Microstructure and mechanical properties of in situ Streptococcus mutans biofilms

Insight into live microbial biofilm microstructure and mechanical properties and their interactions with the underlying substrate can lead to the development of new remedial strategies and/or materials. Here we report mechanical properties of dental pathogenic Streptococcus mutans biofilms, grown on a polystyrene-coated plate of a shear rheometer in physiologically relevant conditions, precisely controlled in a custom built bioreactor. In situ measurements demonstrated the importance of microstructure and composition of extracellular polymeric substances on the biofilm modulus. The biofilms behave like a weak gel with storage moduli higher than loss moduli. The simple but robust experimental technique presented here can easily be extended to other biofilm-material systems.