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Biofilm formation occurs when free floating microorganisms attach themselves to a surface. They secrete extracellular polymers that provide a structural matrix and facilitate adhesion. Because biofilms protect the bacteria, they are often more resistant to traditional antimicrobial treatments, making them a serious health risk.〔Donlan, R. M. "Biofilm and Device-Associated Infections." ''Emerging Infectious Diseases'' 7.2 (2001)〕 For example, there are more than one million cases of catheter-associated urinary tract infections (CAUTI) reported each year, many of which can be attributed to biofilm-associated bacteria.〔Maki, D. and Tambyah, P. "Engineering Out the Risk for Infection with Urinary Catheters." ''Emerging Infectious Diseases'' 7.2 (2001)〕 Currently, there is a large sum of money and research aimed at the use of and protection against biofilms. == Composition of biofilm == Biofilms consist of microorganisms and their self-produced extracellular polymeric substances (EPS). A fully developed biofilm contains many layers including a matrix of EPS with vertical structures, and a conditioning film. Vertical structures of microorganisms sometimes take the form of towers or mushrooms, and are separated by interstitial spaces. Interstitial spaces allow the bulk of the biofilm to easily and rapidly take in nutrients from the surrounding liquid and move byproducts away from the biofilm. Formation of biofilms are rather complex, but can be generalized in four basic steps: deposition of the conditioning film, microbial (planktonic) attachment to the conditioning film, growth and bacterial colonization and finally biofilm formation. #Conditioning film: Conditioning films alter the surface properties of the substratum and allow microorganisms to adhere to the surface. For example, when sterile, medical implants are exposed to bodily fluids, proteins, polysaccharides, ions and various other components adhere to the surface and form a conditioning film which "invites" microorganisms that would otherwise be unable to attach to the original surface. #Adsorption and attachment: While the exact mechanism of microorganism attachment is still unknown, DLVO theory and thermodynamic interaction mechanisms have been used to help explain the initial microbial attachment. #Growth and colonization: Production of polysaccharides that anchor the bacteria to the surface allow colonies to grow. The growth process is the most significant step in biofilm accumulation when accounting for biofilm mass.〔Hjortsø, Martin A., and Joseph W. Roos. Cell Adhesion: Fundamentals and Biotechnological Applications. New York: M. Dekker, 1995. Print.〕 #Biofilm formation: A fully developed biofilm will contain an EPS matrix and vertical structures separated by interstitial spaces. Biofilms have a heterogeneous structure and are capable of mass internal transport.〔Lennox, J. "Biofilm Development." Biofilms: The Hypertextbook. Web. 1 May 2011. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Chemistry of biofilm prevention」の詳細全文を読む スポンサード リンク
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