While the commensal bacterium Propionibacterium acnes (P. acnes) is involved in the maintenance of a healthy skin, it can also act as an opportunistic pathogen in acne vulgaris. The latest findings on P. acnes shed light on the critical role of a tight equilibrium between members of its phylotypes and within the skin microbiota in the development of this skin disease. Indeed, contrary to what was previously thought, proliferation of P. acnes is not the trigger of acne as patients with acne do not harbour more P. acnes in follicles than normal individuals. Instead, the loss of the skin microbial diversity together with the activation of the innate immunity might lead to this chronic inflammatory condition. This review provides results of the most recent biochemical and genomic investigations that led to the new taxonomic classification of P. acnes renamed Cutibacterium acnes (C. acnes), and to the better characterisation of its phylogenetic cluster groups. Moreover, the latest data on the role of C. acnes and its different phylotypes in acne are presented, providing an overview of the factors that could participate in the virulence and in the antimicrobial resistance of acne-associated strains. Overall, this emerging key information offers new perspectives in the treatment of acne, with future innovative strategies focusing on C. acnes biofilms and/or on its acne-associated phylotypes.

New insights into Legionella pneumophila biofilm regulation by c-di-GMP signaling.(2016) Biofouling, Open Archive TOULOUSE Archive Ouverte (OATAO) OATAO is an open access repository that collects the work of some Toulouse researchers and makes it freely available over the web where possible. This is an author's version published in : http://oatao.univ-toulouse.fr/19753Official URL : https://doi.org/10. 1080/08927014.2016.1212988 Any correspondence concerning this service should be sent to the repository administrator : tech-oatao@listes-diff.inp-toulouse.fr The waterborne pathogen Legionella pneumophila grows as a bio lm, freely or inside amoebae. Cyclic-di-GMP (c-di-GMP), a bacterial second messenger frequently implicated in bio lm formation, is synthesized and degraded by diguanylate cyclases (DGCs) and phosphodiesterases (PDEs), respectively. To characterize the c-di-GMP-metabolizing enzymes involved in L. pneumophila bio lm regulation, the consequences on bio lm formation and the c-di-GMP concentration of each corresponding gene inactivation were assessed in the Lens strain. The results showed that one DGC and two PDEs enhance di erent aspects of bio lm formation, while two proteins with dual activity (DGC/PDE) inhibit bio lm growth. Surprisingly, only two mutants exhibited a change in global c-di-GMP concentration. This study highlights that speci c c-di-GMP pathways control L. pneumophila bio lm formation, most likely via temporary and/or local modulation of c-di-GMP concentration. Furthermore, Lpl1054 DGC is required to enable the formation a dense bio lm in response to nitric oxide, a signal for bio lm dispersion in many other species. New insights into Legionella pneumophila bio lm regulation by c-di-GMP signaling