SOME FACTORS AFFECTING THE AIRBORNE SURVIVAL OF BACTERIA OUTDOORS

Airborne survival of two pseudomonads and a reference strain of Escher ichia coli (strain MRE 162) was studied outdoors using a modified micr othread technique. When cells of E. coli were suspended as clusters, s urvival was much greater than single cells, particularly outdoors. Cul ture age had a highly significant effect on survival of Pseudomonas ma ltophila with survival of 24 h cultures being more than 100-fold highe r than 48 h cultures. Survival of Pseudomonas fluorescens was variable and depended also upon the method of culture. Survival of E. coli and Ps. maltophila was studied at three locations differing in air qualit y and was found to be significantly reduced outdoors, particularly whe n held in direct daylight. Outdoor survival was not significantly diff erent at the three locations but was reduced at increasing temperature s. There was no apparent effect of wind direction or air quality. Resu lts are discussed with reference to the release of genetically-modifie d micro-organisms.