How do Biofilms Work?

Biofilms are defined as groups of microorganisms in which cells adhere to each other on a given surface. Often, these cells are adhering to each other and to the surface within a matrix composed of extracellular polymeric substance. This matrix is secreted by the microorganisms that reside within the microfilm. The extra-polymeric surface from which a given biofilm is comprised is often referred to colloquially as slime and is composed primarily of DNA, proteins, and polysaccharides that have been secreted from the cells within the biofilm. Biofilms can form and adhere to both living and non-living surfaces and are often prevalent under conditions in which bacterial growth is favorable. Typically, biofilms are formed in response to certain environmental conditions and cells which are within biofilms are usually considered to be undergoing a different type of growth than those that are not forming biofilms (even when the two are of the same species).

The initial formation of biofilms begins with microorganisms attaching to a given surface. The first members of a colony to attach to a surface usually attach through weak and reversible adhesion techniques. If they are not removed quickly, they begin to anchor themselves more strongly to that surface through the use of specialized structures such as pili, which are used for adhesion. Not all species of bacteria are capable of forming biofilms. Those species that are capable, however, use biofilms to perform specialized tasks or in order to increase their chances of survival in hostile environments. Once biofilms have formed a more strong attachment to a given surface, they begin to mature and to excrete more and more extracellular components as needed. Eventually, they begin a process of dispersal in order to spread themselves out and to establish new colonies.

Biofilms have a very complex method of operation. Some have been found to contain water channels in order to better disperse nutrients and signal molecules to the microorganisms that are found within them. The bacteria that are found within a given biofilm have different properties than their free living compatriots, even among the same species. The protective and specialized environment that is provided by the biofilm allows increased resistance to environmental hazards and to hostile chemicals such as detergents or antibiotics.

In addition to environmental survival, biofilms can play important roles in avoiding the immune systems of hosts (in the case of pathogenic microorganisms). Biofilms have been found in infections of catheter sites, urinary tract infections, infections of the inner ear, and gum and tooth infections. In addition, they have been found as a coating on contact lenses and are the primary cause of the formation of dental plaque. Because of the ability to contain excreted proteins and to contain and disperse signaling molecules, biofilms can play an important role in the ability of bacteria and other microorganisms survive through modification of their internal processes in response to threats or hostile environments. It is this ability that is the basis for the issues caused to immune function when biofilms are formed within the body. Biofilms have been found to have the ability to harden to the point of almost becoming fossilized while still containing living cells capable of reproduction and dispersal.

Biofilms are a method that bacteria and other microorganisms have at their disposal in order to better survive hostile environments. Through adhesion to other cells and to living or inert environmental surfaces, these microorganisms are able to excrete extracellular components that aid them in survival. Through an increased ability to move nutrients and signaling molecules around in environments and to communicate in a more specialized manner with each other, cells within biofilms are better able to evade hostile environmental conditions and immune responses. Not all biofilms, however, pose a threat to humans. Often, biofilms are simply found where bacteria or other microorganisms happen to be growing, and pose no threat to either humans that encounter them or the environment as a whole.

Written by : Alexander Maness, United States (M.S. in Biotechnology )

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Edited by: Rajesh Bihani ( Find me on Google+ )

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