New genes involved in chromate resistance inRalstonia metallidurans strain CH34
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- Juhnke, S., Peitzsch, N., Hübener, N. et al. Arch Microbiol (2002) 179: 15. doi:10.1007/s00203-002-0492-5
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Chromate resistance inRalstonia metallidurans CH34 is based on chromate efflux catalyzed by ChrA efflux pumps. The bacterium harbors two chromate resistance determinants, the previously knownchr1 on plasmid pMOL28 (geneschrI, chrB1,chrA1,chrC, chrE, chrF1) andchr2 on the chromosome (geneschrB2,chrA2,chrF2). Deletion of the geneschrl, chrC, chrA2,chrB2 andchrF2 influenced chromate resistance and transcription from achrBp1::lacZ fusion. Deletion of the plasmid-encoded genechrBx did not change chromate resistance orchrBp1 regulation. Northern hybridization and primer-extension experiments were used to study transcription of the plasmid-encodedchr1 determinant. Transcription ofchrB1,chrA1 andchrC was induced by chromate. The presence of sulfate influenced transcription positively. ThechrBp1,chrAp1 andchrCp promoters showed some similarity to heat-shock promoters. Transcription of the generpoH encoding a putative heat-shock sigma factor was also induced by chromate, butrpoH was not essential for chromate resistance. The ChrC protein was purified as a homotetramer and exerted superoxide dismutase activity. Thus, possible regulators for chromate resistance (Chrl, ChrB1, ChrB2, ChrF1, and ChrF2) and an additional detoxification system (ChrC) were newly identified as parts of chromate resistance inR. metallidurans.
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KeywordsChromate resistanceRalstonia metalliduransAlcaligenes eutrophus