Atmospheric dispersal of ice nucleation-active bacteria: the role of rain.

A strong net downward flux of bacteria was measured in a soybean field during two different rain events. The ice nucleation-activity and phytopathogenic host range of strains of Pseudomonas syringae isolated from rainwater and aerosols present during rain differed from those of the bacteria present on the soybeans. Bacteria that produce fluorescent pigments on an iron-deficient medium were 3-8%, 5-9%, and 81% of those isolated from aerosols during rain, from rain, and from the soybean leaves, respectively (...)