Biofilm is a colony of microorganisms, primarily bacteria, that attaches to a surface and forms a sticky film. Biofilms have unique properties not found in unattached cells, including greater resistance to antibiotics. Biofilms may form on almost any surface exposed to bacteria and water, including parts of the human body. Familiar biofilms include the coating called plaque that builds up on teeth and the slimy material that clogs household drains.
When bacteria form a biofilm, they produce sugary, sticky molecules called exopolysaccharides. The exopolysaccharides help attach the bacterial cells both to the surface and to one another. The polysaccharide molecules also form a slimy protective layer that covers the cells. The layer of slime protects the bacteria from hazardous materials, from drying out, and from being eaten by bigger organisms. Strands of exopolysaccharides hold the bacterial cells at a distance from one another, enabling small water channels to form in the biofilm. The channels act as a primitive circulatory system, carrying nutrients (nourishing substances) and oxygen into the cells and taking waste products away.
A biofilm may consist of bacteria of the same species or of many different species. It may also include such microscopic organisms as algae, protozoans, and yeasts.
Some biofilms are beneficial. For example, biofilms on skin and mucous membranes (the moist tissues that line the nose, throat, and other structures) protect the body from harmful bacteria. Biofilms in the large intestine help break down foods and absorb nutrients. Water treatment plants may use biofilm bacteria to treat wastewater and sewage.
However, many biofilms create serious problems. Plaque on teeth causes tooth decay. People with implanted medical devices, such as heart valves and artificial knee and hip joints, can develop serious infections from biofilms growing on the devices. In patients with the disease cystic fibrosis, biofilms cause lung infections. In industry, biofilms can clog pipes and damage other equipment. They can contaminate surfaces of food processing plants, increasing the risk of food poisoning. Biofilms can even develop on ships’ hulls, slowing the ships’ movement.
Antibiotics and disinfectants usually cannot remove a biofilm once it has developed. For this reason, people try to control biofilms by preventing them from forming. In addition, genetic research may reveal the specific genes that lead to the formation of harmful biofilms, as well as ways of attacking these genes.
See also Bacteria .
