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BMC Microbiol. 2010 Apr 24;10:124. doi: 10.1186/1471-2180-10-124.

Cell-associated hemolysis activity in the clinical strain of Pseudomonas fluorescens MFN1032.

Author information

1
Laboratory of cold microbiology signals and the microenvironment, LMDF-SME, UPRES EA 4312, University of Rouen, 55 rue Saint Germain, 27000 Evreux, France.

Abstract

BACKGROUND:

MFN1032 is a clinical Pseudomonas fluorescens strain able to grow at 37 degrees C. MFN1032 cells induce necrosis and apoptosis in rat glial cells at this temperature. This strain displays secretion-mediated hemolytic activity involving phospholipase C and cyclolipopeptides. Under laboratory conditions, this activity is not expressed at 37 degrees C. This activity is tightly regulated and is subject to phase variation.

RESULTS:

We found that MFN1032 displays a cell-associated hemolytic activity distinct from the secreted hemolytic activity. Cell-associated hemolysis was expressed at 37 degrees C and was only detected in vitro in mid log growth phase in the presence of erythrocytes. We studied the regulation of this activity in the wild-type strain and in a mutant defective in the Gac two-component pathway. GacS/GacA is a negative regulator of this activity. In contrast to the Pseudomonas fluorescens strains PfO-1 and Pf5, whose genomes have been sequenced, the MFN1032 strain has the type III secretion-like genes hrcRST belonging to the hrpU operon. We showed that disruption of this operon abolished cell-associated hemolytic activity. This activity was not detected in P.fluorescens strains carrying similar hrc genes, as for the P. fluorescens psychrotrophic strain MF37.

CONCLUSIONS:

To our knowledge this the first demonstration of cell-associated hemolytic activity of a clinical strain of Pseudomonas fluorescens. Moreover, this activity seems to be related to a functional hrpU operon and is independent of biosurfactant production. Precise link between a functional hrpU operon and cell-associated hemolytic activity remains to be elucidated.

PMID:
20416103
PMCID:
PMC2871272
DOI:
10.1186/1471-2180-10-124
[Indexed for MEDLINE]
Free PMC Article

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