Purpose: The objective of this study was to determine influence of constituents of water, soil, or manure on colonization of E. coli O157:H7 on plant tissue by plant defense response.
Methods: Arabidopsis thaliana ecotype Columbia (Col-0) wild-type and Arabidopsis BGL2-GUS transgenic plants were dip inoculated with E. coli O157:H7 ATCC 43895, grown or exposed to water, soil or manure, at a concentration of approximately 108 CFU/ml in water for 30 s. At 0, 1, 3, and 5 days post challenge wild-type Arabidopsis plants were harvested and the populations were determined by plating the homogenates on TSA supplemented with appropriate antibiotics. At day 5 post inoculation, GUS activities of BGL2-GUS transgenic plants were determined to monitor plant defense responses.
Results: On day 5 post inoculation, the population of E. coli O157:H7 grown in LB alone, LB supplemented with soil or manure on Arabidopsis wild-type plant was 5.06, 5.51, and 6.36 CFU/g, respectively. E. coli O157:H7 exposed to water, soil, or manure (6.98, 6.76, and 7.10 CFU/g, respectively) showed greater colonization on the wild-type plant compared to control (non-exposed) E. coli O157:H7 (5.06 CFU/g). E. coli O157:H7 cultured in LB exhibited 2-fold greater GUS activity compared with cells grown in LB with soil or manure extracts. E. coli O157:H7 exposed to water or manure showed 3-fold less GUS activity compared with non-exposed cells.
Significance: This study demonstrated that physiological changes of E. coli O157:H7 occurring following exposure to water, soil, or manure may influence plant defense response, and consequently impact colonization of the plant.