Project description:The anaerobic Gram-positive bacterium Propionibacterium acnes is a human skin commensal, but is occasionally associated with inflammatory diseases. Recent work has indicated that evolutionary distinct lineages of P. acnes play etiologic roles in disease while others are associated with health. To shed light on the molecular basis for differential strain properties, we carried out genomic and transcriptomic analysis of distinct P. acnes strains. We sequenced the genome of the P. acnes strain 266, a type I-1a sequence type (ST) 18 strain. Comparative genome analysis of strain 266 and four other P. acnes strains revealed that overall genome plasticity is relatively low; however, a number of island-like genomic regions, encoding a variety of putative virulence-associated and fitness traits, differ between phylotypes. Comparative transcriptome analysis revealed that 225 genes of strain KPA171202 (type I-2, ST34) were differentially transcribed in strain 266 during exponential growth. 47% of these genes belong to the strain-specific gene content of strain KPA171202, indicating that strain-specific functions are utilized. Next, we studied differential expression during exponential and stationary growth phases. Genes encoding components of the energy-conserving respiratory chain as well as secreted and virulence-associated factors were transcribed during the exponential phase, while the stationary growth phase was characterized by up-regulation of genes involved in the stress response and amino acid metabolism. Taken together, our data highlight the genomic basis for strain diversity and identify, for the first time, the transcribed part of the genome, underling the important role active growth plays in the inflammatory activity of P. acnes. We argue that the disease-causing potential of different P. acnes strains is not only determined by variable genome content but also, and to a greater degree, by variable transcriptomes.
