Inhibition of adhesive nanofibrillar mediatedStreptococcus gordonii - Candida albicansmono- and dual-species biofilms

Abstract

AbstractDental caries and periodontitis are the most common oral disease of all age groups, affecting billions of people worldwide. These oral diseases are mostly associated with the microbial biofilms in the oral cavity.Streptococcus gordonii, an early tooth colonizing bacterium andCandida albicans, an opportunistic pathogenic fungus, are the two abundant oral microbes form mixed biofilms and augment their virulence properties affecting oral health negatively. Understanding the molecular mechanisms of their interactions and blocking the growth of these biofilms by nontoxic compounds could help develop effective therapeutic approaches. We report in this study, inhibition of mono- or dual-species biofilms ofS. gordoniiandC. albicans, and biofilm eDNAin vitroby Gymnemic Acids (GAs), a nontoxic small molecule inhibitor of fungal hyphae. Scanning electron microscopic images of biofilms revealed attachment ofS. gordoniicells to the hyphal and on saliva-coated hydroxyapatite (sHA) surfaces via nanofibrils only in the untreated control but not in the GAs treated biofilms. Interestingly,C. albicansproduced fibrillar adhesive structures from hyphae when grown withS. gordoniias mixed biofilm and addition of GAs to this biofilm abrogates the nanofibrils, reduces the growth of hyphae, and biofilms. To our knowledge, this is a first report thatC. albicansproduces adhesive fibrils from hyphae in response toS. gordoniimixed biofilm growth. A semi-quantitative PCR data of selected genes related to biofilms of both microbes show their differential expression. Further evaluation of one of the gene products ofS. gordoniirevealed that GAs could inhibit its recombinant glyceraldehyde-3-phosphate dehydrogenase (GAPDH) enzyme activity. Taken together, our results suggest thatS. gordoniistimulates expression of adhesive materials inC. albicansby direct interaction and or by signaling mechanism(s), and these mechanisms can be inhibited by GAs. Further studies on global gene expression of these biofilms and their biochemical studies may reveal the molecular mechanism of their inhibition.