Propionibacterium genomics to decipher remarkable phenotypic biodiversity of strains and adaptations to substrates and environment.

International audiencePropionibacterium genomics to decipher remarkable phenotypic biodiversity of strains and adaptation to substrates and environments Hélène Falentin The genus Propionibacterium belongs to the class of Actinobacteria (Gram +, high GC content). They are non-spore-forming, microaerophylic pleomorphic rods. They possess 2.5-3 Mb circular chromosome. They synthetise propionate and acetate as main metabolites, are able to grow without amino acid addition and survive to stationary phase. Up to now, seventeen species have been sequenced. Several complete genomes are available for P. acnes, P. freudenreichii, P. avidum and P. acidipropionici species. Among human species, comparative genomics pointed out (i) genes responsible for exopolysaccharide production in P. avidum and (ii) camp genes involved in P. acnes hemolytic activity. At infraspecific level, comparison of P. acnes genomes revealed pathogenicity island, comparison of P. freudenreichii revealed genetic basis (genomic islands, major gene or mutations) responsible for sugar degradation, lipolytic and anti-inflammatory activities. Transcriptomics deciphered adaptation of P. acnes and P. freudenreichii to growth phases and different environments (cold, colonic conditions) in pure culture. At community level, metagenomics highlights a peculiar structure of P. acnes population, and strains specific to acneic skins. In the next few years, the impact of environment, and bacterial interactions have to be taken into account for a deep investigation of Propionibacterium fonctionality at ecosystem level