3-Chlorobenzoate is taken up by a chromosomally encoded transport system in Cupriavidus necator JMP134

Abstract

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-14C]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.

Hierarchy of Carbon Source Utilization in Soil Bacteria: Hegemonic Preference for Benzoate in Complex Aromatic Compound Mixtures Degraded by Cupriavidus pinatubonensis Strain JMP134

“…Such a mechanism of degradation repression is operative in P. putida and A. baylyi (21,23). However, this is not probable, because uptake of AC takes place without the need for specific transporters at the concentrations used here (20,46,47). Bz control by activation of a putative outward transport system (e.g., an efflux pump) is also a possibility, but the little available evidence seems to indicate a role in antibiotic resistance, at least for a salicylic acid efflux pump (48).…”

Transcriptome differences between Cupriavidus necator NH9 grown with 3-chlorobenzoate and that grown with benzoate

“…A BLASTP analysis was performed to compare the amino acid sequences of the eight transporters of NH9 with those that have been experimentally veri ed or functionally analyzed (Table S5). The products of BJN34_18155 and BJN34_32125 exhibited more than 70% amino acid sequence identities with BenP (a 3-CB transporter) [35]. The products of BJN34_30890 and BJN34_33870 showed moderate identities (> 50%) with MhbT (a 3-HBA transporter) [36] and PcaK (a 4-HBA transporter) [37,38], respectively (Table 2).…”

The LysR-type PcaQ protein regulates expression of a protocatechuate-inducible ABC-type transport system in Sinorhizobium meliloti

“…While systems involved in the active transport of aromatic acids such as protocatechuate have been described in many species, including Pseudomonas putida (Harwood et al, 1994;Nichols & Harwood, 1997), a protocatechuate transport system has yet to be identified in S. meliloti or any other member of the a-proteobacteria. Furthermore, S. meliloti appears to lack protein homologues of the PcaK major facilitator superfamily of aromatic acid transport proteins (Collier et al, 1997;Williams & Shaw 1997;D'Argenio et al, 1999;Ledger et al, 2009).…”