Abstract
ABSTRACTThe 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 periodontal pathogen Porphyromonas gingivalis. C. albicans and P. gingivalis were found to coadhere in both the planktonic and sessile phases. 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 major hyphal protein Als3 showed diminished binding to P. gingivalis, and InlJ interacted with Als3 heterologously expressed in Saccharomyces cerevisiae. Transcriptional profiling by RNA sequencing (RNA-Seq) established that 57 genes were uniquely upregulated in an InlJ-dependent manner in P. gingivalis-C. albicans communities, with overrepresentation of those corresponding to 31 gene ontology terms, 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 P. gingivalis has the potential for increased virulence within such communities.
Highlights
The pleiomorphic yeast Candida albicans is a significant pathogen in immunocompromised individuals
Since the FimA component fimbriae of P. gingivalis are responsible for many adhesive properties of the organism [39, 40], we examined the involvement of FimA in P. gingivalis interactions with candidal hyphae
A fimA-deficient mutant of P. gingivalis did not show a reduction in binding to C. albicans compared to the wild-type parental strain (Fig. 1A), indicating that other surface components of P. gingivalis mediate interspecies adherence
Summary
The pleiomorphic yeast Candida albicans is a significant pathogen in immunocompromised individuals. Of potential relevance to the disease process, C. albicans induced upregulation of components of the type IX secretion apparatus These findings indicate that InlJ-Als3dependent binding facilitates interdomain community development between C. albicans and P. gingivalis and that P. gingivalis has the potential for increased virulence within such communities. Periodontitis ensues from the action of complex heterogeneous microbial communities that inhabit the subgingival compartment [6] Within those communities, organisms can collectively regulate physiological activities, and microbial constituents have developed functional specialization [7,8,9]. Fungi represent a significant component of the oral microbiome [14] Candida species such as C. albicans are common inhabitants of the oral cavity and colonize polymicrobial biofilm communities [15]. We examined the bacterial and fungal adhesins that mediate coadhesion and the influence of interspecies binding on the transcriptome of P. gingivalis
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