Gymnemic Acids Inhibit Adhesive Nanofibrillar Mediated Streptococcus gordonii–Candida albicans Mono-Species and Dual-Species Biofilms

Abstract

Dental 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 microbial biofilms in the oral cavity. Streptococcus gordonii, an early tooth colonizing bacterium and Candida albicans, an opportunistic pathogenic fungus, are the two abundant oral microbes that form mixed biofilms with augmented virulence, affecting oral health negatively. Understanding the molecular mechanisms of the pathogen interactions and identifying non-toxic compounds that block the growth of biofilms are important steps in the development of effective therapeutic approaches. In this in vitro study we report the inhibition of mono-species or dual-species biofilms of S. gordonii and C. albicans, and decreased levels of biofilm extracellular DNA (eDNA), when biofilms were grown in the presence of gymnemic acids (GAs), a non-toxic small molecule inhibitor of fungal hyphae. Scanning electron microscopic images of biofilms on saliva-coated hydroxyapatite (sHA) surfaces revealed attachment of S. gordonii cells to C. albicans hyphae and to sHA surfaces via nanofibrils only in the untreated control, but not in the GAs-treated biofilms. Interestingly, C. albicans produced fibrillar adhesive structures from hyphae when grown with S. gordonii as a mixed biofilm; addition of GAs abrogated the nanofibrils and reduced the growth of both hyphae and the biofilm. To our knowledge, this is the first report that C. albicans produces adhesive fibrils from hyphae in response to S. gordonii mixed biofilm growth. Semi-quantitative PCR of selected genes related to biofilms from both microbes showed differential expression in control vs. treated biofilms. Further, GAs inhibited the activity of recombinant S. gordonii glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Taken together, our results suggest that S. gordonii stimulates the expression of adhesive materials in C. albicans by direct interaction and/or signaling, and the adhesive material expression can be inhibited by GAs.

Recent Advances and Opportunities in the Study of Candida albicans Polymicrobial Biofilms

“…Interestingly, a study by Wan and co-workers (2021) found that the binding force between C. albicans and S. gordonii is approximately 2-fold higher than that between C. albicans and S. mutans. These interactions may also depend on the enhanced production of EXM by PMB (Montelongo-Jauregui et al, 2019) and specific nanostructures, such as C. albicans-produced nanofibrils (Veerapandian and Vediyappan, 2019).…”

Mechanistic Understanding of Candida albicans Biofilm Formation and Approaches for Its Inhibition

“…It decreases the amount of e-DNA present in biofilm. It also inhibits the adhesive property of C. albicans by inhibiting an enzyme glyceraldehyde-3-phosphate dehydrogenase, which is thought to be responsible for the display of adhesion property in C. albicans (Veerapandian and Vediyappan, 2019). Similarly, Waikiloid A 131a prenylated indole alkaloid and polyketide metabolite Waikialide A132 obtained from a Hawaiian Aspergillus spp.…”

Separation of Bioactive Small Molecules, Peptide from Natural Products and Proteins from Pathogenic Microbe by Rotofor-based Preparative Isoelectric Focusing (IEF) Method

“…Out of 20 fractions of G. sylvestre extract obtained from Rotofor IEF, the dark-colored molecules (terpenoid saponins) were migrated and enriched at the anode end (pH 2-3) and the light-yellow clear fractions were observed at cathode end (pH 8-9) ( Figure 2). Aliquots (20 l) from each fraction (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) were separated after reducing and boiling on 15% SDS-PAGE. The Coomassie bluestained gel shows the diffused polypeptide band of about 5 kDa that is enriched in fractions 16-19 ( Figure 3).…”