Roles Played by MerE and MerT in the Transport of Inorganic and Organic Mercury Compounds in Gram-negative Bacteria

Sone, Yuka; Pan-Hou, Hidemitsu; Nakamura, Ryosuke; Sakabe, Kou; Kiyono, Masako

doi:10.1248/jhs.56.123

Cited by 24 publications

(10 citation statements)

References 12 publications

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“…Module G carries the Tn1696 merE-DACPTR gene cluster which codes for resistance to mercury (24). Based on similarities to Tn21 counterparts, MerA is predicted to function as a mercuric reductase, while MerE and MerT (inner membrane proteins) and MerP (periplasmic protein) are hypothesized to constitute key structural components of the mercury transport system itself (30). The 4.0-kb module K carries the annotated genes sup and orf4 and the 5= remnant of uspA.…”

Section: Resultsmentioning

confidence: 99%

Deletion of Tn AbaR23 Results in both Expected and Unexpected Antibiogram Changes in a Multidrug-Resistant Acinetobacter baumannii Strain

Kochar

Crosatti

Harrison

et al. 2012

Antimicrob Agents Chemother

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ABSTRACTSince the 2006 discovery of theAcinetobacter baumanniistrain AYE AbaR1 resistance island, similar elements have been reported in numerous members of this species. As AbaR1 is distantly related to Tn7, we have renamed it TnAbaR1. TnAbaRtransposons are known to carry multiple antibiotic resistance- and efflux-associated genes, although none have been experimentally studieden bloc. We deleted the TnAbaRtransposon inA. baumanniiA424, which we have designated TnAbaR23, and characterized independent deletion mutants DCO163 and DCO174. The NotI pulsed-field gel electrophoresis (PFGE) profile of strain DCO174 was consistent with targeted deletion of TnAbaR23alone, but strain DCO163 apparently harbored a second large genomic deletion. Nevertheless, “subtractive amplification” targeting 52 TnAbaRand/or resistance-associated loci yielded identical results for both mutants and highlighted genes lost relative to strain A424. PCR mapping and genome sequencing revealed the entire 48.3-kb sequence of TnAbaR23. Consistent with TnAbaR23carrying two copies ofsul1, both mutants exhibited markedly increased susceptibility to sulfamethoxazole. In contrast, loss oftetAR(A) resulted in only a minor and variable increase in tetracycline susceptibility. Despite not exhibiting a growth handicap, strain DCO163 was more susceptible than strain DCO174 to 9 of 10 antibiotics associated with mutant-to-mutant variation in susceptibility, suggesting impairment of an undefined resistance-associated function. Remarkably, despite all three strains sharing identicalgyrAandparCsequences, the ciprofloxacin MIC of DCO174 was >8-fold that of DCO163 and A424, suggesting a possible paradoxical role for TnAbaR23in promoting sensitivity to ciprofloxacin. This study highlights the importance of experimental scrutiny and challenges the assumption that resistance phenotypes can reliably be predicted from genotypes alone.

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Section: Resultsmentioning

confidence: 99%

Deletion of Tn AbaR23 Results in both Expected and Unexpected Antibiogram Changes in a Multidrug-Resistant Acinetobacter baumannii Strain

Kochar

Crosatti

Harrison

et al. 2012

Antimicrob Agents Chemother

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“…The Mer transporters MerE, and MerT along with the periplasmic protein MerP are found in many Hg-resistant bacteria and have been shown to be effective transporters of Hg(II) [ 19 – 21 ] and MeHg [ 22 ] into the cells where they are transformed by the Mer system (MerA and/or MerB). However, to date there is little information on the bioavailability of thiol-bound Hg to these Hg-resistant bacteria, and what roles the Mer transport system play in the uptake of Hg from such complexes.…”

Section: Introductionmentioning

confidence: 99%

The Use of a Mercury Biosensor to Evaluate the Bioavailability of Mercury-Thiol Complexes and Mechanisms of Mercury Uptake in Bacteria

Ndu

Barkay

Schartup³

et al. 2015

PLoS ONE

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As mercury (Hg) biosensors are sensitive to only intracellular Hg, they are useful in the investigation of Hg uptake mechanisms and the effects of speciation on Hg bioavailability to microbes. In this study, bacterial biosensors were used to evaluate the roles that several transporters such as the glutathione, cystine/cysteine, and Mer transporters play in the uptake of Hg from Hg-thiol complexes by comparing uptake rates in strains with functioning transport systems to strains where these transporters had been knocked out by deletion of key genes. The Hg uptake into the biosensors was quantified based on the intracellular conversion of inorganic mercury (Hg(II)) to elemental mercury (Hg(0)) by the enzyme MerA. It was found that uptake of Hg from Hg-cysteine (Hg(CYS)2) and Hg-glutathione (Hg(GSH)2) complexes occurred at the same rate as that of inorganic complexes of Hg(II) into Escherichia coli strains with and without intact Mer transport systems. However, higher rates of Hg uptake were observed in the strain with a functioning Mer transport system. These results demonstrate that thiol-bound Hg is bioavailable to E. coli and that this bioavailability is higher in Hg-resistant bacteria with a complete Mer system than in non-resistant strains. No difference in the uptake rate of Hg from Hg(GSH)2 was observed in E. coli strains with or without functioning glutathione transport systems. There was also no difference in uptake rates between a wildtype Bacillus subtilis strain with a functioning cystine/cysteine transport system, and a mutant strain where this transport system had been knocked out. These results cast doubt on the viability of the hypothesis that the entire Hg-thiol complex is taken up into the cell by a thiol transporter. It is more likely that the Hg in the Hg-thiol complex is transferred to a transport protein on the cell membrane and is subsequently internalized.

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“…One mer -operon encodes a mercuric transport protein (MerE, HALZIN_916) for organic mercury uptake [ 51 ], a transcriptional regulator (MerD, HALZIN_917), three alkylmercury lyases (MerB, HALZIN_918-920) catalyzing organomercurials yielding Hg 2+ [ 52 ] and a transcriptional regulator (MerR, HALZIN_922). The other one encodes a transcriptional regulator (MerR, HALZIN_2469), two mercuric transport proteins (MerT and MerP, HALZIN_2470-2471) for inorganic mercury uptake [ 51 ] and a mercuric reductase (MerA, HALZIN_2472) catalyzing Hg 2+ to Hg 0 [ 53 ]. According to the genomic data, H. zincidurans strain B6 T is able to survive in both inorganic and organic mercury environments.…”

Section: Insights Into the Genomementioning

confidence: 99%

High quality draft genome sequence of the heavy metal resistant bacterium Halomonas zincidurans type strain B6T

Huo

Cheng

et al. 2014

Stand in Genomic Sci

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Halomonas zincidurans strain B6T was isolated from a deep-sea heavy metal rich sediment from the South Atlantic Mid-Ocean Ridge. The strain showed significant resistance to heavy metals, especially to zinc. Here we describe the genome sequence and annotation, as well as the features, of the organism. The genome contains 3,325 protein-coding genes (2,848 with predicted functions), 61 tRNA genes and 6 rRNA genes. H. zincidurans strain B6T encodes 31 genes related to heavy metal resistance. And HGT may play an important role in its adaption to the heavy metal rich environment. H. zincidurans strain B6T may have potential applications in the bioremediation of heavy metal-contaminated environments.

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Roles Played by MerE and MerT in the Transport of Inorganic and Organic Mercury Compounds in Gram-negative Bacteria

Cited by 24 publications

References 12 publications

Deletion of Tn AbaR23 Results in both Expected and Unexpected Antibiogram Changes in a Multidrug-Resistant Acinetobacter baumannii Strain

Deletion of Tn AbaR23 Results in both Expected and Unexpected Antibiogram Changes in a Multidrug-Resistant Acinetobacter baumannii Strain

The Use of a Mercury Biosensor to Evaluate the Bioavailability of Mercury-Thiol Complexes and Mechanisms of Mercury Uptake in Bacteria

High quality draft genome sequence of the heavy metal resistant bacterium Halomonas zincidurans type strain B6T

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