Transcriptional Analysis of Molecular Interactions between Streptococcus mutans and Candida albicans in Mixed-Biofilms in Cancer Patients

ABSTRACT
Biofilms are intricate cell-to-cell interactions made from multiple species or a singular species that create a protective environment for the pathogen and make medical treatment difficult. Further research is needed to understand the communication and interactions between Streptococcus mutans and Candida albicans within mixed biofilm communities. One hundred samples were obtained from cancer patients with oral gingivitis to examine the mixed-biofilm dynamics of both microorganisms. The patients were selected from attended dentists’ clinics in the Nanakali Cancer Teaching Hospital in Erbil, Kurdistan Region, Iraq, during the period of 2nd April, 2024, to 30th October, 2024. The capability of forming biofilms and their biomass has been evaluated. Molecular and transcriptional analyses were performed using gene expression analysis for ComC, SMU.1396, Ras1, and HWP1 using gyrA and RIP1 as housekeeping genes for Streptococcus mutans and Candida albicans, respectively. The result showed a strong coinfection coordination and biofilm biomass, with increased cell numbers when they occurred together, compared to mono-species biofilms. Indicating coordinative quorum sensing gene expressions. This was evidential using cDNA transcriptional analysis. The gene expression study showed co-regulation of Comc and SMU.1396 in S. mutans, with both the Ras1 and HWP1 genes of C. albicans showing a substantial interaction through quorum sensing. Additionally, both biofilm-related genes in the two species were co-activated in the mixed biofilm, showing a considerable coordination between the genes to form stronger biofilms. To date, our research represents the pioneering investigation into understanding how quorum-sensing and biofilm-forming genes interact and express themselves within mixed biofilm communities.