Factors Affecting Colonization of Plants by Human Pathogenic Bacteria

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The surfaces of plants are normally colonized by large numbers of bacteria,called epiphytes, which include plant pathogens, other saprophytic and beneficial bacteria as well as human pathogenic bacteria such as E.coli and Salmonella. </p>
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Preliminary studies have shown that while E.coli and Salmonella strains can grow on moist plants, they are hypersensitive to the stress of dry leaf surfaces compared to other bacteria found on plants, indicating that stress tolerance is a determining factor in their epiphytic colonization. </p>
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We will determine the differences among successful plant colonists and human pathogens in such intrinsic stress tolerance by measuring their growth and survival after inoculation onto plants under a variety of controlled conditions as well as in the field. </p>
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This information will enable the extensive background information on other leaf surface colonists to be extrapolated to predict the behavior of human pathogens on plants and to devise better methods to avoid or eradicate human pathogens on plants. </p>
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While epiphytes can occur as solitary cells, the majority of the population often occurs in relatively large aggregates which can contribute to the survival of stresses on leaves and successful immigration to a leaf.</p>
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We will determine the extent to which the survival of human pathogens on leaves is dependent on the numbers of indigenous bacteria present on a leaf and, at small scales, will study the role of bacterial aggregates in survival and proliferation of such strains using microscopic techniques to quantify and evaluate the viability of bacteria on leaves.</p>