Characterization of pbt genes conferring increased Pb2+ and Cd2+ tolerance upon Achromobacter xylosoxidans A8

The cluster of pbtTFYRABC genes is carried by plasmid pA81. Its elimination from Achromobacter xylosoxidans A8 resulted in increased sensitivity towards Pb2+ and Cd2+. Predicted pbtTRABC products share strong similarities with Pb2+ uptake transporter PbrT, transcriptional regulator PbrR, metal efflu...

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Published in:Research in microbiology 2013-12, Vol.164 (10), p.1009-1018
Main Authors: Hložková, Kateřina, Šuman, Jáchym, Strnad, Hynek, Ruml, Tomas, Paces, Vaclav, Kotrba, Pavel
Format: Article
Language:English
Subjects:
Achromobacter denitrificans - drug effects
Achromobacter denitrificans - genetics
Achromobacter xylosoxidans
Cadmium
Cadmium - toxicity
Cloning, Molecular
Drug Tolerance
Escherichia coli - drug effects
Escherichia coli - genetics
Gene Expression
Gene Expression Profiling
Gene Expression Regulation, Bacterial - drug effects
Genes, Bacterial
Lead
Lead - toxicity
MerR family
Metal tolerance
Multigene Family
P1-type ATPase
Plasmids
Transcriptional control
Zinc
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Summary:The cluster of pbtTFYRABC genes is carried by plasmid pA81. Its elimination from Achromobacter xylosoxidans A8 resulted in increased sensitivity towards Pb2+ and Cd2+. Predicted pbtTRABC products share strong similarities with Pb2+ uptake transporter PbrT, transcriptional regulator PbrR, metal efflux P1-ATPases PbrA and CadA, undecaprenyl pyrophosphatase PbrB and its signal peptidase PbrC from Cupriavidus metallidurans CH34. Expression of pbtABC or pbtA in a metal-sensitive Escherichia coli GG48 rendered the strain Pb2+-, Cd2+- and Zn2+-tolerant and caused decreased accumulation of the metal ions. Accumulation of Pb2+, but not of Cd2+ or Zn2+, was promoted in E. coli expressing pbtT. Additional genes of the pbt cluster are pbtF and pbtY, which encode the cation diffusion facilitator (CDF)-like transporter and a putative fatty acid hydroxylase of unknown function, respectively. Expression of pbtF did not confer increased metal tolerance upon E. coli GG48, although the protein showed measurable Pb2+-efflux activity. Unlike the pbtT promoter, promoters of pbtABC, pbtF and pbtY contain features characteristic of promoters controlled by metal-responsive transcriptional regulators of the MerR family. Upregulation of pbtABC, pbtF and pbtY upon Pb2+, Cd2+ and Zn2+ exposure was confirmed in wild-type Achromobacter xylosoxidans A8. Gel shift assays proved binding of purified PbtR to the respective promoters.
ISSN:0923-2508
1769-7123
DOI:10.1016/j.resmic.2013.10.002