Quorum Sensing in Biofilms_ Why Bacteria Behave the Way They Do - IFT

Quorum Sensing in Biofilms_ Why Bacteria Behave the Way They Do - IFT

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Human pathogens form biofilms on food and food contact surfaces, thereby enhancing their ability to survive harsh environments, resist antimicrobial treatments, and persist in the food processing environment. January 1, 2009 First published in Journal of Food Science . January/February 2009. 74(1): R24–R37. doi: 10.1111/j.1750-3841.2008.01022.x. ( Download PDF version ) Introduction Even though food microbiologists often conduct experiments using planktonic cells, which are nonadherent bacteria growing as individual cells in liquid culture, biofilms are more likely to be a concern in the food industry. Human pathogens form biofilms on food and food contact surfaces, thereby enhancing their ability to survive harsh environments, resist antimicrobial treatments, and persist in the food processing environment. Normally, bacteria form complex bacterial communities that are closely associated with abiotic and biotic surfaces. These bacterial communities, known as biofilms, are adherent to a surface, an interface, or to each other. Biofilms may cause persistent low-level contamination of foods, and the presence of foodborne pathogens in a biofilm could cause food safety concerns. Cells in biofilms have been shown to detach and inoculate model food systems (Midelet and Carpentier 2004). Improvements in cleaning and sanitization have helped to reduce the persistence of these bacteria, which are more resistant to physical processes and chemical agents than their free-floating (planktonic) counterparts. In a previous Scientific Status Summary, Zottola (1994) asked whether biofilms were "a new problem for the food industry." Since that time, much has been done to understand biofilms and how to eliminate them. This Scientific Status Summary reviews the most recent research performed to understand biofilms and how to eliminate them. It begins with a basic tutorial on biofilms, explaining what they are and how they develop, and progresses to the purposeful mechanism of unified interaction that bacteria use to benefit each other: quorum sensing. The article then explains how quorum sensing processes allow bacteria to display a unified response advantageous to the population by facilitating tolerance to stress and providing access to nutrients and more favorable environmental niches. Finally, the article explores ways to prevent quorum sensing from occurring, thereby inhibiting the growth of biofilms, which may retard spoilage and benefit food production and safety. Overview of Biofilms Biofilms on surfaces have a characteristic structure consisting of microcolonies enclosed in a hydrated matrix of microbially produced proteins, nucleic acids, and polysaccharides. In this complex biofilm network, the cells act less as individual entities and more as a collective living system, often with channels to deliver water and nutrients to the cells at the inner portion of the biofilm. Biofilm organisms are significantly more resistant to environmental stresses or microbially deleterious substances (such as antibiotics and biocides) than planktonic cells. Biofilm cells present on infected tissues or medical devices are less susceptible to host immune responses than
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