Ships that sail the seas foul to slime. What do we know about this universal fouling problem?
Firstly, we know that the marine industry is not alone in facing a slime challenge. As fouling control coatings researchers at AkzoNobel, we are interested in the drag consequences of biofilms (slime) on ships. Surgeons worry that biofilms on implanted medical devices can harbour pathogens, or that biofilms in chronic wounds result in long lasting infections. Biofilms in dairy plants can result in food spoilage. Accumulated biofilms in power plant cooling towers can drastically reduce heat exchange. Biofilms can reduce the cross-sectional area of pipes, resulting in drinking water transport inefficiencies or blockage of fuel lines. Dental biofilms lead to painful tooth decay and other health problems. And biofilms are even a potential problem in space, where they might act as hotbeds of microbially induced corrosion on long term installations like the International Space Station.
Whether marine, clinical, industrial or extra-terrestrial, biofilms are characterised by properties that give them superpowers of persistence which are especially vexing in industrial contexts. A biofilm is made of living microorganisms embedded in an extracellular polymeric matrix produced by some or all of the cells, and typically is adhered to an immersed surface. The microbial community diversity can range from biofilms dominated by only a few species of bacteria to highly diverse environmental biofilms that contain thousands of species of bacteria, microalgae, fungi, protozoa and other species all living in close association. The architecture, chemical composition and physical properties of biofilm matrices are likewise variable, reflecting the species that form the biofilm and the local environmental conditions such as local flow conditions. Finally, these diverse microbial systems can also respond to environmental change on timescales of minutes, hours, and days, modifying their biological, chemical, and physical properties.