Seasonal population changes and characterization of ice-nucleating bacteria in farm fields of central alberta.

During the summer of 1983 in central Alberta, changes in the bacterial population inhabiting the leaves of field beans (Phaseolus vulgaris L.) and canola (Brassica napus L. Altex) were studied to determine if ice-nucleating bacteria were present on these plants. Three colony types (white, yellow, and peach-colored) were found on field beans and canola leaves. Approximately 25% of the isolates from the white colony group, which dominated the population, were ice-nucleating bacteria. No ice-nucleating bacteria were present on canola leaves. Out of a total of 76 ice-nucleating bacteria isolated, 5 representative cultures were characterized in detail and identified as Pseudomonas fluorescens. The fatty acid composition of these cultures was essentially identical to that of typical P. fluorescens cultures and was altered by varying the growth temperature from 10 to 30 degrees C.