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Interaction of Escherichia coli O157:H7 with Fresh Leafy Green Produce


The aim of this project is to elucidate the mechanism by which E. coli O157:H7 colonizes fresh produce and survives industrial decontamination. The results will be applicable to the development of an effective method of reducing the survival of this pathogen in fresh produce

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Environmental, ultrastructural, molecular, and bactericidal testing approaches will be applied in this project. Environmental studies will assess the role of temperature, pH, incubation time, gas requirements, plant age, and bacterial determinants on the colonization of leafy greens. Ultrastructural research will examine the structures produced by the bacteria that may be involved in bacterial adherence and colonization, such as pili and flagella. Molecular testing will focus on the introduction of specific bacterial effectors into the leaf to determine if they have a role in this phenomenon. Bactericidal testing will be used to assess various bactericidal agents that are non-toxic to humans to determine a more effective method of eliminating this organism from fresh produce.

Preliminary results indicate that E. coli O157:H7 can colonize the surface of spinach leaves using structures resembling flagella and can gain access to the internal leaf structure using the stomata. Colonization of the stomata may be the mechanism by which the E. coli can survive the industrial decontamination process. Further testing will focus on (1) identifying the pathogen's mechanism for manipulating the stomata, which aids internal colonization; (2) identifying the specific structures that play a role in leaf surface adherence; and (3) developing a method of sterilization that can be applied at the industrial level to eliminate E. coli O157:H7 from produce.

Giron, Jorge
University of Arizona
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