An E. coli Gene emrD Is Involved in Adaptation to Low Energy Shock

Naroditskaya, V.; Schlösser, Manfred; Fang, Nan; Lewis, Kim

doi:10.1006/bbrc.1993.2320

Cited by 46 publications

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“…This suggests that the phlE gene of P. fluorescens F113 may be transcriptionally independent of phlD and could be transcribed from a s 54 -dependent promoter. (Paulsen & Sukurray, 1993;Yoshida et al, 1990), E. coli Bcr (Bentley et al, 1993) and EmrD (Naroditskaya et al, 1993), and Bacillus subtilis Bmr (Neyfakh et al, 1991) and Blt (Ahmed et al, 1995). These proteins are members of the major facilitator superfamily having 12 TMS.…”

Section: Resultsmentioning

confidence: 99%

The putative permease PhlE of Pseudomonas fluorescens F113 has a role in 2,4-diacetylphloroglucinol resistance and in general stress tolerance

et al. 2004

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2,4-Diacetylphloroglucinol (PHL) is the primary determinant of the biological control activity of Pseudomonas fluorescens F113. The operon phlACBD encodes enzymes responsible for PHL biosynthesis from intermediate metabolites. The phlE gene, which is located downstream of the phlACBD operon, encodes a putative permease suggested to be a member of the major facilitator superfamily with 12 transmembrane segments. PhlE has been suggested to function in PHL export. Here the sequencing of the phlE gene from P. fluorescens F113 and the construction of a phlE null mutant, F113-D3, is reported. It is shown that F113-D3 produced less PHL than F113. The ratio of cell-associated to free PHL was not significantly different between the strains, suggesting the existence of alternative transporters for PHL. The phlE mutant was, however, significantly more sensitive to high concentrations of added PHL, implicating PhlE in PHL resistance. Furthermore, the phlE mutant was more susceptible to osmotic, oxidative and heat-shock stresses. Osmotic stress induced rapid degradation of free PHL by the bacteria. Based on these results, we propose that the role of phlE in general stress tolerance is to export toxic intermediates of PHL degradation from the cells. INTRODUCTIONMany Pseudomonas fluorescens strains produce 2,4-diacetylphloroglucinol (PHL) (Bangera & Thomashow, 1996;Boruah & Kumar, 2002;Nowak-Thompson et al., 1994;Reddi & Borovkov, 1970; Sharifi-Tehrani et al., 1998). This phenolic molecule has broad-spectrum antifungal (Levy et al., 1992;Schoonbeek et al., 2002;Tomas-Lorente et al., 1989;Weller & Cook, 1983), antibacterial (Levy et al., 1992), antihelminthic (Bowden et al., 1965; Harrison et al., 1993) and phytotoxic (Keel et al., 1992;Reddi et al., 1969) activities. PHL is the primary determinant of biological control by P. fluorescens F113 (Shanahan et al., 1992). Synthesis of PHL is directed by the phlACBD genes, which are believed to constitute an operon (Bangera & Thomashow, 1996Delany, 1999). PhlD shows structural similarities with plant chalcone synthase, also called polyketide synthase type III, and is necessary but not sufficient for the synthesis of monoacetylphloroglucinol (MAPG) (Bangera & Thomashow, 1999). PhlA, PhlC and PhlB are necessary and sufficient for the transacetylation of MAPG to produce PHL (Bangera & Thomashow, 1999;Shanahan et al., 1992). The available data strongly suggest that PhlA, PhlC, PhlB and PhlD function in a multienzyme complex (Bangera & Thomashow, 1999;Delany, 1999). Expression of the phlACBD operon is subject to complex regulation (Aarons et al., 2000;Abbas et al., 2002;Bangera & Thomashow, 1999;Chou et al., 1993;Corbell & Loper, 1995;Delany, 1999; Delany et al., 2000;Duffy & Defago, 1999;Schnider-Keel et al., 2000). In addition, PHL is an autoregulator, positively influencing its own biosynthesis (Abbas et al., 2002;Schnider-Keel et al., 2000).Micro-organisms have developed various ways to resist the toxic effects of the secondary metabolites they produce. These mechanisms include expo...

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Section: Resultsmentioning

confidence: 99%

The putative permease PhlE of Pseudomonas fluorescens F113 has a role in 2,4-diacetylphloroglucinol resistance and in general stress tolerance

et al. 2004

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“…P32482) (11), and the multidrug resistance proteins EmrD (accession no. P31442) (47) and MdfA (accession no. CAA69997) (28) of E. coli.…”

Section: Resultsmentioning

confidence: 99%

BordetellaAlcS Transporter Functions in Alcaligin Siderophore Export and Is Central to Inducer Sensing in Positive Regulation of Alcaligin System Gene Expression

Brickman

Armstrong

2005

J Bacteriol

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Bordetella pertussis and Bordetella bronchiseptica, which are respiratory mucosal pathogens of mammals, produce and utilize the siderophore alcaligin to acquire iron in response to iron starvation. A predicted permease of the major facilitator superfamily class of membrane efflux pumps, AlcS (synonyms, OrfX and Bcr), was reported to be encoded within the alcaligin gene cluster. In this study, alcS null mutants were found to be defective in growth under iron starvation conditions, in iron source utilization, and in alcaligin export. trans complementation using cloned alcS genes of B. pertussis or B. bronchiseptica restored the wild-type phenotype to the alcS mutants. Although the levels of extracellular alcaligin measured in alcS strain culture fluids were severely reduced compared with the wild-type levels, alcS mutants had elevated levels of cell-associated alcaligin, implicating AlcS in alcaligin export. Interestingly, a ⌬alcA mutation that eliminated alcaligin production suppressed the growth defects of alcS mutants. This suppression and the alcaligin production defect were reversed by trans complementation of the ⌬alcA mutation in the double-mutant strain, confirming that the growth-defective phenotype of alcS mutants is associated with alcaligin production. In an alcA::mini-Tn5 lacZ1 operon fusion strain background, an alcS null mutation resulted in enhanced AlcR-dependent transcriptional responsiveness to alcaligin inducer; conversely, AlcS overproduction blunted the transcriptional response to alcaligin. These transcription studies indicate that the alcaligin exporter activity of AlcS is required to maintain appropriate intracellular alcaligin levels for normal inducer sensing and responsiveness necessary for positive regulation of alcaligin system gene expression.

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“…Membrane transporters of the MF family possess 12 to 14 transmembrane domains. For example, Bcr (Escherichia coli) (1), EmrB (E. coli) (19), EmrD (E. coli) (29), MdfA/Cmr (E. coli) (6,32), NorA (Staphylococcus aureus) (58), QacA (S. aureus) (45), and Bmr (Bacillus subtilis) (30) are members of this family, and these systems mediate drug extrusion with different specificities. Transporters of the SMR family are rather small and usually possess four transmembrane domains.…”

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confidence: 99%

Analysis of a Complete Library of Putative Drug Transporter Genes in Escherichia coli

2001

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The complete sequencing of bacterial genomes has revealed a large number of drug transporter genes. In Escherichia coli, there are 37 open reading frames (ORFs) assumed to be drug transporter genes on the basis of sequence similarities, although the transport capabilities of most of them have not been established yet. We cloned all 37 putative drug transporter genes in E. coli and investigated their drug resistance phenotypes using an E. coli drug-sensitive mutant as a host. E. coli cells transformed with a plasmid carrying one of 20 ORFs, i.e., fsr, mdfA, yceE, yceL, bcr, emrKY, emrAB, emrD, yidY, yjiO, ydhE, acrAB, cusA (formerly ybdE), yegMNO, acrD, acrEF, yhiUV, emrE, ydgFE, and ybjYZ, exhibited increased resistance to some of the 26 representative antimicrobial agents and chemical compounds tested in this study. Of these 20 ORFs, cusA, yegMNO, ydgFE, yceE, yceL, yidY, and ybjYZ are novel drug resistance genes. The fsr, bcr, yjiO, ydhE, acrD, and yhiUV genes gave broader resistance spectra than previously reported.

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An E. coli Gene emrD Is Involved in Adaptation to Low Energy Shock

Cited by 46 publications

References 0 publications

The putative permease PhlE of Pseudomonas fluorescens F113 has a role in 2,4-diacetylphloroglucinol resistance and in general stress tolerance

The putative permease PhlE of Pseudomonas fluorescens F113 has a role in 2,4-diacetylphloroglucinol resistance and in general stress tolerance

BordetellaAlcS Transporter Functions in Alcaligin Siderophore Export and Is Central to Inducer Sensing in Positive Regulation of Alcaligin System Gene Expression

Analysis of a Complete Library of Putative Drug Transporter Genes in Escherichia coli

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