Metabolite cross-feeding enhances virulence in a model polymicrobial infection

Microbes within polymicrobial infections often display synergistic interactions resulting in enhanced pathogenesis; however,the molecular mechanisms governing these interactions are not well understood. development of model systems that allow detailed mechanistic studies of polymicrobial synergy is a critical step towards a comprehensive understanding of these infections in vivo. in this study,we used a model polymicrobial infection including the opportunistic pathogen aggregatibacter actinomycetemcomitans and the commensal streptococcus gordonii to examine the importance of metabolite cross-feeding for establishing co-culture infections. our results reveal that co-culture with s. gordonii enhances the pathogenesis of a. actinomycetemcomitans in a murine abscess model of infection. interestingly,the ability of a. actinomycetemcomitans to utilize l-lactate as an energy source is essential for these co-culture benefits. surprisingly,inactivation of l-lactate catabolism had no impact on mono-culture growth in vitro and in vivo suggesting that a. actinomycetemcomitans l-lactate catabolism is only critical for establishing co-culture infections. these results demonstrate that metabolite cross-feeding is critical for a. actinomycetemcomitans to persist in a polymicrobial infection with s. gordonii supporting the idea that the metabolic properties of commensal bacteria alter the course of pathogenesis in polymicrobial communities. © 2011 ramsey et al.