3-Chlorobenzoate is taken up by a chromosomally encoded transport system in Cupriavidus necator JMP134.
Cupriavidus necator JMP134(pJP4) is able to grow on 3-chlorobenzoate (3-CB), a model chloroaromatic pollutant. Catabolism of 3-CB is achieved via the expression of the chromosomally encoded benABCD genes and the tfd genes from plasmid pJP4. Since passive diffusion of benzoic acid derivatives at physiological pH is negligible, the uptake of this compound should be facilitated by a transport system. However, no transporter has so far been described to perform this function, and identification of chloroaromatic compound transporters has been limited. In this work, uptake experiments using 3-[ring-UL-(14)C]CB showed an inducible transport system in strain JMP134, whose expression is activated by 3-CB and benzoate. A similar level of 3-CB uptake was found for a mutant strain of JMP134, defective in chlorobenzoate degradation, indicating that metabolic drag is not an important component of the measured uptake rate. Competitive inhibitor assays showed that uptake of 3-CB was inhibited by benzoate and, to a lesser degree, by 3-CB and 3,5-dichlorobenzoate, but not by any of 12 other substituted benzoates tested. The expression of several gene candidates for this transport function was analysed by RT-PCR, including both permease-type and ABC-type ATP-dependent transporters. Induction of a chromosomally encoded putative permease transporter (benP gene) was found specifically in the presence of 3-CB or benzoate. A benP knockout mutant of strain JMP134 displayed an almost complete loss of 3-CB transport activity. This is to our knowledge the first report of a 3-CB transporter.
Departamento de Genética Molecular y Microbiología and Millennium Nucleus on Microbial Ecology and Environmental Microbiology and Biotechnology, and Center for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
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T
Ledger
Departamento de Genética Molecular y Microbiología and Millennium Nucleus on Microbial Ecology and Environmental Microbiology and Biotechnology, and Center for Advanced Studies in Ecology and Biodiversity, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
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Aceituno
Facultad de Ingeniería y Ciencia, Universidad Adolfo Ibáñez, 7941169 Santiago, Chile.
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B
González
D000890:Anti-Infective Agents / Q000494:pharmacology; D001565:Benzoates / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002723:Chlorobenzoates / Q000378:metabolism*; D002875:Chromosomes / Q000378:metabolism*; D020118:Cupriavidus necator / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005810:Multigene Family; D010957:Plasmids; D012329:RNA, Bacterial / Q000032:analysis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015533:Transcriptional Activation
D000890:Anti-Infective Agents; D001565:Benzoates; D002723:Chlorobenzoates; D012329:RNA, Bacterial; C036427:3-chlorobenzoic acid