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The overall objective of this research is to develop methods to prevent the growth of
pathogenic and spoilage microorganisms in minimally preserved, brined, and fresh-cut
foods and optimizing safety, quality, and sensory attributes specifically through: <ol> <li> Development of fundamental knowledge of the biochemistry of bacterial adaptation to
acidified environments;
<li> Determination, through analysis of gene/protein expression
profiles, the responses to intrinsic and extrinsic stressors and, in particular, the
effect of oxygen imposed on pathogenic bacteria during production, processing, and
storage of acid and acidified foods;
<li> Development of data and its use for the
development of mechanistic models for growth, survival and inactivation of pathogens.</ol>
<p>The effect of common food acids and acid preservatives will be evaluated for their
relative ability to enhance killing of acid-tolerant food pathogens, particularly
Escherichia coli O157:H7, in the absence of oxygen and independent of pH. Work will
be carried out at biosafety level 2 (BSL-2) due to the organisms under investigation.</p>
<p> Selected acid/pathogen strain combinations will be analyzed using genetic and
biochemical analyses to determine the mechanisms by which acids are responsible for
killing E. coli and other pathogens. This information will be utilized to identify
common metabolic targets for the killing effects of acids and acid preservatives, as
well metabolic targets unique to particular acids. Since we have found that oxygen
increases the killing rates of acid-tolerant pathogens at low pH, similar
investigations will be done to determine the genetic and metabolic responses of acid-
tolerant pathogens to acids in the presence of molecular oxygen and oxygen radicals.
These results will be used to determine the mechanisms by which oxygen species
enhance killing of pathogens in acid and acidified foods. </p><p>
Data from genetic and
metabolic experiments will be used to develop mechanistic mathematical models and
validate the models that are developed in order to test hypotheses developed from
genetic and metabolic investigations of acid-killing and acid resistance of food
pathogens.</p>