35th Street Corvallis, Oregon 97333 Tong, Yongyi, and Bruce Lighthart.
Solar radiation has a lethal effect on natural populations of outdoor atmospheric bacteria.
Ambient heterogenic atmospheric bacteria were collected by impaction directly onto nutrient agar surfaces on clear sunny and cloudy days and at night. Bacterial survival was the least for the organisms collected at nightime and the greatest for those collected during clear sunny days. This result may be due to the inactivation of SR-sensitive bacterial populations by the ambient SR on clear days, and to a lesser extent on cloudy days, leaving only the relatively resistant populations. This does not occur at night when the SR-sensitive populations have not been reduced. The mixed bacterial species populations in the atmosphere do not appear to follow the Bunsen-Roscoe reciprocity law but integration of pure bacterial components of the mixed population that do follow the law, could explain the findings.