Bacterial Genetics and Physiology

Since the pioneering days of the study of bacteria (around the middle of the 19th century with the discovery of the role they play in infectious diseases), scientists have been fascinated by the remarkable capacity of bacteria to adapt to the most diverse and most extreme changes in their environment.

Bacteria are able to adapt in this way because of their tremendous capacity to exchange and rearrange genetic information,which is transported by various vectors: phages (a virus that infects bacteria), transposons (fragments of DNA that can move from one DNA molecule to another) and plasmids.

Plasmids - which most often constitute the extra-chromosomal rings of DNA (independent of the bacterium's chromosome) - play particularly important role in the rapid growth of bacterial populations. Some bacteria have "poison/antidote" systems which allow them to thrive in bacterial populations.

These systems are made up of two elements: a stable protein toxin and an unstable antidote (protein or RNA). The antidote blocks the activity of the toxin and is unstable because it is degraded by an enzyme which is present in all bacteria (generally an ATP-dependent protease). In certain bacterial growth conditions, the instability of the antidote permits the action of the toxin, which results in the death of the bacteria. The recent sequencing of several genomes revealed the existence of similar systems in the chromosome of wide range of forms of bacteria.

The laboratory specializes in the genetic analysis of Escherichia coli as well as its phages, plasmids and transposons. The aim of this research is to understand precisely how the poison/antidote systems work by investigating the targets of the poisons and by analyzing the molecular interactions between poisons and targets in order to develop new classes of antibiotics; by analyzing the molecular interactions between antidotes and ATP-dependent proteases; by analyzing the regulation mechanisms that trigger the programmed death of the bacteria caused by these systems.

In addition, the laboratory is using the poison/antidote systems to develop innovative technological tools. Some of these tools are now used throughout the world in cloning experiments, i.e. the production of DNA fragments which are genetically identical.