AI-2 of Aggregatibacter actinomycetemcomitans inhibits Candida albicans biofilm formation

Abstract

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.

Riemerella anatipestifer lacks luxS, but can uptake exogenous autoinducer-2 to regulate biofilm formation

“…Biofilm formation was enhanced in Eikenella corrodens [26] by the addition of AI-2, while AI-2 inhibited biofilm formation in Candida albicans [27] and Bacillus cereus [28]. In the present study, our results showed that AI-2 inhibited RA biofilm formation.…”

Fungi at the Scene of the Crime: Innocent Bystanders or Accomplices in Oral Infections?

“…In vitro, A. actinomycetemcomitans adheres to hyphae, although interactions with C. albicans show decreased fungal biofilm formation which is mediated by the luxS-synthesised autoinducer-2 (AI-2)-dependent mechanism. This was also mirrored using the 4,5-dihydroxy-2,3-pentanedione (DPD) synthetic molecule [45]. In Streptococcus gordonii, a ubiquitous oral commensal, it was shown that C. albicans hyphal formation was induced in a luxS-dependent manner, and that the addition of DPD had no effect on hyphal formation [13].…”

The Effect of Curcuma Xanthorrhiza Ethanol Extract on the Viability of Streptococcus Mutans and Aggregatibacter Actinomycetemcomitans (Dental Biofilm Research: In Vitro Study)

“…This could explain why dual-species biofilm is more resistant than single-species S. mutans biofilm. Moreover, gene involved in resistance to antibacterial compounds could be transferred from one bacterial cell, such as A. actinomycetemcomitans, to another bacterial cell in the biofilm in this study, S. mutans so that the overall resistance of the biofilm was increased [24,25]. In addition, in dualspecies biofilm, the curcuma ethanol extract may have been able to hinder the growth of S. mutans but not A. actinomycetemcomitans due to differences in the composition of the membrane cells of the two bacteria.…”

“…According to the Basic Health Research (Riset Kesehatan Dasar), the percentage of the Indonesian population with oral and dental health problems was 23.3% in 2007 and increased to 25.9% in 2013 [1]. Of all oral and dental diseases, dental caries, and periodontal disease were found most often found in this population [2].…”