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United States Department of Agriculture

Agricultural Research Service

Title: Production of Autoinducer-2 in Salmonella Enterica Serovar Thompson Contributes to Its Fitness in Chickens But Not on Cilantro Plant Leaf Surfaces

Authors
item BRANDL, MARIA
item MILLER, WILLIAM
item BATES, ANNE
item Mandrell, Robert

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 22, 2004
Publication Date: May 3, 2005
Citation: Brandl, M., Miller, W.G., Bates, A.H., Mandrell, R.E. 2005. Production of autoinducer-2 in salmonella enterica serovar thompson contributes to its fitness in chickens but not on cilantro plant leaf surfaces. Applied and Environmental Microbiology. 71(5):2653-2662.

Interpretive Summary: Food-borne illness caused by Salmonella enterica has been linked traditionally to poultry products, but is associated increasingly with fresh fruits and vegetables. We have investigated the role of signaling via autoinducer-2 (AI-2) in the ability of S. enterica serovar Thompson to colonize the chicken intestine and the cilantro phyllosphere. A mutant of S. Thompson that is defective in AI-2 production was constructed by insertional mutagenesis of luxS. The population size of the S. Thompson parental strain was significantly higher than that of its LuxS- mutant in the intestine, spleen, and droppings of chicks, 12 days after their oral inoculation with the strains in a ratio of 1:1. In contrast, no significant difference in the population dynamics of the parental and LuxS- strain was observed after their inoculation singly or in mixtures onto cilantro plants.

Technical Abstract: We have investigated the role of signaling via autoinducer-2 (AI-2) in the ability of S. enterica serovar Thompson to colonize the chicken intestine and the cilantro phyllosphere. A mutant of S. Thompson that is defective in AI-2 production was constructed by insertional mutagenesis of luxS. Twelve days after their co-inoculation, the population size of the S. Thompson parental strain was significantly higher than that of its LuxS- mutant in the intestine, spleen, and droppings of chicks. No significant difference in the population dynamics of the parental and LuxS- strain was observed after their inoculation singly or in mixtures onto cilantro plants. Digital image analysis revealed that 70% of S. Thompson cells were present in large aggregates on cilantro leaves, but that the frequency distributions of the size of aggregates formed by the parental strain and the LuxS- mutant were not significantly different. Carbon utilization profiles indicated that the AI-2-producing strain utilized a variety of amino and organic acids more efficiently than its LuxS- mutant, but that most sugars were utilized similarly in both strains. Thus, inherent differences in the nutrients available to S. enterica in the phyllosphere and in the chicken intestine may underlie the differential contribution of AI-2 synthesis to the fitness of S. enterica in these environments.

Last Modified: 8/19/2014