Biofilm

In detail

Where a surface stays wet, bacteria attach to it and secrete a matrix of sugars and proteins that binds them together and to the surface. That structure is a biofilm, and it behaves very differently from the same organisms suspended in water. The matrix physically limits how far a disinfectant penetrates, the organisms deeper in it are metabolically slower and less susceptible, and the film regenerates from survivors — which is why a drain, a washing-machine seal, a toothbrush holder or a shower hose that has been treated smells clean for days and then does not. The practical rule that follows is the important one: biofilm is removed mechanically, not chemically. A brush, hot detergent solution and physical contact do more than any product poured in and left, because the objective is to break the matrix off the surface rather than to kill through it. Two familiar cases follow the same pattern. The pink film in a shower or on a pet bowl is a biofilm-forming bacterium, and wiping removes it while spraying does not. And a washing machine's door seal harbours a film that a hot maintenance wash reduces but a wipe with detergent removes.

Why

• Silicone sealant is explained by Biofilm
• Bath sealant is explained by Biofilm
• Sink waste is explained by Biofilm
• Mould fungi is explained by Biofilm
• Washing machine microbiota is explained by Biofilm
• Kitchen sponge microbiota is explained by Biofilm
• Enzymatic drain treatment is explained by Biofilm