THE PROPOSED STUDIES ARE INTENDED TO PROVIDE DATA SHOWING THE FEASIBILITY OF DEVELOPING A BACTERIA-LASER SYSTEM FOR DETECTION AND MEASURING THE TOXIC RESPONSE FROM CHEMICAL EXPOSURE AT LEVELS FAILING TO PRODUCE ACUTE SYMPTOMS, BUT POSSIBLY CAUSING

THE PROPOSED STUDIES ARE INTENDED TO PROVIDE DATA SHOWING THE FEASIBILITY OF DEVELOPING A BACTERIA-LASER SYSTEM FOR DETECTION AND MEASURING THE TOXIC RESPONSE FROM CHEMICAL EXPOSURE AT LEVELS FAILING TO PRODUCE ACUTE SYMPTOMS, BUT POSSIBLY CAUSING DETECTABLE DAMAGE YEARS LATER. A BATTERY OF ISOGENIC "BACILLUS SUBTILIS" STRAINS WITH MUTATIONS IN VARIOUS DNA OR CHROMOSOMAL REPAIR STEPS, AND CAPABLE OF IDENTIFYING SPECIFIAL CHEMICAL CLASSES, WILL BE USED TO SCREEN HIGH PRIORITY POLLUTANT CHEMICALS FOR THEIR CYTOTOXICITY AND DNA-DAMAGING EFFECTS. FROM THE BATTERY OF MORE THAN 20 MUTANTS, A SMALLER SET CONSISTING OF STRAINSSHOWN TO DETECT THE GREATEST NUMBER OF SUBSTANCES AND TO RESPOND WITH THE HIGHEST LEVEL OF SPECIFICITY, WILL BE SELECTED FOR USE IN A DIFFERENTIAL LIGHT SCATTERING (DLS) ASSAY. THE SYSTEM WILL USE A MONOCHROMATIC LASER SOURCE TO ILLUMINATE THE "B. SUBTILIS" (BACTERIAL) CELL SUSPENSIONSIN A CLEAR CURVETTE. AN ARRAY OF DETECTOR ELEMENTS ARRANGEDSO THAT THEY WILL RECEIVE THE SCATTERED LIGHT AT A SERIES OF DISCRETE ANGLES WILL MEASURE DLS INTENSITY. SINCE EACH ELEMENT WILL MEASURE THE SCATTERED LIGHT INTENSITY AT A DIFFERENT ANGLE RELATIVE TO THE INCIDENT BEAM, A UNIQUE DLS PATTERN WILL BE GENERATED, BASED ON THE SIZE AND SHAPE CHARACTERISTICS OF CELLS IN THE SUSPENSION. SINCE CHANGES SUCH AS CELL SHRINKAGE, ENLARGEMENT, DIVISION OR LYSIS WILL GENERATE UNIQUE DLS PATTERN DEVIATIONS, A TOXICITY RESPONSE WILL BE DETECTED WITHIN THE SPAN OF A SINGLE GENERATION (APPROXIMATELY 60 MIN). FOR EACH SAMPLE ANALYZED BY THIS PROCEDURE, COMPOUND-SPECIFIC DOSE RESPONSES WILL BE VALIDATED BY BACTERIAL LIQUID AND PLATE DNA-DAMAGING/ CYTOTOXICITY ASSAYS AND BY CONVENTIONAL PROCEDURES OF ANALYTICAL CHEMISTRY. PHASE I R&D IS EXPECTED TO LEAD TO DEVELOPMENT OF A PORTABLE INSTRUMENT FOR RAPIDLY ASSAYING AND TENTATIVELY IDENTIFYING A WIDE RANGE OF TOXIC AGENTS IN THE ENVIRONMENT; USEFUL IN MONITORING WATER SUPPLIES, WORKERS EXPOSED TO POTENTIALLY HAZARDOUS CHEMICALS, AIR PARTICULATES OR LEACHATES FROM TOXIC WASTE SITES AND THE TOXICITY OF CHEMICALS FROM MANY ENVIRONMENTAL SOURCES.