BACTERIAL PLANT PATHOGENS RESULT IN CROP DEATH AND LOSS OF ARABLE LAND. RALSTONIA SOLANACEARUM, WHICH CAUSES BACTERIAL WILT IN A WIDE RANGE OF ECONOMICALLY AND NUTRITIONALLY RELEVANT CROPS, CAN PERSIST IN WATER AND SOIL IN THE ABSENCE OF A HOST, LIMITING FUTURE PRODUCTION IN INFESTED SOIL. FURTHER, THIS PATHOGEN CAN BE CARRIED ASYMPTOMATICALLY IN ORNAMENTAL PLANTS THAT ARE IMPORTED COMMERCIALLY, REPRESENTING A THREAT FOR THE INTRODUCTION OF SELECT AGENT STRAIN OF THIS PATHOGEN INTO THE US. DUE TO EXTRAORDINARY GENETIC DIVERSITY WITHIN THE RALSTONIA SOLANACEARUM SPECIES, DEVELOPING UNIVERSALLY RESISTANT PLANT LINES IS CHALLENGING, HOWEVER BASIC RESEARCH ON PATHOGEN-HOST INTERACTION HAS LED TO EFFECT PATHOGEN MANAGEMENT STRATEGIES THAT LIMIT DISEASE OUTBREAK. MANY MOTILE SOIL-DWELLING BACTERIA, INCLUDING RALSTONIA SOLANACEARUM, USE A SWIMMING BEHAVIOR CALLED CHEMOTAXIS TO MOVE TOWARD ATTRACTANT (AND AWAY FROM REPELLENT) CHEMICAL SOURCES. CHEMICALS EXUDED FROM PLANT ROOTS ACT AS ATTRACTANTS THAT ARE SPECIFICALLY SENSED BY BACTERIA, ALLOWING THEM TO FIND AND COLONIZE ROOTS IN THE SOIL. THE PATHOGEN PREFERENTIALLY MOVES TOWARDS HOST PLANT ROOTS OVER NONHOST PLANT ROOTS. IMPORTANTLY, MUTANTS OF RALSTONIA SOLANACEARUM THAT ARE NOT CHEMOTACTIC ARE UNABLE TO COLONIZE HOST PLANTS FROM THE SOIL MAKING CHEMOTAXIS AN INTERESTING TARGET FOR PATHOGEN CONTROL.CHEMOTAXIS IS DRIVEN BY DOZENS OF PROTEIN RECEPTORS ON THE BACTERIAL SURFACE THAT EACH RECOGNIZE A UNIQUE SUITE OF CHEMICAL ATTRACTANTS. USING INNOVATIVE GENETIC TECHNIQUES, WE AIM TO IDENTIFY RECEPTORS AND CHEMICAL SIGNALS SENSED BY RALSTONIA SOLANACEARUM THAT ALLOW THEM TO LOCATE AND INFECT HOST ROOTS (TOMATO, MELON, AND NEW GUINEA IMPATIENS). IN THIS STUDY, WE WILL COMPARE THE CHEMOTAXIS OF TWO STRAINS, ONE WITH A BROAD HOST RANGE (KNOWN TO INFECT TOMATO, MELON AND NEW GUINEA IMPATIENS) AND ONE WITH A NARROW HOST RANGE (ONLY KNOWN TO INFECT TOMATO). WE EXPECT TO IDENTIFY RECEPTORS THAT BROADLY RECOGNIZE PLANT ROOTS AND THAT RECOGNIZE HOST SPECIFIC SIGNALS. FURTHER, WE AIM TO IDENTIFY THE ROLE THESE RECEPTORS PLAY IN PATHOGENIC FITNESS OF RALSTONIA SOLANACAERUM AND HOW DISRUPTION OF THESE RECEPTORS AFFECTS THE ABILITY OF THE BACTERIA TO INFECT PLANTS. IN THE LONG TERM, THIS RESEARCH WILL GENERATE TARGETS AND METHODS FOR BIOLOGICAL AND CHEMICAL CONTROL OF THIS ECONOMICALLY DEVASTATING PATHOGEN, WHICH WILL PROTECT CROPS FROM INFECTION AND POTENTIALLY RESTORE INFECTED SOIL.