Mercuric Reductase Enzymes from Streptomyces Species and Group B Streptococcus

Nakahara, Hideomi; Schottel, Janet L.; Yamada, Toshihiko; Miyakawa, Yozo; Asakawa, Misaki; Harville, Jerome; Silver, Simón

doi:10.1099/00221287-131-5-1053

Cited by 21 publications

(27 citation statements)

References 20 publications

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“…3B and C) is characteristic of a thermophilic enzyme. The stability of MR from gram-negative bacteria at temperatures exceeding 80°C was reported previously; the Tn501 enzyme retained full activ- on May 7, 2018 by guest http://aem.asm.org/ ity when it was tested at 37°C following a 10-min incubation at 100°C (24). However, MR activity at elevated temperatures was not reported previously.…”

Section: Discussionmentioning

confidence: 63%

Mercury Adaptation among Bacteria from a Deep-Sea Hydrothermal Vent

Vetriani

Chew²,

Miller

et al. 2005

Appl Environ Microbiol

117

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Since deep-sea hydrothermal vent fluids are enriched with toxic metals, it was hypothesized that (i) the biota in the vicinity of a vent is adapted to life in the presence of toxic metals and (ii) metal toxicity is modulated by the steep physical-chemical gradients that occur when anoxic, hot fluids are mixed with cold oxygenated seawater. We collected bacterial biomass at different distances from a diffuse flow vent at 9°N on the East Pacific Rise and tested these hypotheses by examining the effect of mercuric mercury [Hg(II)] on vent bacteria. Four of six moderate thermophiles, most of which were vent isolates belonging to the genus Alcanivorax, and six of eight mesophiles from the vent plume were resistant to >10 M Hg(II) and reduced it to elemental mercury [Hg(0)]. However, four psychrophiles that were isolated from a nearby inactive sulfide structure were Hg(II) sensitive. A neighbor-joining tree constructed from the deduced amino acids of a PCR-amplified fragment of merA, the gene encoding the mercuric reductase (MR), showed that sequences obtained from the vent moderate thermophiles formed a unique cluster (bootstrap value, 100) in the MR phylogenetic tree, which expanded the known diversity of this locus. The temperature optimum for Hg(II) reduction by resting cells and MR activity in crude cell extracts of a vent moderate thermophile corresponded to its optimal growth temperature, 45°C. However, the optimal temperature for activity of the MR encoded by transposon Tn501 was found to be 55 to 65°C, suggesting that, in spite of its original isolation from a mesophile, this MR is a thermophilic enzyme that may represent a relic of early evolution in high-temperature environments. Results showing that there is enrichment of Hg(II) resistance among vent bacteria suggest that these bacteria have an ecological role in mercury detoxification in the vent environment and, together with the thermophilicity of MR, point to geothermal environments as a likely niche for the evolution of bacterial mercury resistance.Heavy metals are highly enriched in hydrothermal vent fluids of mid-oceanic ridge systems (35), reaching concentrations that are considered to be toxic to living organisms (26). The steep physical-chemical gradients that occur when reduced, hot, element-and sulfur-rich vent fluids are diluted with oxygenated, cold seawater create a gradient in metal toxicity in the vent environment (20). As oxygen mixes with the anoxic, sulfur-rich fluid, metal speciation can shift from metal sulfides that show poor bioavailability and low toxicity to more soluble and oxidized forms with increased bioavailability and toxicity. With such a change in metal speciation, high tolerance to metals is expected among microbes inhabiting niches of the vent ecosystem where mixing between hydrothermal fluids and oxygenated seawater occurs, such as diffuse flow vents and associated plumes. This hypothesis is supported by experimental data showing that thermophilic archaea and bacteria from highly reduced vent microhabitats were metal su...

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Section: Discussionmentioning

confidence: 63%

Mercury Adaptation among Bacteria from a Deep-Sea Hydrothermal Vent

Vetriani

Chew²,

Miller

et al. 2005

Appl Environ Microbiol

117

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“…These HgRe enzymes also exhibit a trimodal heat sensitivity pattern, with loss of activity between 60 and 80°C. Thus the mechanism of mercury resistance appears to be the same as has been defined in numerous other gram-positive bacterial species (12,16).…”

Section: Discussionmentioning

confidence: 71%

“…The pattern of heat stability of these mycobacterial HgRe resembles that of other gram-positive bacteria (e.g., S. aureus) in that it is relatively heat labile, although it exhibits some species differences. This activity differed from that of the HgRe of the gram-negative bacterium E. coli, which is heat stable and has activity at 80 to 90°C (12) (Table 4 …”

Section: Resultsmentioning

confidence: 94%

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Mercuric reductase activity and evidence of broad-spectrum mercury resistance among clinical isolates of rapidly growing mycobacteria

Steingrube

Wallace

Steele

et al. 1991

Antimicrob Agents Chemother

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“…Because of this versatility, actinomycetes are important in biotechnology and have been employed in bioremediation, including metal recovery. Mercury resistance was ¢rst reported in actinomycetes [1] with inducible mercuric resistance in Streptomyces lividans 1326, a laboratory strain. Subsequently, Sedlmeier and Altenbuchner [2] cloned and analyzed the mercuric resistance operon.…”

Section: Introductionmentioning

confidence: 99%

Mercury-resistant actinomycetes from the Chesapeake Bay

Ravel

1998

FEMS Microbiology Letters

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Two actinomycete strains, CHR3 and CHR28, were isolated from metal-contaminated sediments from Baltimore Inner Harbor. The isolates were classified as Streptomyces spp. Agar diffusion assays showed both isolates to be resistant to mercuric chloride and phenylmercuric acetate. Hybridization experiments indicated that genes homologous to the mercuric reductase and organomercurial lyase of Streptomyces lividans 1326 were present in strains CHR3 and CHR28. Strain CHR28 grew at both low and high salt concentrations; however, strain CHR3 showed enhanced growth in the presence of salt, evidence of its habitat being marine or estuarine sediment. z 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V.

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Mercuric Reductase Enzymes from Streptomyces Species and Group B Streptococcus

Cited by 21 publications

References 20 publications

Mercury Adaptation among Bacteria from a Deep-Sea Hydrothermal Vent

Mercury Adaptation among Bacteria from a Deep-Sea Hydrothermal Vent

Mercuric reductase activity and evidence of broad-spectrum mercury resistance among clinical isolates of rapidly growing mycobacteria

Mercury-resistant actinomycetes from the Chesapeake Bay

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