Description

Microbial biofilms are defined as “a population of microorganisms that are concentrated at an interface (usually solid-liquid) and typically surrounded by an extracellular polymeric substance (EPS) matrix”. At one point biofilms were viewed as just simple passive assemblages of cells but technological advances and research has taken the initiative to understand biofilms and it has been revealed that biofilms are much more intricate then we believed. This review looks at the process of biofilm formation, the protective function of biofilms, and how biofilms can affect humans. The existence of biofilms dates back to about 3.2 – 3.4 billion years ago. Examination of these fossilized biofilms has revealed that biofilm formation is a key factor in the survival of prokaryotes in the natural environment.

Indication of biofilms were found in the fossil records in hydrothermal environments. Biofilms are characteristics of prokaryotic living fossils in the most ancient lineages of the phylogenetic tree in both the Archaea and Bacteria- the Korarchaeota and Aquificales. Environmental factors and the genome impact by what means biofilms form, but the stages of biofilm formation have stayed conserved throughout prokaryotes.

Within the article it states that “ In the evolution and adaptation it is likely that biofilms provided homeostasis in the face of fluctuating and harsh conditions of the primitive earth (extreme temperature, pH and exposure to ultraviolet (UV) light)”. This demonstrates biofilms ability to adapt to acertain environment over time. Each structure is unique and is dependent on the environment in which the growth occurs.

The formation of biofilm has been carefully studied and it was found that the formation proceeds in a five-step process. The 1^st and 2^nd steps are characterized by a loose association with the surface, followed by cell attachment to the surface. The 3^rd and 4^th step are categorized by the cell formation in microcolonies, followed by cell growth and maturation. The 5^th step is characterized by the biofilm regaining temporary motility, which allows for cells to be shed from the biofilm.

There are several methods as to how cells can detach and disperse from biofilms and they include swarming, clumping, and surface dispersal. In swarming the biofilm generates an outer wall and an inner region of microcolonies liquefies, which permits the cell to leave. Clumping dispersal permits for masses of cells to be unceasingly shed from the biofilm. Surface dispersal is the movement of biofilms, as a result of gliding/twitching motility or forces acting on the biofilm.

Biofilms are formed by prokaryotes for various reasons. Surfaces make available a space to dwell in and they offer some degree of steadiness in the growth environment and may have catalytic functions through localizing cells in the same vicinity. They also provide a form of defense from a wide range of environmental challenges such as UV exposure, metal toxicity, acid exposure, dehydration and salinity, phagocytosis and several antibiotics and antimicrobial agents. Three mechanisms have been offered to describe the overall resistance of biofilms to biocidal agents. To begin with is the barrier properties of the slime matrix. The second is the protective mechanism that could encompass the physiological state of biofilm organisms. While several antibiotics can easily penetrate the EPS, cells contained by the biofilm remain secure. Another mechanism of protection is due to the presence of a small subpopulation of bacteria known as persisters. These cells have yet to be cultured in a laboratory setting; they are believed to be the utmost resistant cells in the whole biofilm population.

Biofilm formation inside humans as a result of pathogenic bacteria has become a growing concern. In the early 1980s biofilms attached to medical devices were the first discovered and associated as the cause of clinical infection. The microorganisms most predominant in the medical equipment have been S.eperdermis, and S.aureus shadowed by P.aeruginosa and a bunch of other environmental bacteria. These microorganisms have found occasions to infect the host once they are compromised by intrusive medical procedures. The development of biofilms on medical implants has headed to the new infectious disease identified as chronic polymer-association infection. The most important characteristic dicuessed in this article is the adherence of staphylococci colonizing on medical implants is the ample quantity of EPS that wraps and shields cells from host resistances and antibiotics treatment.

Cystic Fibrosis is an autosomal recessive disease that is caused by mutations in the cystic fibrosis transmembrane conductance regulator gene that results in a dysfunctional electrolyte secretion and absorption. The primary site of morbidity is in the respiratory system. Because of cause and effect of CF the bacteria P.aeruginosa. P.aeruginosa now becomes a chronic infection. The bacteria begins to form a biofilm like structure in clusters surrounded by a dense matrix. The growth of the biofilms in CF produces a by-product of toxic nitrogen. Pulmonary colonization of the lower respiratory tract of the CF patients begins in infancy or early childhood, most commonly by S. aureus and Haemophilus influenza. However by adolescence and adulthood most CF patients have become colonized with P. aeruginosa. This shift is from the environment of the CF lung, which includes asialylated receptors on epithelial cells that facilitate pseudomonal attachment in addition to impaired mucociliary clearance. P.aeruginosa grows in biofilms in the CF lungs. It produces biofilm-like structures containing of clusters of bacteria enclosed by a dense matrix. Furthermore it has mucoid variants, which are categorized by over production of the exopolysaccharide alginate and a resistance to antibiotic therapy.

Biofilms were at one time viewed as being simple and not serving much of a purpose. However this article has exposed the significance biofilms play with prokaryotes and in what way there communication with the environment guarantees the survival of prokaryotes.

Bacterial Biofilms: From the Natural Environment to Infectious Diseases

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