Bacteria are inherently much more resistant to hypotonic stresses than mamalian cells due to the protective effect of their peptidolglycan cell walls. I would imagine that biofilms are even more protected from such effects due to the protective extracellular polymeric substances that the microbes are embedded in. Biofilms are also highly prevalent in fresh water environments (rivers, lakes and water distribution systems) reflecting their high resilience.

Recently I investigated this for S.aureus. It occurs that staphylococcal cells embedded within the matrix don't need to do a lot, whereas planktonic staphylococcal cells increase production of osmoprotectants, like betaine-glycine. Check it out, maybe You find it interesting:http://www.ncbi.nlm.nih.gov/pubmed/24432320

Hi Christine,

Part of the nature of biofilms is that they produce their own micro-climate. The excretion of the glycocalyx traps organic and inorganic material around the cells. As a result within the biofilm a varity of pH and osmotic potentials are maintained. As a result biofilms tend to be resistant to osmotic shock at least for short periods. Prolonged exposure to a hypotonic (or hypertonic) solutions would ultimately affect the biofilm and cause cell lysis - in the short term my guess is that in a mature and established biofilm they would go largely unnoticed.

Years ago I did encounter what I believe was a problem with a biofilm contamination in a deionised water line at a blood transfusion facility. A Bacillus species (gram positive / spore forming) was repeatedly recovered from the water, even after flushing and disinfection. Ultimately the PVC water lines were replaced and the problem resolved. Of course Bacillus spores are very hardy, but for them to get into the deionised water supply there had to be vegetative cells growing.

hope this helps,

cheers,

Richard

Thanks for the answers.