In order to identify novel traits involved in epiphytic colonization, a technique for the rapid identification of bacterial mutants with quantitatively different population sizes in a natural habitat based on measurements of ice nucleation activity was developed. The threshold freezing temperatures of leaves harboring different numbers of cells of ice nucleation-active Pseudomonas syringae B728a differed substantially. While few leaves containing less than about 106 cells per g (fresh weight) froze at assay temperatures of -2.75°C or higher, nearly all leaves froze at these temperatures when population sizes of this strain increased to about 107 cells per g (fresh weight). Presumptive epiphytic fitness mutants could readily be identified as strains which initiated freezing in fewer leaves than did other strains within a given experiment. Most Tn5-induced mutants of strain B728a which conferred a low frequency of ice nucleation on inoculated bean leaves generally had a smaller population size than the parental strain at the time of the leaf freezing assay. The leaf freezing assay was capable of differentiating samples which varied by approximately three- to fivefold in mean bacterial population size.
CITATION STYLE
Lindow, S. E. (1993). Novel method for identifying bacterial mutants with reduced epiphytic fitness. Applied and Environmental Microbiology, 59(5), 1586–1592. https://doi.org/10.1128/aem.59.5.1586-1592.1993
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