Insights into Dynamic Polymicrobial Synergy Revealed by Time-Coursed RNA-Seq.

Many bacterial infections involve polymicrobial communities in which constituent organisms are synergistically pathogenic. Periodontitis, a commonly occurring chronic inflammatory disorder, is induced by multispecies bacterial communities. The periodontal keystone pathogen and the accessory pathogen exhibit polymicrobial synergy in animal models of disease. Mechanisms of co-adhesion and community formation by and are well-established; however, little is known regarding the basis for increased pathogenicity. In this study we used time-coursed RNA-Seq to comprehensively and quantitatively examine the dynamic transcriptional landscape of in a model consortium with . Genes encoding a number of potential virulence determinants had higher relative mRNA levels in the context of dual species model communities than alone, including adhesins, the Type IX secretion apparatus, and tetratricopeptide repeat (TPR) motif proteins. In contrast, genes encoding conjugation systems and many of the stress responses showed lower levels of expression in . A notable exception to reduced abundance of stress response transcripts was the genes encoding components of the oxidative stress-related OxyR regulon, indicating an adaptation of to detoxify peroxide produced by the streptococcus. Collectively, the results are consistent with evolutionary adaptation of to a polymicrobial oral environment, one outcome of which is increased pathogenic potential.