Genomics of Microbial Pathogens - CNRS URA2171  

  HEADDr KUNST Frank /
Dr GLASER Philippe / Dr JULES Matthieu

  Annual Report

The research aim of the Unit is to better understand the evolution and the adaptation of the opportunistic bacterial pathogens Listeria monocytogenes, Legionella pneumophila and Streptococcus agalactiae to the host and to the environment.

The genus Listeria (teams C. Buchrieser, P. Glaser)

In collaboration with the German Network PathGenoMik we have analyzed the complete genome sequences of representative isolates of all known Listeria species. Additionally, more than 400 Listeria strains of different origins have been compared by DNA array hybridization. Apparently lower virulence of some strains may be correlated with missing genes, e.g. encoding surface proteins and internalins. This information is further exploited to gain a better understanding of evolution and virulence within the genus Listeria.

The genus Legionella (team C. Buchrieser)

The genus Legionella comprises ~50 species, including the human pathogen L.  pneumophila, the causative agent of Legionnaires’ disease. The interaction with amoeba seems to be the driving force in the evolution of its pathogenicity. Genome sequencing and analysis of two L. pneumophila isolates identified an unexpected high number and variety of eukaryotic-like proteins (Cazalet et al., 2004). To understand when these proteins may act and how their expression is regulated, we have developed multiple genome-based microarrays. In vivo transcriptome studies in the Acanthamoeba castellanii model revealed a life cycle dependent gene expression program; e.g. virulence genes are mainly expressed in the late stage of the life cycle. Furthermore, new insight into the regulation of the intracellular lifecycle of L. pneumophila was obtained (Brüggemann et al., 2006). Studies are under way to better understand the complex regulatory network governing this life cycle and to elucidate how the newly identified putative virulence factors and eukaryotic-like proteins subvert host cell functions.

The genus Streptococcus (team P. Glaser)

It comprises more than 40 species widely distributed among men and animals. S. agalactiae, a colonizer of the gastrointestinal and urogenital tracts, is the major cause of neonatal infections causing pneumonia, septicaemia and meningitis. Comparative genomics and biodiversity studies of a representative panel of Streptococcus isolates revealed a mosaic genome organization with a conserved backbone, 14 genome islands and a high variability of genes encoding surface components (Glaser et al., 2002; Brochet et al., 2006). Two islands represent a new class of transposase dependent conjugative transposons. The mechanism of transposition and conjugation are under investigation. The cell surface plays a major role in the interaction with the host. To understand its biogenesis and to identify vaccine candidates, we developed a high throughput screening procedure to analyze large collections of insertion mutants and of natural isolates using biological markers such as surface polysaccharides and protein antigens.


Publications 2006 of the unit on Pasteur's references database

Activity Reports 2006 - Institut Pasteur
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