P3-38 Influence of Constituents of Water, Soil or Manure on Colonization of Escherichia coli O157:H7 on Plant by Differential Induction of Plant Defense

Wednesday, July 25, 2012
Exhibit Hall (Rhode Island Convention Center)
Seungwook Seo, Rutgers University, New Brunswick, NJ
Karl Matthews, Rutgers University, New Brunswick, NJ
Introduction: Contaminated irrigation water, soil, or manure has been considered potential contamination sources of fresh produce on the farm.  Physiological changes may occur in E. coli O157:H7 growing in or exposed to water, soil, or manure influencing plant colonization by differential induction of plant defense response.

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.