AMINO SUGARS RESHAPE INTERACTIONS BETWEEN STREPTOCOCCUS MUTANS AND STREPTOCOCCUS GORDONII
Amino sugars, particularly glucosamine (GlcN) and N-acetylglucosamine (GlcNAc) are abundant carbon and nitrogen sources that are continually supplied in host secretions and the diet to biofilms colonizing the human mouth. Evidence is emerging that these amino sugars may provide an ecological advantage to beneficial commensals over oral pathobionts. Here we performed transcriptome analysis on Streptococcus mutans and Streptococcus gordonii growing in single-species or dual-species cultures with glucose, GlcN or GlcNAc as the primary carbohydrate source. Compared to glucose, GlcN caused drastic transcriptomic shifts in each bacterium when they were cultured alone. Likewise, co-cultivation in the presence of GlcN yielded transcriptomic profiles that were dramatically different than the single-species results from GlcN-grown cells. In contrast, GlcNAc elicited only minor changes in the transcriptome of either organism, in both single- and dual-species cultures. Interestingly, genes involved in pyruvate metabolism were among the most significantly affected by GlcN in both species, and these changes were consistent with measurements of pyruvate in culture supernates. Differing a previous report, growth of S. mutans alone with GlcN inhibited expression of multiple operons required for mutacin production. Co-cultivation with S. gordonii consistently increased the expression by S. mutans of two manganese transporter operons (slo and mntH) and decreased expression of mutacin genes. Conversely, S. gordonii appeared to be less affected by the presence of S. mutans, but did show increases in genes for biosynthetic processes in the co-cultures. In conclusion, amino sugars profoundly altered the interactions between the pathogen and the commensal, likely by reprogramming their central metabolism. Overall design: mRNA profiling of Streptococcus mutans and Streptococcus gordonii, each grown to exponential phase in batch on a TV medium supplemented with glucose, GlcN, or GlcNAc, in the form of single-species and mixed-species cultures.