Bacteria created biofilms

This pioneering results [17] account for the first usage of bacteria-created biofilms in the preparation of optical devices and opened up a new trend in the multidisciplinary research toward exploiting natural structures as potential hosts for advanced devices. 

Microbial cells transported with the stream of fluid above the surface interact with conditioning films. Immediately after attachment, microorganisms initiate production of slimy adhesive substances, predominantly exopolysaccharides (EPS) that assist the formation of microcolonies and microbial films. EPS create bridges for microbial cells to the substratum and permit negatively charged bacteria to adhere to both negatively and positively charged surfaces. EPS may also control interfacial chemistry at the mineral/biofilm interface. 

Gradients of nutrients and oxygen in biofilms additionally promote high diversity, which may ultimately result in functional differences of the bacterial community in biofilms compared with free-floating bacteria. Additionally, increased species diversity may provide spatial and temporal niches not available within monocultures or may create microenvironments within the biofilm (Gieseke et al., 2001 Whiteley et al., 2001). These thoughts reinforce the need for community-level biofilm studies as opposed to monocultures. 

Production of differential aeration cell. A scatter of individual barnacles on a stainless steel surface creates oxygen concentration cells. The formation of biofilm generates several critical conditions for corrosion initiation. Uncovered areas will have free access to oxygen and act as cathodes, while the covered zones act as anodes. Underdeposit corrosion (crevice corrosion) or pitting can occur. Depending on the oxidizing capacity of the bacteria and the chloride ion concentration, the corrosion rate can be accelerated. However, the presence of a biofilm does not necessarily mean that there will always be a significant effect on corrosion. (Dexter)5... 

Woimd healing and infection is influenced by the relationship between the ability of bacteria to create a stable, prosperous community within a woimd environment and the ability of the host to control the bacterial community. Within a stable, climax biofilm commimity, interactions between aerobic and anerobic bacteria are likely to increase their net pathogenic effect, enhancing their potential to cause infection and delay healing. Chronic wounds are invariably polymicrobial, yet most research to date has focused on the role of specific potential pathogens in woimds (e.g., P. aeruginosa) rather than the effect of interactions between different species (Percival and Bowler, 2004). 

The formation of thick biofilms could in principle be beneficial if a compact film would uniformly cover a metal, preventing access of oxygen to the surface. However, biofilms usually do not form uniformly over a metal surface but usually in patches. Therefore they stimulate the formation of corrosion cells between covered and non-covered areas. The phenomenon is further enhanced if anaerobic conditions prevail at the metal surface in the areas covered by the biofUm, creating conditions for the development of anaerobic bacteria such as SRB that inhibit passivation. The following two examples illustrate the corrosive effect of microorganisms. 

Local corrosion of metals occurs during the formation of aeration or other concentration elements, which result as a consequence of settlement of microorganisms and build-up of colonies. As described in Sec. 4.3.3, the continuous growth of a colony may create conditions that make the proliferation of anaerobically growing bacteria possible, even in anaerated environment. A colony may be considered as a locally limited biofilm (Flemming and Geesey, 1991). 

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