"Biofilm, city of microbes" (1) was one of the defining reviews for me as a new post-doc, quite a while ago. It made me realize that my path forward as a microbiologist has to be in the context of microbial ecology. Microbes do not dwell alone, quite the contrary, they thrive when others are around, like to chat, share, work together and sometimes fight with neighboring species co-inhabiting the biofilm. My group is interested in these interspecies interactions that are ultimately responsible for species distribution in the developing biofilm and determine overall biofilm architecture. The species distribution inside the biofilm is also intimately linked to the ability of a biofilm to cause disease or as even more important, but vastly understudied, support health. Our area of research is the oral biofilm.

 We previously reported that two abundant and oral health associated species, Streptococcus sanguinis and Corynebacterium durum have a close relationship through the production of membrane vesicle and fatty acids leading to S. sanguinis chain elongation and overall increased fitness supporting their commensal state (2) and Fig 1.  

To further understand the relationship and define the molecular mechanisms that lead to the observed chain elongation phenotype, we performed global transcriptome analysis of the co-cultures to identify differentially expressed genes in S. sanguinis. Two operons caught our interest, the glp-operon encoding important genes for glycerol metabolism and the pil-operon responsible for type IV pilus formation on the surface of S. sanguinis.

Why is research into commensals and "molecular commensalism" important?