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Appl Environ Microbiol. 1989 July; 55(7): 1690-1694
Copyright © 1989, American Society for Microbiology. All Rights Reserved.
Department of Biological Sciences and Environmental Research Center, University of Nevada, Las Vegas, Nevada 89154
ABSTRACT
The survival after freezing of ice nucleation-active (INA) and genetically engineered non-INA strains of Pseudomonas syringae was compared. Each strain was applied to oat seedlings and allowed to colonize for 3 days, and the plants were subjected to various freezing temperatures. Plant leaves were harvested before and after freezing on two consecutive days, and bacterial populations were determined. Populations of the INA wild-type strain increased 15-fold in the 18 h after the oat plants incurred frost damage at 5 and 12°C. Plants colonized by the non-INA strain were undamaged at 5°C and exhibited no changes in population size after two freeze trials. As freezing temperatures were lowered (7, 9, and 12°C), oat plants colonized by the non-INA strain suffered increased frost damage concomitant with bacterial population increases following 18 h. At 12°C, both strains behaved identically. The data show a relationship between frost damage to plants and increased bacterial population size during the following 18 h, indicating a potential competitive advantage of INA strains of P. syringae over non-INA strains in mild freezing environments.
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