Members of the Faucher lab have a focused interest on host-pathogen interactions, particularly between intracellular pathogens and mammalian macrophages. How one senses the presence of the other, how the regulatory response is organized, and what tools each of them use, are amongst the top questions that are shaping our research. We used transcriptomic tools extensively to answer these questions, and used the data generated from these studies to identify new systems involved in host-pathogen interactions such as virulence factors and regulatory pathways.
L. pneumophila microarray.
Our model organism is Legionella pneumophila, a gram negative pathogen, that can be found in almost any natural or human-made water system. L. pneumophila is able to replicate inside a wide diversity of phagocytic protozoan found in water. It is the causative agent of Legionnaires' disease, an acute form of pneumonia. After inhalation of contaminated water droplets, Legionella infect and replicates inside alveolar macrophages. This phenotype is completely dependant on a Type IVb secretion systems that translocates ~200 effectors inside the host cells. Those effectors modify the normal phagocytic pathway to the benefit of Legionella. Many regulators are known to play a role in the expression of virulence factors, such as two-component systems and small regulatory RNAs (sRNA).
Mechanism of regulation by sRNAs: riboswitch (A), cis-encoded base-pairing sRNA (B), trans-encoded base-pairing sRNA (C), CsrA-CsrB system (D) and the 6S RNA-RNA polymerase system (E). sRNA are colored blue, the mRNA targets are colored in red.