Objectives are to: (1) identify mutations and other cellular damages that occur with excess near-ultraviolet radiation, and the molecular events involved in recovery from such damages; (2) with our current knowledge that near-UV induces synthesis of several Escherichia coli proteins regulated by the katF gene product, identify some of the details of the regulatory process; (3) isolate and characterize additional genes and gene products under katF regulation, and determine how each influences the cell in the recovery and mutational processes; (4) to determine whether there is a genetic relationship between "near-UV death," "starvation death" in katF mutants, and death in other known "starvation" mutants; (5) determine whether the katF regulon is unique, or whether it overlaps with other known regulons (e.g., heat shock, oxidative stress, anaerobic stress, superoxide stress); (6) compare the effects of near-UV at environmentally normal sunlight fluences with the near-UV fluences anticipated with ca. 15% depletion of stratospheric ozone ( a natural filter of solar UV), resulting in a projected 8-15% increase in 290-320 nm near-UV exposure for the entire surface biome. Excess near-UV could yield excess toxic oxygen species in cells. Reactive oxygen molecules have critical roles in both normal and abnormal cellular metabolism. In addition to solar near-UV, humans are constantly exposed to toxic near-UV by means of artificial illumination and reactive oxygen species via pollutants, disease and aging processes. Of particular significance to human health, near-UV may suppress the mammalian immune system. The experimental procedures that will be used are: (a) DNA base sequencing (to determine mutagenic specificity of near-UV); (b) two dimensional gel electrophoretic analysis (to identify unique proteins involved in recovery from near-UV stress); (c) construction of genetic fusions of promoters of candidate "near-UV response" genes with B- galactosidase structural gene; (d) construction of fusion of B- galactosidase promoter with katF structural gene for experiments involving regulation of candidate "recovery" genes; (e) analysis of results to assess importance of anticipated excess near-UV mutational and physiological activities of cells.