Biofilm is the terminology that is given to the collection or aggregation of microorganisms on a surface in which the cells adhere to each other. Generally, an extracellular polymeric substance (EPS) exists over the biofilm which embeds the biofilm within itself. This extracellular polymeric substance is mainly composed of proteins, polysaccharides and DNA. Biofilms have the potential to exist on living organisms and surfaces, and also on non-living surfaces.

Biofilms can be formed by the clustering of different types of microorganisms such as bacteria, protozoa, fungi, archaea, algae, etc. Some microorganisms of the same type form a biofilm exclusively for that type of microorganism.

Microorganisms can grow individually on their own and also in the form of a collection, as biofilms. These microorganisms experience a phenotypic behavior change when they shift from individual growth to biofilm growth.

Biofilms are created when microorganisms start attaching and clustering on a specific surface. Initially, the microorganisms are not attached to the surface very strongly and permanently and they can easily be removed. The initial microorganisms use the Van der Waals force to stay attached.  If the surface is not cleaned and the formation of the biofilm is not prevented, then eventually these microorganisms become more strongly and permanently attached. This happens when the microorganisms use the cell adhesion structures within them to bond with the surface.

When the first colonists of the microorganisms on the surface become attached permanently and strongly, they are then supportive for other microorganisms to attach very easily.  In this way, the clustering of the microbes continues. Some microorganisms do not have the ability to attach themselves to surfaces, however they could easily attach themselves to the already existing microorganisms.

If the formation and development of the biofilm is not stopped, the biofilm will continue to grow and increase in size. This clustering of microbes can become exceedingly antibiotic resistant.

There are five stages of the formation and development of biofilms;

  • Initial attachment

  • Irreversible attachment

  • Maturation I

  • Maturation II

  • Dispersion

The dispersion stage is when the biofilm spreads and starts colonizing other new surfaces as well.

Typically, biofilms exist on solid substrate surfaces which are also exposed to any aqueous solution. Nonetheless, biofilms can also sometimes exist on liquid surfaces as floating mats and can even be formed on leaves, principally in climates with high humidity. The formation of the biofilm starts from a size that is not visible to the naked eye, but if the formation and development is not stopped, then it can grow to a size which is easily visable.

The extracellular polymeric substance (EPS) effectively protect the microorganisms in the biofilm and also facilitates the communication between the microbes. The communication between the microorganisms is executed via biochemical signals. The EPS is strong enough to protect the microbes and sometimes the biofilms become fossilized.

Microorganisms floating freely in air and microorganisms in a biofilm possess different properties although they may be of the same species. These different properties are created by the dense and protected environment which the biofilm offers. Microorganisms of the biofilm become more resistant toward antibiotics and detergents. The extracellular polymeric substance and the outer layer of the cells prove to be very protective for these microbes. The resistance of a biofilm against antibiotics is a hundred times higher than the resistance of a free floating microorganism.

Biofilms in the human body can lead to various types of infections. The diseases and conditions in humans which are caused by biofilms include catheter infection, gingivitis, periodontal disease, formation of dental plaque, urinary tract infections, middle-ear infections and coating contact lenses.

Dental plaque is the formation of biofilm on the teeth. This biofilm comprises of bacteria in the oral cavity which can cause numerous dental problems and conditions. Dental plaque, if not removed, can turn into tartar, which is the harder form of plaque. Tartar becomes more difficult to remove and is more precarious than dental plaque.

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