ActA is required for crossing of the fetoplacental barrier by Listeria monocytogenes.

The facultative intracellular bacterial pathogen Listeria monocytogenes induces severe fetal infection during pregnancy. Little is known about the molecular mechanisms allowing the maternofetal transmission of bacteria. In this work, we studied fetoplacental invasion by infecting mice with various mutants lacking virulence factors involved in the intracellular life cycle of L.

Lessons from signature-tagged mutagenesis on the infectious mechanisms of pathogenic bacteria.

Studies on the genetic basis of bacterial pathogenicity have been undertaken for almost 30 years, but the development of new genetic tools in the past 10 years has considerably increased the number of identified virulence factors. Signature-tagged mutagenesis (STM) is one of the most powerful general genetic approaches, initially developed by David Holden and colleagues in 1995, which has now led to the identification of hundreds of new genes requested for virulence in a broad range of bacterial pathogens. We have chosen to present in this review, the most recent and/or most significant contributions to the understanding of the molecular mechanisms of bacterial pathogenicity among over 40 STM screens published to date.

Identification of the agr locus of Listeria monocytogenes: role in bacterial virulence.

Listeria monocytogenes is a gram-positive facultative intracellular food-borne pathogen that can cause severe infections in humans and animals. We have recently adapted signature-tagged transposon mutagenesis (STM) to identify genes involved in the virulence of L. monocytogenes.

Capacity of ivanolysin O to replace listeriolysin O in phagosomal escape and in vivo survival of Listeria monocytogenes.

Listeriolysin O (LLO, hly-encoded) is a major virulence factor secreted by the pathogen Listeria monocytogenes. The amino acid sequence of LLO shows a high degree of similarity with that of ivanolysin O (ILO), the cytolysin secreted by the ruminant pathogen Listeria ivanovii. Here, it was tested whether ILO could functionally replace LLO by expressing the gene encoding ILO under the control of the hly promoter, in an hly-deleted strain of L.

Functional assembly of two membrane-binding domains in listeriolysin O, the cytolysin of Listeria monocytogenes.

Listeriolysin O (LLO) is a major virulence factor secreted by the pathogenic Listeria monocytogenes and acts as pore-forming cytolysin. Based on sequence similarities between LLO and perfringolysin (PFO), the cytolysin from Clostridium perfringens of known crystallographic structure, two truncated LLO proteins were produced: LLO-d123, comprising the first three predicted domains, and LLO-d4, the last C-terminal domain. The two proteins were efficiently secreted into the culture supernatant of L.