Seasonal Population Changes and Characterization of Ice-Nucleating Bacteria in Farm Fields of Central Alberta

Abstract

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°C.