Can bacteria in a biofilm sense and respond to mechanical inputs?

Recent work, from our group and others, has shown that bacteria can sense and respond to mechanical cues when they are in the single-cell state. We have also shown that the response to mechanical cues is linked to the production of cyclic-di-GMP (c-di-GMP), an intracellular signal that controls the transition of bacteria from the single-cell state to the biofilm state. Biofilms are communities of aggregated, interacting bacteria that resist antibiotics and the immune system and as a result cause most chronic, intractable bacterial infection. However, whether bacteria can respond to mechanical cues once they are part of a biofilm is not known and, to our knowledge, has not been investigated. If they are capable of such response, this could have implications for how biofilms respond to mechanically dynamic environments. To elucidate this, we want to examine two types of mechanical cues – deforming stress on a biofilm, and changes in biofilm elasticity. We use small (~millimeter-sized) hydrogels encapsulating bacteria to act as model biofilms. This allows us either to apply osmotic pressure to change the bulk volume of the bacteria-containing gel with the bacteria in situ or to controllably vary the elastic modulus of the encapsulating material.