Community Development between Porphyromonas gingivalis and Candida albicans Mediated by InlJ and Als3

The pleiomorphic yeast Candida albicans is a significant pathogen in immunocompromised individuals. In the oral cavity, C. albicans is an inhabitant of polymicrobial communities, and interspecies interactions promote hyphal formation and biofilm formation. C. albicans colonizes the subgingival area, and the frequency of colonization increases in periodontal disease. In this study, we investigated the interactions between C. albicans and the periodontalpathogen Porphyromonas gingivalis. C. albicans and P. gingivalis were found to co-adhere both in the planktonic and sessile phase. Loss of the Internalin-family protein InlJ abrogated adhesion of P. gingivalis to C. albicans, and recombinant InlJ protein competitively inhibited interspecies binding. A mutant of C. albicans deficient in expression of the major hyphal protein Als3 showed diminished binding to P. gingivalis, and InlJ interacted with Als3 heterologously expressed in Saccharomyces cerevisiae. Transcriptional profiling by RNA-Seq established that 57 genes were uniquely upregulated in an InlJ-dependent manner in P. gingivalis-C. albicans communities, with 31 gene ontology terms over-represented including those associated with growth and division. Of potential relevance to the disease process, C. albicans induced upregulation of components of the Type IX secretion apparatus. Collectively, these findings indicate that InlJ-Als3 dependent binding facilitates interdomain community development between C. albicans and P. gingivalis, and that within these communities P gingivalis has the potential for increased virulence.