Growth with Commensal Streptococci Alters Streptococcus mutans Behaviors

Abstract

As oral bacteria grow and persist within biofilms attached to the tooth’s surface, they interact with other species to form synergistic or antagonistic exchanges that govern homeostasis for the overall population. One example are the interactions between the cariogenic species Streptococcus mutans and oral commensal streptococci. Previously, we showed that the cell–cell signaling pathways of S. mutans were inhibited during coculture with other oral streptococci species, leading us to posit that the S. mutans transcriptome and behaviors are broadly altered during growth with these species. To test this hypothesis, we performed whole transcriptome sequencing (RNA-seq) on cocultures of S. mutans with either Streptococcus gordonii, Streptococcus sanguinis, or Streptococcus oralis and a quadculture containing all 4 species in comparison to S. mutans grown alone. Our results reveal that in addition to species-dependent changes to the S. mutans transcriptome, a conserved response to oral streptococci in general can be observed. We monitored the behavior of S. mutans by both microscopy imaging of biofilms and in a bacteriocin overlay assay and verified that S. mutans acts similarly with each of these species but noted divergences in phenotypes when cocultured with another cariogenic Streptococcus ( Streptococcus sobrinus) or with oral nonstreptococci species. RNA-seq with oral nonstreptococci showed lack of a consistent gene expression profile and overlap of differentially expressed genes found with commensal streptococci. Finally, we investigated the role of upregulated S. mutans genes within our data sets to determine if they provided a fitness benefit during interspecies interactions. Eleven total genes were studied, and we found that a majority impacted the fitness of S. mutans in various assays, highlighted by increased biomass of commensal streptococci in mixed-species biofilms. These results confirm a common, species-independent modification of S. mutans behaviors with oral commensal streptococci that emphasizes the need to further evaluate oral bacteria within multispecies settings.

Human saliva modifies growth, biofilm architecture, and competitive behaviors of oral streptococci

“…Recently, our group highlighted a repetitive DEG pattern for S. mutans during coculture growth compared with monoculture, including with S. oralis ( 14 ). To determine how saliva modified this pattern, we compared S. mutans DEGs during transition from monoculture to coculture growth with S. oralis in either TY- or TY-Saliva (i.e., DEGs from coculture in TY- vs DEGs from coculture in TY-Saliva).…”

“…Our group recently transcriptomically characterized coculture growth between S. mutans and several species of commensal streptococci ( 14 ). However, these experiments were carried out in our lab-based experimental medium, tryptone and yeast extract (TY-).…”

Human Saliva Modifies Growth, Biofilm Architecture and Competitive Behaviors of Oral Streptococci

“…Recently our group highlighted a repetitive DEG pattern for S. mutans in coculture with commensal streptococci that included S. oralis (14). We wanted to determine how coculture growth in medium containing saliva modified this pattern and the overall interaction between the species.…”

“…RNA was sequenced through SeqCenter with their 8 M Single Reads package applied to RNA from monocultures and their 16 M Single Reads package applied to RNA from cocultures. Delivered .FASTQ files were uploaded and analyzed through Galaxy (77) with a custom pipeline (14,78,79) that included FASTQ Groomer [v 1.1.5], FASTQ Quality Trimmer [v 1.1.5], mapping of reads to respective genome files with Bowtie2 [v 2.3.4.3] and htseq-count [v 0.9.1] on genome features from species-specific .GFF3 files that resulted in a .CSV file containing non-normalized reads counts. All read counts were combined into a single .CSV file and uploaded to Degust (80) and edgeR analysis performed to determine log2 fold change and false discovery rates (FDR) for all genome features.…”

Exploring the In Vitro Antibacterial Potential of Specific Probiotic Strains against Oral Pathogens

“…It forms a biofilm on tooth surfaces—the so-called dental plaque, one of the most common diseases worldwide. It has been also associated with extraoral pathologies, such as infective endocarditis or atherosclerosis [ 9 , 12 , 13 ].…”