An interesting talk I went to once discussed biofilms in public buildings such as hospitals and schools. The speaker had collected pipe samples from a variety of buildings and had analysed the scum growing inside for common disease-causing microbes. From memory, they had found Legionella in a fairly high proportion of these films. The conclusion is less that public building water is dirty and more that one should expect old buildings to have biofilms growing in their pipes. Biofilms, I have learned, are an issue in all sorts of industries where things get wet – for example, they contaminate medical equipment and increase barnacle colonisation of ships. Biofilms are annoying for me personally because the design of my shower means they form readily in the drain filter. Yet another reason I prefer short hair.

But what are biofilms, and why do they form? ‘Biofilm’ is a rather broad name for accumulations of microbes on surfaces. You’ve certainly come across them on your teeth, in your pluming, on wet rocks, in ponds or water trays in the garden. Nature abhors a vacuum and any moist environment with a sneeze worth of nutrient is open for colonisation. Biofilms can be complex multi-species systems with different niches depending on relative location. A pond of water in the sun, for example, would have microbes that need light at the surface and microbes that prefer dark further down.

From a scientific point of view, I’m interested in biofilms that occur in severely acidified ponds. Sometimes they are the only thing that can survive. What is it about them that enables this activity? How can they maintain their biochemical processes when the liquid they’re in is actively trying to dissolve them? Are they actively killed if pH increases, or are they merely outcompeted by better adapted microbes? We don’t know, but it’ll be fun to find out.

*There’s a joke to be made about biofilms and biopics but I just haven’t got there yet.