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GOALS: This research reconciles consumer needs for "fresh-like" natural foods with their requirements for safety and minimal processing. As a rule, these desires are contradictory. However, the membranes that surround bacteria and spores (dormant, very resistant bodies formed by some bacteria) may be the "soft underbelly" that can be targeted for improved microbial safety. By combining basic studies on spore membranes with their destruction by high pressure processing (HPP, a non-thermal destruction method that leaves food in their raw-like state) this research should translate into improved safety and food quality. <P>
OBJECTIVES: <OL> <LI> Determine the membrane fluidity of spores from various bacterial species and compare them with the known fluidities of vegetative cells. <LI> Demonstrate the relationship among high pressure, membrane fluidity and spore lethality. <LI> Elucidate the relationship among HPP, membrane permeabilization (demonstrated by leakage of spore constituents) and spore lethality. </OL> EXPECTED OUTPUTS: The outputs of this project are research that establishes translational knowledge that will improve food safety. Findings will be published in peer reviewed journals.
NON-TECHNICAL SUMMARY: The microbiological safety of food is an issue of great importance to the state of New Jersey, the nation, and the world. This is reflected in its increased status as an NIFA priority area. Foodborne microbial pathogens account for an estimated 76 million cases of foodborne illness each year, which include up to 5,000 deaths. The estimated cost to the United States from foodborne illnesses associated with known pathogens is between $6.5 - $34.9 billion. This project serves as an "umbrella" for general research on the role of membranes in bacterial resistance to control agents. This project extends the methodology of the previous version of this Hatch Project (Mechanisms and food safety applications for antimicrobial proteins from lactic acid bacteria) to the study of spores and new techniques for their control. Parodoxically, consumers expect a maximum amount of safety yet also demand foods that are minimally processed. High Pressure Processing is a technique that can preserve fresh quality and assure food safety, if it could kill spores (the most resistant form of bacterial life). This project improves high pressure processing through manipulation of spore membranes. Thes results will initially be disseminated in publications, but ultimately adopted by food processors.
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APPROACH: A general overview of methodologies specific to each objective is given below: Overview of Objective 1. Membrane rigidity of spores is determined experimentally using DPH anisotropy. We have used a similar approach to demonstrate in real-time that the rigidity of L. monocytogenes cells increases as temperature decreases (Badaoui Najjar et al. 2007). Overview of Objective 2. Two strategies for manipulating spore fluidity include sporulation at different temperatures, which alters pressure sensitivity (Rasco 1998), or growing cultures in the presence of fatty acids with varied chain length, or 2-methyl butyric acid (a precursor of branched chain fatty acid synthesis). The Montville Laboratory has perfected this procedure to alter the membrane fluidity of Listeria monocytogenes cells (Badaoui Najjar 2009). Overview of Objective 3. Membrane permeabilization plays a critical role in spores for two reasons. First, it allows leakage of DPA, which stabilizes spore DNA and proteins against lethal forces. Second, permeabilization allows nutrients and energy sources into the spore so that it can commence the metabolism that leads to differentiation into a vegetative cell. Whether this permeabilization occurs prior to, during, or after germination is unknown. To answer these questions, we determine whether release is due to membrane poration (e.g. channel opening) or disruption.