Survival of ice nucleation-active and genetically engineered inactive strains of Pseudomonas syringae

The survival of ice nucleation-active (INA) and genetically engineered non-INA strains of Pseudomonas syringae was compared under starvation and freezing conditions. In starvation experiments, both strains displayed similar survival curves and recovery from starvation was nearly identical for the two strains. In freezing experiments, oat seedlings colonized by each strain were subjected to freezing temperatures. Populations of the INA strain increased 15-fold in the 18 hours after oat plants incurred frost damage at {dollar}-{dollar}5 and {dollar}-{dollar}12{dollar}\sp\circ{dollar}C. Plants colonized by the non-INA strain were undamaged at {dollar}-{dollar}5{dollar}\sp\circ{dollar}C and exhibited no changes in population size. As temperatures were lowered, plants colonized by the non-INA strain suffered increased frost damage concomitant with bacterial population increases. At {dollar}-{dollar}12{dollar}\sp\circ{dollar}C, both strains behaved identically. The data show a relationship between frost damage to plants and subsequent increased bacterial population size, indicating a potential competitive advantage for INA strains of P. syringae in mild freezing environments