growing Bacterial Resistance, New Disease Threats Spur Improvements to Existing Drags and Creation of New Classes, Chem Eng. News. 74(39), 75-100 (1996). 

Wang, G., Kennedy, S.P., Fasiludeen, S., Rensing, C., DasSarma, S. (2004). Arsenic resistance in Halobacterium sp. strain NRC-1 examined by using an improved gene knockout system. J. Bacterial. 186 3187-94. 

S Silver, G Ji, S Broer, S Dey, D Dou, BP Rosen. Orphan enzyme or patriarch of a new tribe The arsenic resistance ATPase of bacterial plasmids. Mol Microbiol 8 637-642, 1993. 

Inorganic arsenic oxyanions, frequently present as environmental pollutants, are very toxic for most micro-organisms. Many microbial strains possess genetic determinants that confer resistance. In bacteria, these determinants are often found on plasmids, which has facilitated their smdy to the molecular level. Bacterial plasmids conferring arsenic resistance encode speciflc efflux pumps able to extrude arsenic from the cell cytoplasm, thus lowering the intracellular concentration of the toxic ions. Recently, apparently similar arsenic membrane transport proteins have been found with yeast, plants, and animals (8,9) (see Sec. V, below). 

MOLECULAR GENETICS OF BACTERIAL ARSENIC RESISTANCE VARIETIES OF OPERONS... 

Bacterial resistance to arsenic ions governed by plasmids was first discovered by Novick and Roth (17) in a group of Staphylococcus aureus p-lactamase plasmids that determine resistances to antibiotics and also to heavy metals. Arsenic resistance plasmids confer tolerance to both arsenate and arsenite as well as to antimony (III) (18). Resistance to all three ions is inducible and cross-induction among them occurs (18). Arsenic resistance determinants are very common in plasmids of both gram-negative and gram-positive bacteria. 

Arsenate reductases, initially characterized from plasmid R773 of gramnegative bacteria and plasmid pI258 of gram-positive S. aureus both reduce arsenate to arsenite and both confer arsenate resistance (21,34,36). However, their in vitro measured properties are very different and their energy coupling is different. As the amino acid sequences are only 15% identical, it appears that arsenate reductase enzymatic activity evolved twice independently among bacterial types... 

In addition to plasmid arsenic resistance that is well understood and for which clusters of genes have been isolated and sequenced, there are bacterial arsenic metabolism systems that involve oxidation of arsenite to arsenic. Arsenite oxidation by aerobic pseudomonads was first found with bacteria isolated from cattle dipping solutions where arsenicals were used as agents against ticks around the time of World War I. They were subsequently isolated by Turner and Legge... 

Cl in conjunction with a direct exposure probe is known as desorption chemical ionization (DCI). [30,89,90] In DCI, the analyte is applied from solution or suspension to the outside of a thin resistively heated wire loop or coil. Then, the analyte is directly exposed to the reagent gas plasma while being rapidly heated at rates of several hundred °C s and to temperatures up to about 1500 °C (Chap. 5.3.2 and Fig. 5.16). The actual shape of the wire, the method how exactly the sample is applied to it, and the heating rate are of importance for the analytical result. [91,92] The rapid heating of the sample plays an important role in promoting molecular species rather than pyrolysis products. [93] A laser can be used to effect extremely fast evaporation from the probe prior to CL [94] In case of nonavailability of a dedicated DCI probe, a field emitter on a field desorption probe (Chap. 8) might serve as a replacement. [30,95] Different from desorption electron ionization (DEI), DCI plays an important role. [92] DCI can be employed to detect arsenic compounds present in the marine and terrestrial environment [96], to determine the sequence distribution of P-hydroxyalkanoate units in bacterial copolyesters [97], to identify additives in polymer extracts [98] and more. [99] Provided appropriate experimental setup, high resolution and accurate mass measurements can also be achieved in DCI mode. [100]... 

Arsenate reductase can reduce arsenate to arsenite, and is involved in bacterial resistance to arsenic however, the reduction can also be mediated nonezymatically by reduced glutathione. The arsenate reductase utilizes thioredoxin and glutaredoxin rather than glutathione which is usually postulated to play a role in biomethylation. The cytosolic and periplasmic, two different arsenate reductases, exist in microorganisms encoded by ars and arr systems. Escherichia... 

Lopez-Maury, L., Florencio, F.J., Reyes, J.C. (2003). Arsenic sensing and resistance system in the cyanobacterium Syn-echocystis sp. strain PCC 6803. J. Bacterial. 185 5363-71. 

Silver, S., Nahahara, H. (1983). Bacterial resistance to arsenic compounds. In Industrial, Biomedical, Environmental Perspectives (W.H. Lederer, R.J. Fensterheim, eds), pp. 190-9. Van Nostrand Reinhold, New York. 

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