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An efflux pump is required for siderophore recycling by Pseudomonas aeruginosa
Author(s) -
Yeterian Emilie,
Martin Lois W.,
Lamont Iain L.,
Schalk Isabelle J.
Publication year - 2010
Publication title -
environmental microbiology reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.229
H-Index - 69
ISSN - 1758-2229
DOI - 10.1111/j.1758-2229.2009.00115.x
Subject(s) - periplasmic space , pyoverdine , efflux , siderophore , bacteria , extracellular , biochemistry , pseudomonas aeruginosa , chemistry , secretion , microbiology and biotechnology , biology , escherichia coli , gene , genetics
Summary Pyoverdine (PVDI) is a siderophore produced by Pseudomonas aeruginosa in order to obtain iron. This molecule is composed of a fluorescent chromophore linked to an octapeptide. Following secretion from the bacteria, PVDI chelates iron ions and the resulting Fe‐PVDI complexes are taken up by the bacteria through a cell surface receptor protein. The iron is released in the periplasm and the resulting PVDI is recycled, being secreted out of the bacteria by a previously unknown mechanism. Three genes with the potential to encode an efflux system are adjacent to, and coregulated with, genes required for PVDI‐mediated iron transport. Mutation of genes encoding this efflux pump (named PvdRT‐OpmQ) prevented recycling of PVDI from the periplasm into the extracellular medium. Fluorescence microscopy showed that in the mutant bacteria PVDI accumulated in the periplasm. Gallium (Ga 3+ ), a metal that cannot be removed from PVDI by reduction, is taken up by P. aeruginosa when chelated by PVDI. Recycling did not occur after transport of PVDI–Ga 3+ and fluorescence accumulated in the periplasm even when the PvdRT‐OpmQ efflux pump was functional. Cellular fractionation showed that PVDI‐synthesizing bacteria lacking PvdRT‐OpmQ secreted PVDI but had an approximately 20‐fold increase in the amount of PVD present in the periplasm, consistent with an inability to recycle PVDI. Collectively, these data show that PvdRT‐OpmQ is involved in recycling of PVDI from the periplasm to the extracellular medium and recycling requires release of the metal ion from PVDI.