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Why Do Bugs Stick to What They Stick To


<p>The objective of this project is to carry out a comparative study of the effect of polymer phase transitions on bacterial adhesion.
<p>This will be achieved using a range of surface-coated or surface-grafted polymers with pre-determined phase transition characteristics.
<p>In this way the physical state of surfaces (otherwise chemically identical) could be assessed for their effect on the adsorption of the representative food pathogens Listeria monocytogenes, Bacillus cereus and Salmonella typhimurium.

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This research project aims to carry out a comparative study of the effect of polymer phase transitions on bacterial adhesion.

<p>The prevention of contamination caused by pathogenic microorganisms during manufacture, processing and packaging of food is of considerable importance to public health, and consequently a major issue for industry.
<p>In particular, there is increasing concern associated with the contamination arising from bacterial biofilms which develop on materials used during food manufacture. <p>These communities of bacteria, often embedded in a matrix of organic polymers exuded by the cells, can be extremely difficult to remove. Complete eradication of the pathogens is difficult, time consuming and expensive.

<p>In general, the formation of bacterial biofilms is believed to take place over at least three stages: a reversible adsorption step, primary adhesion of microorganisms to a surface, and colonisation.
<p>The rates of these processes vary widely depending on the environmental conditions and the type of microorganism but the adhesion and colonisation stages are considered to be relatively slow compared to the first step of cell adsorption.
<p>In principle, it should be possible to retard, if not prevent, the formation of biofilms on substrates by using materials to which bacteria cannot initially attach. Such a material or surface coating would be of considerable commercial interest.
<p>However, in practice, synthetic materials that are capable of preventing bacterial adsorption have proved rather elusive. Properties of the substrate such as hydrophobicity (repelling water), hydrophilicity (attracting water), steric hindrance (molecules which prevent bacteria attaching), roughness and the existence of a 'conditioning layer' at the surface are all thought to be important in the initial cell attachment process.

<p>The study will be concerned with two distinctly different phase transitions of polymers: <ol>
<li>the glass transition (Tg), which is property of the bulk polymer and describes the transition from a brittle, glassy material to a fluid-like or rubbery state and
<li>the transition occurring at the cloud point or lower critical solution temperature (LCST). The latter phenomenon is a property exhibited by certain water-soluble polymers, which form stable solutions at temperatures below the LCST, but precipitate rapidly above the LCST i.e. they show inverse solubility behaviour.</li>

<p>Find more about this project and other FSA food safety-related projects at the <a href="; target="_blank">Food Standards Agency Research webpage</a>.

Institute of Food Research, UK
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