Colorado State University Extension
SafeFood Rapid Response Network
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HOW AND WHY BACTERIA COMMUNICATE IN FOOD ENVIRONMENTS
By Yohan Yoon and John N. Sofos, Department of Animal Sciences, Colorado State University, Fall, 2006
The discovery that bacteria are able to communicate with each other has changed our perceptions of the many single celled organisms that inhabit our world. However, instead of using English or some other language, bacterial cells communicate among themselves using low-molecular-weight compounds (called autoinducers) through what is known as "quorum sensing," a cell density-dependent signaling system (1).
Quorum sensing enables bacteria to coordinate their behavior. Interestingly, in order to avoid detection by the host immune system, pathogenic bacteria do not use quorum sensing at low levels of cell density, but only when they reach a level sufficient to overcome the host immune system (2). Quorum sensing molecules (autoinducers) have been grouped into four different types and may be involved in such bacterial activities as virulence, bioluminescence, protein production, and biofilm formation (1).
Recently, quorum sensing of bacteria found in food environments has been suggested as a potential target to control food quality and safety. If we understand how bacteria use quorum sensing to communicate and organize themselves, we can develop systems that interfere with or block these signaling systems, thus preventing the bacteria from being dangerous. Jay et al. (3) has suggested that food spoilage and biofilm formation may be caused by quorum sensing of dominant bacteria in fresh meat during low storage temperature (5-7oC). Others (4, 5) have reported that bacterial spoilage in various foods may be associated with quorum sensing. Major pathogenic bacteria such as Escherichia coli O157:H7, Salmonella, and Campylobacter species, have been found to produce autoinducer-2 (AI-2) molecules in foods such as milk, chicken broth, and brucella broth at different storage temperatures (6). Overall, bacteria may use quorum sensing for their growth, survival, and virulence in food environments (6). While different bacterial species use different signaling molecules to communicate, there is some evidence that interspecies communication (known as cross talk) can also occur.
In complex food environments, the role of the quorum sensing and factors affecting quorum sensing molecule production are not very clear. Thus, we (Drs. Yoon and Sofos) have conducted studies to examine quorum sensing of major foodborne pathogenic bacteria such as E. coli O157:H7 and Salmonella, and the environmental factors affecting quorum sensing by these pathogens in food environments or related conditions. Additional research is needed to examine the resistance of foodborne pathogenic bacteria against antimicrobials, and their ability to survive under the human immune system.
Sources:
- Smith, J. L., P. M. Fratamico, and J. S. Novak. 2004. J. Food Prot. 67:1053-1070.
- Bauer, W. D., and J. B. Robinson. 2002. 13:234-237.
- Jay, J. M., J. P. Vilai, and M. E. Hughes. 2003. Int. J. Food Microbiol. 81:105-111.
- Christensen, A. B., K. Riedel, L. Eberl, L. R. Flodgaard, S. Molin, L. Gram, and M. Givskov. 2003. Microbiology 149:471-483.
- Rasch, M., J. B. Andersen, K. F. Nielsen, L. R. Flodgaard, H. Christensen, M. Givskov, and L. Gram. 2005. Appl. Environ. Microbiol. 71:3321-3330.
- Cloak, O. M., B. T. Solow, C. E. Briggs, C-Y. Chen, and P. M. Fratamico. 2002. Appl. Environ. Microbiol. 68:4666-4671.
