A biofilm can be said to be the community house of micro-organisms or maybe a microbial city. The term is generally used with respect to bacteria but biofilms can also be made my protozoans or yeast.Many free floating bacteria (planktonic forms) give up their nomadic existence and tend to aggregate in a place and live a sedentary lifestyle within a biofilm.
Biofilms can be formed on any surface as long as the bacteria sense that nutrients would be available to them. Initially it may attach to the surface with its pili. Later on, other bacteria may also come and attach themselves to the same surface. In this way a microcolony would be formed. Now as the number of inhabitants start increasing, the bacteria decide to fortify their dwelling place and hence secrete an exopolysaccharide (EPS). This exopolysaccharide builds up the matrix of the biofilm within which many bacteria may live.
A biofilm may comprise of the same species of bacteria or related species which may benefit each other in a symbiotic relationship. Also, the bacteria living together in this manner communicate with each other via quorum sensing. This involves small chemical messengers sent by one bacterium that affects the behaviour of the other bacteria around it. Also the bacteria utilize a different repertoire of genes when they are in a biofilm as compared to when they are free floating. Due to proximity there is also a high rate of horizontal gene transfer within the different species in a biofilm.
Since most biofilms are complex colonies made of many different micro-organisms even the structure of the polysaccharides that form the extracellular matrix of the biofilm tends to differ, sometimes even within the same biofilm. The biofilms maybe neutral in nature or polyanionic or polycationic. It has also been found that the polysaccharide which comprises the biofilm is very similar to what the planktonic cells secrete as an exopolysaccharide. Also, mutant cells which do not secrete EPS are also not capable of forming biofilms by themselves. However, in a mixed microbe setting this does not matter much because if one of the species cannot contribute to the matrix of the biofilm, the other species may do that work.
Living together in such a manner has its benefits. The EPS biofilm provides protection against antimicrobials. Due to this, biofilms are difficult to destroy by medicines. Also, since the antimicrobials cannot reach them, the bacteria also tend to be more resistant and as a consequence, more virulent.
It also is a strong protective measure from adverse environmental conditions.
However, even though biofilm formation most of the times is undesirable, it does have its uses. Biofilms have been harnessed in waste water treatment and bio remediation.
References:
http://mic.sgmjournals.org/content/147/1/3.full.pdf
http://jb.asm.org/content/182/10/2675.full.pdf+html
More reading:
http://www.hypertextbookshop.com/biofilmbook/v004/r003/contents/chapters/chapter001/section005/green/page001.html
Biofilms can be formed on any surface as long as the bacteria sense that nutrients would be available to them. Initially it may attach to the surface with its pili. Later on, other bacteria may also come and attach themselves to the same surface. In this way a microcolony would be formed. Now as the number of inhabitants start increasing, the bacteria decide to fortify their dwelling place and hence secrete an exopolysaccharide (EPS). This exopolysaccharide builds up the matrix of the biofilm within which many bacteria may live.
A biofilm may comprise of the same species of bacteria or related species which may benefit each other in a symbiotic relationship. Also, the bacteria living together in this manner communicate with each other via quorum sensing. This involves small chemical messengers sent by one bacterium that affects the behaviour of the other bacteria around it. Also the bacteria utilize a different repertoire of genes when they are in a biofilm as compared to when they are free floating. Due to proximity there is also a high rate of horizontal gene transfer within the different species in a biofilm.
Since most biofilms are complex colonies made of many different micro-organisms even the structure of the polysaccharides that form the extracellular matrix of the biofilm tends to differ, sometimes even within the same biofilm. The biofilms maybe neutral in nature or polyanionic or polycationic. It has also been found that the polysaccharide which comprises the biofilm is very similar to what the planktonic cells secrete as an exopolysaccharide. Also, mutant cells which do not secrete EPS are also not capable of forming biofilms by themselves. However, in a mixed microbe setting this does not matter much because if one of the species cannot contribute to the matrix of the biofilm, the other species may do that work.
Living together in such a manner has its benefits. The EPS biofilm provides protection against antimicrobials. Due to this, biofilms are difficult to destroy by medicines. Also, since the antimicrobials cannot reach them, the bacteria also tend to be more resistant and as a consequence, more virulent.
It also is a strong protective measure from adverse environmental conditions.
However, even though biofilm formation most of the times is undesirable, it does have its uses. Biofilms have been harnessed in waste water treatment and bio remediation.
References:
http://mic.sgmjournals.org/content/147/1/3.full.pdf
http://jb.asm.org/content/182/10/2675.full.pdf+html
More reading:
http://www.hypertextbookshop.com/biofilmbook/v004/r003/contents/chapters/chapter001/section005/green/page001.html
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