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1. Biofilm

The investigation of bacterial biofilms is singularly more difficult than the investigation of planktonic bacteria. Unfortunately, bacterial biofilm investigation centres on the development of planktonic bacteria in laboratory cultures, a condition which has little relation with actual microbial environments. This has limited a global understanding of the interactions betweenbacteria. (Donlan, 2002; Thomas et al., 2006).
Just a tiny fraction of bacteria is found in planktonic or free flotation form, and bio-film bacteria are different from planktonic ones. It is said that 99% of all bacterial cells exist in biofilms quality and only 1% live in a planktonic state. (Sanclement et al., 2005; Palmer., 2006)
That bacteria adhere to surfaces has been recognized for severaldecades. Back in the 1970s, microbiologists stated that probably most of the bacteria in nature lived in a biofilms state; however, the therapy of most human infections continues based on the study of a minority of planktonic, free floating bacteria. Biofilms are created when free floating bacteria get attached to a surface, and then produce chemical signs in order to coordinate a differentiation andformation of structure, including the development of a polysaccharide protective layer. (Scott et al., 2006).
Bacteria can create conditions to form biofilms in almost any liquid environment. The solid-liquid interphase between a surface and aqueous medium (e.g. water, blood) supplies an ideal environment for the setting and growing of microorganisms. Therefore, biofilms are naturally located andpossible to find in practically every natural body of water in the world. (Sanderson et. al., 2006)
Bacterial biofilms represent an ancient prokaryotic survival strategy, due to the fact that the bacteria gain meaningful advantages by providing protection to the biofilms against environmental fluctuations of humidity, temperature and pH, as well as, concentrating nutrients and facilitating theelimination of waste. (Thomas et. al., 2006; Chole et al., 2003; Anderel et al., 2000).
The capacity to form biofilms seems not to be restricted to any specific group of microorganisms. At the present moment, it is considered that under appropriate environmental conditions most bacteria, no matter the species, can exist inside the biofilms attached to surfaces in a solid/liquid interphase.(Thomas et. al., 2006; Chole et. al., 2003; Anderl et al., 2000).
A biofilms is an assemblage of microbial cells that is irreversibly associated (not removed by gentle rinsing) with a surface and enclosed in a matrix of primarily polysaccharide material. (Donlan., 2002)
Van Leeuwenhoek, by using his simple light microscopes, was the first to describe the presence of microorganisms attached to dentalsurfaces; hence, he has been recognized as the discoverer of bacterial biofilms. (Donlan, 2002)
This line of investigation resurfaced in the 1970s when Characklis decided to study microbial silt in industrial water systems, getting to demonstrate their resistance to several disinfectants, among them chlorine. (Donlan, 2002)
Later, microbiologists hypothesized that biofilms could be theexplanation for the existence of mechanisms by which bacteria are adhered to living or inert surfaces. The presence of bacterial communities, embedded in a glycoprotein matrix joined to surfaces in contact with water, led them to this hypothesis. (Costerton et al., 1978)
Nevertheless, it was necessary to wait until the appearance of the electronic microscope to get a detailed examination of biofilms. Itallowed high-resolution photo-microscopy with significant advantages over the light microscope. In the last two decades a great part of the work done for the description of biofilms has been based on electronic microscopy. By this means we proceeded to examine biofilms in filters of waste water treatment plants, finding out they were composed of a multiplicity of bacteria. (Jones et al.,1969)...
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