What is biofilm?
You may not be familiar with the term “biofilm” but you have certainly encountered biofilm on a regular basis. The plaque that forms on your teeth and causes tooth decay is one type of bacterial biofilm. The “gunk” that clogs your drains is also biofilm. If you have ever walked in a stream or river, you may have slipped on biofilm-coated rocks.
Biofilm forms when bacteria adhere to surfaces in moist environments by excreting a slimy, glue-like substance. Sites for biofilm formation include all kinds of surfaces: natural materials above and below ground, metals, plastics, medical implant materials—even plant and body tissue. Wherever you find a combination of moisture, nutrients and a surface, you are likely to find biofilm.
A biofilm community can be formed by a single bacterial species, but in nature biofilms almost always consist of rich mixtures of many species of bacteria, as well as fungi, algae, yeasts, protozoa, other microorganisms, debris and corrosion products. Over 500 bacterial species have been identified in typical dental plaque biofilms. Biofilms are held together by sugary molecular strands, collectively termed “extracellular polymeric substances” or “EPS.” The cells produce EPS and are held together by these strands, allowing them to develop complex three-dimensional, resilient, attached communities. Biofilms can be as thin as a few cell layers or many inches thick, depending on environmental conditions.
The study of biofilms has skyrocketed in recent years due to increased awareness of the pervasiveness and impact of biofilms on natural and industrial systems, as well as human health. Biofilms cost the U.S. literally billions of dollars every year in energy losses, equipment damage, product contamination and medical infections. But biofilms also offer huge potential for bioremediating hazardous waste sites, biofiltering municipal and industrial water and wastewater, and forming biobarriers to protect soil and groundwater from contamination. The complexity of biofilm activity and behavior requires research contributions from many disciplines such as biochemistry, engineering, mathematics and microbiology. New insights into the mysteries of biofilm are being published daily in a wide variety of science and engineering journals. We welcome you to the exploration of this rapidly expanding area of study.
Health and the human body
This may come as something of a shock to you, but about 90 percent of the cells in a human body are not human! In fact, the human body is heavily colonized by microbes that have found it a great place to live. We have communities of microbes living on all mucous surfaces and in our digestive tract, as well as on and in layers of our skin. For the most part we all get along; in fact, we depend on some of our gut microbes to help with digestion. Sometimes, however, the microbial load causes problems of infection. Dentists now understand, for instance, that dental caries (cavities) are the result of bacterial infection (and biofilms!). When the normal balance of microbial populations is upset or when our immune system is overwhelmed, we can have a real battle with microbial opportunists.
In the 1990s, as the biofilm concept was being introduced to the medical community, doctors began to make the connection between chronic, low-grade infections and the biofilm mode of growth. Dental professionals made the connection easily, as teeth could readily be scraped for microscopic examination. Internal cases of chronic infection have taken longer to prove, but testing has shown that many troublesome diseases have entrenched microbial populations at their core.
Between 1980 and 1992, infectious disease deaths increased by 58% (39% after age adjustment); the major contributors were HIV infection and AIDS, respiratory disease (primarily pneumonia), and bloodstream infection. Infectious diseases are still broadly endemic and maintain a large reservoir of agents that have the potential for rapid and widespread dissemination. Infectious diseases remain the leading cause of death worldwide and the third leading cause of death in the United States. In the United States, each year, approximately 25% of physician visits are attributable to infectious diseases, with direct and indirect costs estimated at more than $120 billion. Because recent research implicates biofilms as reservoirs for pathogenic organisms and sources of disease outbreaks, biotechnology measures are being created to control biofilms and/or sever the routes by which pathogenic organisms are transmitted from biofilms to susceptible people.
Manufactured materials and systems
Microbes like to grow on surfaces, whether natural or manmade. When it comes to industrial surfaces, bacteria are just doing “what comes naturally” by attaching to the surfaces with which they come into contact. However, their propensity for attachment causes many problems for a wide range of industries. Biofilm contamination and fouling occur in nearly every industrial water-based process, including water treatment and distribution, pulp and paper manufacturing and the operation of cooling towers. Biofilms are responsible for billions of dollars in lost industrial productivity, as well as product and capital equipment damage each year. Biofilms are notorious for causing pipe plugging, corrosion and water contamination.
Biofilms are implicated in otitis media, the most common acute ear infection in children in the U.S. Other diseases in which biofilms play a role include bacterial endocarditis (infection of the inner surface of the heart and its valves), cystic fibrosis (a chronic disorder resulting in increased susceptibility to serious lung infection), and Legionnaire’s disease (an acute respiratory infection resulting from the aspiration of clumps of Legionnella biofilms detached from air and water heating/cooling and distribution systems).
Biofilms may also be responsible for a wide variety of nosocomial (hospital-acquired) infections. Sources of biofilm-related infections can include the surfaces of catheters, medical implants, wound dressings, or other types of medical devices.
Biofilms avidly colonize many household surfaces, including toilets, sinks, counter tops, and cutting boards in the kitchen and bath. Poor disinfection practices and ineffective cleaning products may increase the incidence of illnesses associated with pathogenic organisms in the household environment.1
1Montana State University – Center for biofilm engineering (http://www.biofilm.montana.edu/biofilm-basics/index.html)