Team GME, UMR MICALIS

The GME team studies the pathogenic and adaptive properties of the spore-forming bacteria of the Bacillus cereus sensu lato group, as well as Clostridioides difficile. To reach our objectives we rely on molecular genetics and biochemistry approaches combined with single-cell imaging technologies and the use of the versatile infection model Galleria mellonella. As a direct result of our fundamental research, biotechnological applications in the fields of human health, food safety and crop protection also form a significant part of the GME team's activities.

The B. cereus sensu lato group comprises taxonomically closely related spore-forming bacteria capable of colonizing hosts as diverse as mammals and insects. We study in particular Bacillus thuringiensis (Bt), an entomopathogenic species used as a biopesticide due to its production of Cry insecticidal proteins, and B. cereus sensu stricto (Bc), a species responsible for human food poisoning. The ability of these bacteria to form biofilms and highly-adherent spores, which are widely distributed in the environment, leads to recurrent contamination of foodstuffs and equipment used by the agri-food industry. These bacteria are also opportunistic pathogens that can cause local or systemic nosocomial infections (endocarditis, pneumonia, septicemia, endophthalmitis). In the frame of insect as a new source for feed and food; the insect health and the microbial safety have been investigated with particular focus on the impact and avoidance of Bt and Bc.

Clostridioides difficile (Cd) is an anaerobic and spore-forming entero-pathogen that is able to jump across host species and represents a One Health problem. This opportunist behavior is controlled by the host microbiota: it can be eliminated or asymptomatically carried in a healthy host, but, after an antibiotic treatment, microbiota dysbiosis favors Cd emergence as a pathogen. Its secreted toxins cause diarrhea that are difficult to treat and recurrent. Like those of many pathogens, Cd biofilms could be involved in antibio-tolerance, persistence and infection recurrence.