THE FACULTATIVE INTRACELLULAR PATHOGEN LISTERIA (L.) MONOCYTOGENES IS RESPONSIBLE FOR LISTERIOSIS, A RARE BUT SEVERE DISEASE IN HUMANS AND ANIMALS, WHICH IS ACQUIRED PRIMARILY THROUGH THE CONSUMPTION OF CONTAMINATED FOOD; PARTICULARLY "READY-TO-EAT FOOD" IS OF HIGH RISK. LISTERIOSIS PRIMARILY AFFECTS OLDER ADULTS, PREGNANT WOMEN, NEWBORNS, AND ADULTS WITH WEAKENED IMMUNE SYSTEMS. LISTERIOSIS CAN PRESENT IN DIFFERENT WAYS: IN OLDER ADULTS AND PEOPLE WITH IMMUNOCOMPROMISING CONDITIONS, SEPTICEMIA AND MENINGITIS ARE THE MOST COMMON CLINICAL PRESENTATIONS. PREGNANT WOMEN MAY EXPERIENCE A FEVER AND OTHER NON-SPECIFIC SYMPTOMS, FOLLOWED BY FETAL LOSS OR BACTEREMIA AND MENINGITIS IN THEIR NEWBORNS. IMMUNOCOMPETENT PEOPLE MAY EXPERIENCE ACUTE FEBRILE GASTROENTERITIS OR NO SYMPTOMS. ALTHOUGH THE INCIDENCE OF LISTERIOSIS IS RELATIVELY LOW WITH APPROX. 0.26 CASES PER 100,000 INDIVIDUALS, APPROX. 1600 ILLNESSES AND 260 DEATHS DUE TO LISTERIOSIS OCCUR ANNUALLY IN THE UNITED STATES. LISTERIOSIS ISCHARACTERIZED BY A HIGH MORTALITY RATE RANGING FROM 15 TO 30%. IN SPITE OF CURRENT FOOD SAFETY MEASURES IN THE FOOD INDUSTRY, LISTERIOSIS OUTBREAKS ARE CONTINUOUSLY OCCURRING. THE 2011 CANTALOUPE LISTERIOSIS OUTBREAK WITH 147 CASES AND 33 DEATHS WAS THE LARGEST LISTERIOSIS OUTBREAK IN THE US AFFECTING 28 STATES. THE ANNUAL COSTS OF L. MONOCYTOGENES IN THE US WAS ESTIMATED TO BE 2.3 TO 22 BILLION $. L. MONOCYTOGENES CAN SURVIVE AND GROW IN MULTIPLE NATURAL AND MAN-MADE HABITATS, SUCH AS SOIL, MARINE AND FRESH WATER, VEGETATION, SEWAGE, FOOD PROCESSING PLANTS, FARM ENVIRONMENTS, DOMESTIC AND WILD ANIMALS; THEREFORE, CONTROLLING L. MONOCYTOGENES IN FOOD PROCESSING ENVIRONMENTS IS A CONSIDERABLE CHALLENGE. PLASMIDS ARE KNOWN TO PROVIDE BENEFITS TO THEIR HOSTS ALLOWING BETTER ADAPTATION TO CHANGING ENVIRONMENTAL CONDITIONS. THE KNOWLEDGE ABOUT L. MONOCYTOGENES VIRULENCE AND SURVIVAL MECHANISMS IN FOOD AND FOOD PROCESSING ENVIRONMENTS IS LARGE, PARTICULARLY FOR CHROMOSOMALLY ENCODED MECHANISMS. IN CONTRAST, THE KNOWLEDGE ABOUT PLASMIDS AND THEIR FUNCTION IN L. MONOCYTOGENES IS STILL VERY LIMITED. THIS PROJECT AIMS TO ANALYZE THE CONTRIBUTION OF PLASMIDS (IN L. MONOCYTOGENES) TO SURVIVAL OF (THE PATHOGEN) LISTERIA MONOCYTOGENES IN FOOD AND FOOD PRODUCTION ENVIRONMENTS. WE PLAN TO: (1.) DETERMINE THE SURVIVAL OF PLASMID-CURED L. MONOCYTOGENES STRAINS UNDER VARIOUS STRESS CONDITIONS FOUND IN FOOD AND FOOD PRODUCTION ENVIRONMENTS, (2.) ANALYZE THE GENE EXPRESSION OF PLASMID-CARRYING L. MONOCYTOGENES STRAINS UNDER STRESS CONDITIONS FOUND IN (1.) TO IDENTIFY CANDIDATE GENES FOR FURTHER FUNCTIONAL CHARACTERIZATION, AND (3.) TO CHARACTERIZE THE CONTRIBUTION OF PLASMID STRESS RESPONSE CANDIDATE GENES BY EXPRESSION IN L. MONOCYTOGENES, AND (4.) TO PERFORM A LARGE SCALE SURVEY OF SEQUENCED L. MONOCYTOGENES STRAINS FOR THE PRESENCE AND GENETIC CONTENT OF PLASMIDS.UNDERSTANDING HOW PLASMIDS CONTRIBUTE TO SURVIVAL OF L. MONOCYTOGENES UNDER STRESS CONDITIONS IN FOOD AND FOOD PRODUCTIONENVIRONMENTS, WILL UNCOVER MOLECULAR MECHANISMS THAT REGULATE L. MONOCYTOGENES SURVIVAL. A BETTER UNDERSTANDING OF THESE MOLECULAR MECHANISMS IS THUS URGENTLY NEEDED TO INCREASE FOOD SAFETY AND TO BE ABLE TO DEVELOP BETTER CONTROL MECHANISMS AGAINST L. MONOCYTOGENES IN THE LONG-TERM.