Antje Munder

Hannover Medical School; Hannover, Germany

Matthias Munder

Max Planck Institute of Molecular Cell Biology and Genetics; Dresden, Germany

Garvis S et al. (2009) PLoS Pathog "Caenorhabditis elegans semi-automated liquid screen reveals a specialized role for the chemotaxis gene cheB2 in Pseudomonas aeruginosa virulence."

Ball G, Munder A, Garvis S, Filloux A, Wiehlmann L, Tummler B, Ewbank JJ, de Bentzmann S

[PLoS Pathog, 2009]

Pseudomonas aeruginosa is an opportunistic human pathogen that causes infections in a variety of animal and plant hosts. Caenorhabditis elegans is a simple model with which one can identify bacterial virulence genes. Previous studies with C. elegans have shown that depending on the growth medium, P. aeruginosa provokes different pathologies: slow or fast killing, lethal paralysis and red death. In this study, we developed a high-throughput semi-automated liquid-based assay such that an entire genome can readily be scanned for virulence genes in a short time period. We screened a 2,200-member STM mutant library generated in a cystic fibrosis airway P. aeruginosa isolate, TBCF10839. Twelve mutants were isolated each showing at least 70% attenuation in C. elegans killing. The selected mutants had insertions in regulatory genes, such as a histidine kinase sensor of two-component systems and a member of the AraC family, or in genes involved in adherence or chemotaxis. One mutant had an insertion in a cheB gene homologue, encoding a methylesterase involved in chemotaxis (CheB2). The cheB2 mutant was tested in a murine lung infection model and found to have a highly attenuated virulence. The cheB2 gene is part of the chemotactic gene cluster II, which was shown to be required for an optimal mobility in vitro. In P. aeruginosa, the main player in chemotaxis and mobility is the chemotactic gene cluster I, including cheB1. We show that, in contrast to the cheB2 mutant, a cheB1 mutant is not attenuated for virulence in C. elegans whereas in vitro motility and chemotaxis are severely impaired. We conclude that the virulence defect of the cheB2 mutant is not linked with a global motility defect but that instead the cheB2 gene is involved in a specific chemotactic response, which takes place during infection and is required for P. aeruginosa pathogenicity.

Wiehlmann L et al. (2007) Int J Med Microbiol "Functional genomics of Pseudomonas aeruginosa to identify habitat-specific determinants of pathogenicity."

Kolmar H, Wiehlmann L, Tummler B, Salunkhe P, Adams T, Munder A, Juhas M

[Int J Med Microbiol, 2007]

Half of all genes in the Pseudomonas aeruginosa genome have either no homology to any previously reported sequence or are homologues of previously reported genes of unknown function. The signature-tagged mutagenesis (STM) screening method allows to explore the role of these hypothetical and unknown proteins for the colonization and persistence of P. aeruginosa in eukaryotic hosts. A plasposon STM library was constructed in the virulent clinical P. aeruginosa isolate TBCF10839 that can persist in polymorphonuclear leukocytes (PMNs). The STM library was screened for plasposon mutants that were attenuated in the killing of the nematode Caenorhabditis elegans, deficient in quorum sensing and production of type II secretion effector proteins or had become more susceptible to killing by PMNs in phagocytosis assays. The three screens revealed in total 69 attenuated mutants. Fifteen mutants that carried the transposon in potential novel virulence determinants of yet unknown function were selected for further analysis. The mutants were characterized in their transcriptome and proteome and their cytotoxicity in vitro and their virulence in worm and mouse infection models in vivo. Previous studies had revealed a remarkable degree of conservation in the virulence mechanisms used by P. aeruginosa to infect hosts of divergent evolutionary origins. Testing of our novel targets did not reveal such a strict conservation. The functional characterization revealed that the fifteen proteins play highly diverse roles in the cell and become habitat-specific virulence factors upon exposure to specific hosts and/or upon exposure to specific stress conditions or host defense mechanisms.

pancreatic A cell fate commitment

The commitment of a cell to a pancreatic A cell and its capacity to differentiate into a pancreatic A cell. A pancreatic A cell is a cell in the pancreas that secretes glucagon.

phosphatidylethanolamine-sterol O-acyltransferase activity

Catalysis of the reaction: a phosphatidylethanolamine + a sterol = a sterol ester + a lysophosphatidylethanolamine.

phosphatidate-sterol O-acyltransferase activity

Catalysis of the reaction: a phosphatidate + a sterol = a sterol ester + a lysophosphatidate.

D-2-hydroxyacid dehydrogenase (quinone) activity

Catalysis of the reaction: a (2R)-2-hydroxycarboxylate + a quinone = a 2-oxocarboxylate + a quinol.

acute eustachian salpingitis

A otosalpingitis with a sudden onset and a short course.

SM lineage cell

A cell that is a sex myoblast or is a lineal descendant of a sex myoblast.