AI-2 of Aggregatibacter actinomycetemcomitans Inhibits Candida albicans Biofilm Formation

Frontiers in Cellular and Infection Microbiology July 2014 | Volume 4 | Article 94 | 1     www.frontiersin.org 

Endang W. Bachtiar 1, Boy M. Bachtiar 1, Lucja M. Jarosz 2†, Lisa R. Amir 1, Hari Sunarto3, Hadas Ganin4, Michael M. Meijler 4 and Bastiaan P. Krom5*


1 Department of Oral Biology, Faculty of Dentistry, Universitas Indonesia, Jakarta, Indonesia
2 Department of Biomedical Engineering, The W.J. Kolff Institute, University Medical Center Groningen and University of Groningen, Groningen, Netherlands
3 Department of Periodontology, Faculty of Dentistry, Universitas Indonesia, Jakarta, Indonesia
4 Department of Chemistry, Ben-Gurion University of the Negev, Be’er-Sheva, Israel
5 Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Free University Amsterdam, Amsterdam,
Netherlands

Aggregatibacter actinomycetemcomitans, a Gram-negative bacterium, and Candida albicans, a polymorphic fungus, are both commensals of the oral cavity but both are opportunistic pathogens that can cause oral diseases. A. actinomycetemcomitans produces a quorum-sensing molecule called autoinducer-2 (AI-2), synthesized by LuxS, that plays an important role in expression of virulence factors, in intra- but also in interspecies communication. The aim of this study was to investigate the role of AI-2 based signaling in the interactions between C. albicans and A. actinomycetemcomitans. A. actinomycetemcomitans adhered to C. albicans and inhibited biofilm formation by means of a molecule that was secreted during growth. C. albicans biofilm formation increased significantly when co-cultured with A. actinomycetemcomitans luxS, lacking AI-2 production. Addition of wild-type-derived spent medium or synthetic AI-2 to spent medium of the luxS strain, restored inhibition of C. albicans biofilm formation to wild-type levels. Addition of synthetic AI-2 significantly inhibited hypha formation of C. albicans possibly explaining the inhibition of biofilm formation. AI-2 of A. actinomycetemcomitans is synthesized by LuxS, accumulates during growth and inhibits C. albicans hypha-and biofilm formation. Identifying the molecular mechanisms underlying the interaction between bacteria and fungi may provide important insight into the balance within complex oral microbial communities.

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Keywords: oral microbiology, interspecies interaction, quorum sensing

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