Gene expression and metabolic activity of Streptococcus mutans during exposure to dietary carbohydrates glucose, sucrose, lactose and xylitol

Recent RNA-seq studies have given us a deeper insight into the cariogenic impact of carbohydrate sources in the bacterium Streptococcus mutans, the principal etiological agent of human dental caries. The process of dental caries development is given by the ability of this bacterium to ferment some carbohydrates up to organic acids contributing to the pH decrease in the oral cavity and the demineralization of the enamel. Besides, in dental caries progression, an important role is played by biofilm formation, which starts and ends with free planktonic cells, and it is given by several unique properties called virulence factors. The most cariogenic carbohydrate is considered sucrose, an easily metabolizable source of energy inducing acidification and synthesis of glucans forming typical bacterial cell clumps. By using multifaceted methodological approaches, we compared the transcriptomic and metabolomic profiles of S. mutans growing in planktonic culture on preferred and non-preferred carbohydrates and fasting conditions. Lactose and xylitol showed high effectiveness in the regulation of the IPS metabolism, cell wall structure and overall virulence involved in the initial phase of biofilm formation and structure but with an opposite pattern compared to sucrose and glucose. These findings confirm the recent results that xylitol and lactose play a vital role in biofilm structure but do not reduce its formation related to their cariogenic potential. Overall design: Identification of transcriptomic changes of S. mutans depending on different carbohydrate source - glucose, sucrose, lactose and xylitol, each in triplicate; and cultivation without sugar as control