Proteomics of Streptococcus gordonii within a model developing oral microbial community

BACKGROUND: Streptococcus gordonii is one of several species that can initiate the formation of oral biofilms that develop into the complex multispecies microbial communities referred to as dental plaque. It is in the context of dental plaque that periodontal pathogens such as Porphyromonas gingivalis cause disease. We have previously reported a whole cell quantitative proteomics investigation of P. gingivalis in a model dental plaque community of S. gordonii, P. gingivalis, and Fusobacterium nucleatum. Here we report the adaptation of S. gordonii to the same model. RESULTS: 1122 S. gordonii proteins were detected in S. gordonii control samples, 915 in communities with F. nucleatum, 849 with P. gingivalis, and 649 with all three organisms. Quantitative comparisons showed extensive proteome changes in association with F. nucleatum or P. gingivalis individually or both P. gingivalis and F. nucleatum together. The changes were species specific, though the P. gingivalis interaction may be dominant, indicated by large differences between the proteomes with F. nucleatum or P. gingivalis but limited changes between communities with P. gingivalis or both P. gingivalis and F. nucleatum. The results were inspected manually and an ontology analysis conducted using DAVID. Extensive changes were seen in nutrition pathways with increases in energy metabolism and changes in the resulting byproducts, while the acid and sugar repressed PTS (phosphoenolpyruvate dependent phosphotransferase system) sugar transport systems showed decreases. These results were seen across all the multispecies samples, though with different profiles according to the partner species. F. nucleatum association decreased proteins for the metabolic end products acetate and ethanol but increased lactate, the primary source of acidity from streptococcal cultures. P. gingivalis containing samples had a reduction in levels of proteins for ethanol and formate but increased proteins for both acetate and lactate production. The communities also showed increases in exopolysaccharide synthesis, amino acid biosynthesis, and oxidative stress protection and decreases in adhesion and transporter proteins. CONCLUSION: This study showed that S. gordonii demonstrates species specific responses during interactions with F. nucleatum or P. gingivalis. Extensive changes were seen in energy metabolism and byproduct production implicating nutrient transfer as an important community interaction.