Listeria Biofilms

NON-TECHNICAL SUMMARY: Persistence of the foodborne pathogen L. MONOCYTOGENES in the food-processing environment is enhanced by its ability to form biofilms. The objectives of this project are: 1.) To define the process of LISTERIA MONOCYTOGENES biofilm development. 2.) To define structural elements and genes that are required for L. MONOCYTOGENES biofilm development.

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APPROACH: L. MONOCYTOGENES can form a single species biofilm on various surfaces that consist of large numbers of sessile bacteria. Our goal is to define the three-dimensional dynamics of biofilm formation using a flow-cell apparatus in combination with phase-contrast and confocal laser scanning microscopy. This analysis will reveal the pathway that leads to biofilm formation and will reveal the stages of biofilm development. It is also important to identify structural components, regulatory pathways and physiological activities that contribute to biofilm formation. To gain a better understanding of factors that contribute to biofilm formation, a genetic approach will used to identify genes essential for biofilm development (ebd). These genes will be characterized to define their functions and to evaluate their role in the process of biofilm formation.

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PROGRESS: 2003/09 TO 2007/08<BR>
OUTPUTS: Biofilms are surface associated communities of microorganisms. Many bacterial pathogens that cause foodborne illnesses form biofilms on food preparation and processing surfaces in the home and industrial settings. Listeria monocytogenes is a foodborne pathogen that has long been postulated to enter the food supply through direct and recurrent contamination due it ability to persist in biofilms. Activities include conducting and analyzing experiments related to biofilm formation. New genetic loci essential for biofilm formation were identified, mapped and characterized. The specific role that these genetic loci play in biofilm development were assessed using both a static culture approach and continuous feeding approach. It was found that both methods of evaluating biofilm formation are important because they represent alternative conditions experienced by bacteria in "real world" situations. All of the genetic loci characterized affected bacterial motility, which is behavior dependent upon biogenesis of a surface organelle called the flagellum. It was found that motility was important for initiation of biofilm formation under static culture conditions. In contrast, loss of flagellar motility enhanced biofilm formation under conditions where the continuous feeding was provided. The information from this research has been disseminated through presentations at public and scientific meetings, informal and formal university forums. In addition, presentations were given at local, national and international venues. Information on biofilm formation by foodborne pathogens related to this research were delivered to California country extension advisors at an on-campus forum and through the Western Institute of Food Safety and Security in meeting that included food industry representatives. Research presentations were presented annually at the San Francicsco Bay Area Bacterial Pathogenesis Symposium. At the national and international level, posters and oral presentation were delivered at the American Society for Microbiology 2007 Biofilms Meeting in Quebec, Canada and at the 7th International Food Science and Technology Conference (2008) in Wuxi, China. Dissemination of knowledge beyond the scientific audience occurs through multiple venues, including the publication of research overviews in the departmental quarterly new letter, through on site tours of the research laboratory and a research program overview to members of the the public that visit the university. On site tours have been delivered to university students, student's parent, international visitors, casual visitors to the university (members of the public) and stakeholders (representing industrial sectors related to food science). This project provided training to one Ph.D. student who graduated in August, 2007. Training was also provided to colleagues on campus related to the use of continuous feeding flow cells. This project is now a primary training focus for a new Ph.D. who is finishing her second year of a Ph.D. training program in Food Science. <BR>PARTICIPANTS: Glenn M. Young, Ph.D. - Associate Professor and Food Safety Microbiologist, AES - Principal Investigator. Responsible for the design and execution of the project. Briana M. Young, M.S. - Senior Research Associate - Responsible for conducting an analyzing results from experiments designed in cooperation with Dr. Young. Ms. Young also is responsible for the environmental safety training of all laboratory members. Tatsaporn Todhanakasem - Graduate student - Received training from Dr. Young for foodborne pathogen research. Responsible for conducting an analyzing results from experiments designed in cooperation with Dr. Young. This student finished her Ph.D. in August, 2007 and is now a faculty member in the School of Biotechnology, Assumption University, Bangkok, Thailand. Kullanart Tongkhao - Graduate student - Receiving training from Dr. Young for foodborne pathogen research. Responsible for conducting an analyzing results from experiments designed in cooperation with Dr. Young. <BR>TARGET AUDIENCES: The US and California agricultural, biotechnology, biomedical and food industries are target audiences for this research. Food safety and infectious disease research is a primary effort of these industries to maintain a safe food supply and to enhance human health.
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IMPACT: 2003/09 TO 2007/08<BR>
Many foodborne pathogens, including LISTERIA MONOCYTOGENES, persist on food processing equipment by forming a biofilm that can resist removal and sterilization procedures. Our results provide the first fundamental insight on the mechanisms used by the bacterium to form biofilms. We also discovered that, contrary to previously reported results by others, the loss of bacterial motility results in an enhancement of biofilm formation on abiotic surfaces. This a major insight into the biology of this foodborne pathogen. It was previously speculated that treatments that would inhibit bacterial motility might be useful for preventing biofilm formation. Our results call this idea into question, pointing to the importance of continuing our investigation. Therefore, the result of this fundamental knowledge help facilitate the development and testing of new measures to prevent this bacterium from entering the food processing environment and cause outbreaks of illness.