Biofilms

BIOFILMS

Biofilms are microcolonies of one or more species of bacteria or fungi typically growing adherent to a biotic or abiotic surface. Biofilms form to allow bacteria to maintain themselves in a niche of their choosing rather than being washed away by the shear force of running water in the natural environment or the movement of body fluids and mucins in the body. Biofilms provide a more energy-efficient means of growth, capturing nutrients as they flow past and easily expelling waste. They also provide a more secure environment for sustainability, making it difficult for phagocytes, found both in nature and as part of the immune system, to eradicate the biofilm. Also, as a biofilm, bacteria and fungi are less susceptible to antimicrobials, allowing them to be more tolerant than their planktonic brethren to antibiotics found in nature and those used clinically. A cartoon of the biofilm life cycle of bacteria is shown in Figure 8.1. In the centre of the figure bacteria exist in a mature biofilm that may be formed from many species, as in a consortium formed on the face of a rock in a stream or those found in the mouth, as part of our dental plaque. Chemical signals regulate the interactions between members of the biofilm just as hormones regulate the cells of our body. For example, under specific stress conditions appropriate signalling may lead to an increase in phenotypic diversity within the biofilm to accommodate the stress or these signals may cause bacteria to revert to their more motile planktonic phenotype and leave the biofilm to establish new microcolonies that will give rise to a mature biofilm.