Background Information

The term biofilm is so new to science that it may not yet appear in your textbook. A biofilm is a layer consisting of various combinations of many different organisms, (frequently, bacteria.) The common factor among these organisms is that they grow together in an aqueous (water) environment attached (adhered) to a solid surface, or substrate, forming a film.

Living together, the members of the biofilm form a community of individual organisms of different species. Biofilms can form on almost any surface that is submerged in nonsterile water. The organisms of the community cooperate and interact with each other and the local environment. These complex relationships form a small ecosystem. Microbiologists have traditionally studied microorganisms grown in pure culture as a single species. In the natural world, microorganisms often grow as biofilms of more than one species.

Biofilm formation has evolved as an adaptation by the individual members of the community as they struggle to survive. The microorganisms within the biofilm produce a sticky glue-like material, or polysaccharide, that attaches them to the substrate. This material makes a biofilm slimy. Once attached, the bacteria interacting as a dynamic system compete with other organisms for nutrients found at the interface where the substrate and water meet.

Biofilm formation also serves a protective function for the members of its community. Microorganisms on the inside of the biofilm are often safe from predators, antibiotics, and biocides. Think of a biofilm as a sort of “microenvironment” or “microhabitat” that gives its living inhabitants a survival advantage.

Dental plaque was among the first groups of biofilms to be studied. Teeth provide a hard surface on which biofilms can attach themselves. Saliva and the remains of food we eat are both sources of nutrients for the bacteria that contribute to the formation of dental plaque and associated peridontal diseases.

Biofilms are found everywhere, including such extreme environments as the hot springs of Yellowstone National Park and the glaciers of the Antarctic. They can corrode pipes and the hulls of ships and contaminate processed foods. Biofilms grow on the porcelain surface of toilet bowls, wood siding, shower tiles, plastics, and wooden cutting boards. Biofilms are everywhere!

Because biofilms can also grow on surfaces inside other organisms they can potentially grow on anything that is inserted into the body. This includes such medical devices as catheters used for antibiotic therapy and chemotherapy, blood transfusions, and intravenous feedings. They can also grow on body implants and prosthetic devices and within the tissue of the upper respiratory tract, the gastrointestinal tract (GI), or the urinary tract. Biofilms also grow on contact lenses, mascara brushes, eye care solutions, and artificial fingernails.

Not all biofilms are harmful. Some biofilms are part of the normal flora inside our bodies and others help our bodies produce vitamins. In various ecosystems, biofilms are part of the food chain, facilitating the decomposition of dead organisms and the recycling of nutrients.

Biofilms are also used in the field of biotechnology. Two examples include the addition of certain biofilms in cattle feed to prevent disease, and their use to break down toxic wastes in the water purification process. A new research area known as bioprospecting has developed from the use of biofilms in biotechnology.

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