Research directions
Study of Staphylococcus aureus and Streptococcus gordonii pathogenesis in experimental endocarditis
Microbial pathogenesis is a multistep phenomenon starting with colonization of host tissues, followed by successful bacterial settlement and eventually tissue destruction and invasion. Staphylococci are particularly well-equipped in both surface determinants mediating tissue adherence and colonization, and secreted enzymes and toxins promoting tissue destruction and diseases. The redundancy of staphyloccocal virulence determinants makes it difficult to study them in knock-out mutants. Therefore, we have developed an heterologous gene expression system allowing the study of individual pathogenic genes in the thoroughgate Lactococcus lactis. The system has helped understand the role of several staphylococcal proteins in experimental endovascular infections. Moreover, expressing truncated S. aureus proteins in Lactococci and studying them in experimental endocarditis has revealed that cooperation between several distinct protein adherence domains (i.e., adherence to fibrinogen and fibronectin) was critical for successful infection. This dual in vitro and in vivo approach is successfully used to understand endovascular infection by other endocarditis pathogens including Streptococci
Evolution and adaptation of bacteria to degrade toxic chemicals
One of our special interests is to study how bacteria evolve and adapt to use organic pollutants as novel growth substrates. To be able to 'consume' organic pollutants, the bacteria have to recognize them as 'food' and then synthesize enzymes catalyzing the stepwise conversion of the pollutant into useful products for the cell. The diversity of existing catabolic enzymes in different bacteria in nature is extremely large Therefore, there are numerous ways for degradation of organic compounds in the environment
More interestingly, there is still an ongoing process of arisal of new enzyme variants and new combinations of existing enzymes. Such bacteria which display new degradation capabilities are actually very often selected in polluted environments Their genetic study reveals that various different specialized biochemical mechanisms operate in the cell which change the DNA. Sometimes these changes involve only small base-pair alterations, whereas others involve large DNA regions or even mobilization of DNA fragments to other bacteria (horizontal gene transfer). Call it evolution
Current projects in this topic study the specificities and modes of action of self-transmissable genomic islands and the genetic characterization of pathways for degradation of hexachlorocyclohexane and mecoprop
Development of whole cell bacterial biosensors
Bacteria perceive their environment through specific molecular signals which are intercepted by receptor proteins in the cell. Such receptors are often regulatory proteins, which are capable of binding to the DNA and transmitting the perceived signal to promote transcription. By coupling the DNA binding sites for these regulators to a gene for an easily measurable enzyme or protein, whole cell bacterial biosensors can be constructed in the laboratory. Such bacteria react to the presence of the signal by producing the marker protein, which can be quantified
By using regulatory proteins for pollutant degradation, we constructed whole cell bacterial biosensors for linear alkanes, naphthalene, toluene, 2,4-dichlorophenoxyacetic acid, arsenic and 2-hydroxybiphenyl. These bacteria emit light or fluorescence whenever they encounter their target compounds, in aqueous concentration ranges between 10 nM and 10 µM
Current themes focus on mutagenizing the regulatory components in order to achieve new effector recognition capabilities, on field-testing of an arsenic biosensor in developing countries and on using single-cell information to study bioavailability of poorly water-soluble pollutants
Competences
Biologie moléculaire des bactéries
Analyse moléculaire des facteurs de virulence bactérienne
Analyse moléculaire des mécanismes de résistance
Nouvelles stratégies thérapeutiques
Modèles animaux
Etude de la pathologie des infections endovasculaires
Biochimie et génétique de la paroi bactérienne
Génomique microbienne et génométrie
