AUTHOR=Bachtiar Endang W. , Bachtiar Boy M. , Jarosz Lucja M. , Amir Lisa R. , Sunarto Hari , Ganin Hadas , Meijler Michael M. , Krom Bastiaan P. 

TITLE=AI-2 of Aggregatibacter actinomycetemcomitans inhibits Candida albicans biofilm formation

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=4

YEAR=2014

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2014.00094

DOI=10.3389/fcimb.2014.00094

ISSN=2235-2988

ABSTRACT=<p><italic>Aggregatibacter actinomycetemcomitans</italic>, a Gram-negative bacterium, and <italic>Candida albicans</italic>, a polymorphic fungus, are both commensals of the oral cavity but both are opportunistic pathogens that can cause oral diseases. <italic>A. actinomycetemcomitans</italic> 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 <italic>C. albicans</italic> and <italic>A. actinomycetemcomitans</italic>. <italic>A. actinomycetemcomitans</italic> adhered to <italic>C. albicans</italic> and inhibited biofilm formation by means of a molecule that was secreted during growth. <italic>C. albicans</italic> biofilm formation increased significantly when co-cultured with <italic>A. actinomycetemcomitans luxS</italic>, lacking AI-2 production. Addition of wild-type-derived spent medium or synthetic AI-2 to spent medium of the <italic>luxS</italic> strain, restored inhibition of <italic>C. albicans</italic> biofilm formation to wild-type levels. Addition of synthetic AI-2 significantly inhibited hypha formation of <italic>C. albicans</italic> possibly explaining the inhibition of biofilm formation. AI-2 of <italic>A. actinomycetemcomitans</italic> is synthesized by LuxS, accumulates during growth and inhibits <italic>C. albicans</italic> 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.</p>