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

• Published in: Microbiology (Society for General Microbiology) Vol. 150; no. 7; pp. 2443 - 2450
• Main Authors: Abbas, Abdelhamid, McGuire, John E, Crowley, Delores, Baysse, Christine, Dow, Max, O'Gara, Fergal
• Format: Journal Article
• Language: English
• Published: England Soc General Microbiol 01.07.2004
• Subjects: Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Gene Expression Regulation, Bacterial; Heat-Shock Response; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Molecular Sequence Data; Mutation; Phloroglucinol - analogs & derivatives; Phloroglucinol - metabolism; Phloroglucinol - pharmacology; Pseudomonas fluorescens; Pseudomonas fluorescens - drug effects; Pseudomonas fluorescens - enzymology; Pseudomonas fluorescens - growth & development; Sequence Analysis, DNA
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.27033-0

BIOMERIT Research Centre, Microbiology Department, National University of Ireland, Cork, Ireland Correspondence Fergal O'Gara f.ogara{at}ucc.ie 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. Abbreviations: PHL, 2,4-diacetylphloroglucinol; MAPG, monoacetylphloroglucinol; TMS, transmembrane segments The GenBank accession number for the sequence reported in this paper is AJ542662 . Present address: Cork Institute of Technology, Cork, Ireland.