After studying chemistry in Lille (France), Pascale Cossart obtained a master degree at Georgetown University, Washington DC, in 1971. Back in France she obtained her PhD in Paris, in 1977 working with G. Cohen in the Pasteur Institute where she is still now. Her thesis project was the amino-acid sequence determination of an E coli enzyme. During her postdoctorate with M. Yaniv, she sequenced the gene encoding this enzyme, thrA, the first gene sequenced in the Pasteur Institute. In the early 80’s, she switched to the study of DNAprotein interactions and together with B. Gicquel, collaborated with J. Beckwith in Harvard toanalyze the site-specificity of the E. coli cyclic AMP binding protein. In 1986, she started agroup within the Unit headed by Julian Davies and embarked on her work on Listeria monocytogenes, an bacterium responsible for food borne infections that she had chosen as a model to study intracellular parasitism. She created her own independant group in 1991. P.
Cossart has been a pioneer in the field of Cellular Microbiology. She has used an unprecedented combination of innovative approaches to unravel the mechanisms underlying Listeria infection. She discovered a series of virulence factors which helped generating general concepts in infection biology, including ActA which together with Arp2/3 mediates actin-based motility and the two major invasion proteins internalin and InlB which trigger actin rearrangements upon bacterial entry into cells. She dissected in great details the cell biology of the infectious process, in particular, the signaling events occurring upon entry into cells and during intra– and intercellular movements. She also discovered unsuspected posttranslational modifications in the host and how bacteria trigger a transient mitochondrial fission by a non classical pathway. She also highlighted the thermoregulation of expression of virulence genes via a previously never described mechanism, an RNA thermosensor. At the animal level, following her discovery of a species-specificity, using transgenic mice expressing the human receptor, she highlighted how the bacteria can cross the intestinal barrier through the interaction of internalin with E-cadherin. More recently, she has reported several important papers revealing how bacteria remodel chromatin in order to escape innate immune responses. She has also had major contributions in non coding RNA biology in bacteria and discovered in particular that riboswitches are more versatile than previously described being able to regulate non coding RNAs in particular antisense RNAs and protein sequestering RNAs. Listeria is now one of the most documented bacterial pathogens and areference in infection biology.
P. Cossart and her group are now using this bacterium as a model to investigate both the cross talk between the bacterium and the host and also independently the bacterium and the host themselves in order to establish fundamental principles in microbiology, in cell biology and in epigenetics.