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United States Department of Agriculture

Agricultural Research Service

Title: Sequestration and Enhanced Survival of Salmonella Enterica in Vesicles Released by a Soil-Borne Species of TETRAHYMENA.SURFACES.

Authors
item Brandl, Maria
item Rosenthal, Benjamin
item Haxo, Aileen
item Berk, Sharon - TENN.TECH.UNIV.COOKVILLE

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 6, 2004
Publication Date: March 1, 2005
Citation: Brandl, M., Rosenthal, B.M., Haxo, A.F., Berk, S.G. 2005. Sequestration and enhanced survival of salmonella enterica in vesicles released by a soil-borne species of tetrahymena.surfaces. Applied and Environmental Microbiology.71(3).1562-1569

Interpretive Summary: Protozoa are an integral part of most microbial consortia and are ubiquitous in nature, particularly in environments where water is present. Many species of protozoa feed on bacteria, which they ingest by phagocytosis and sequester within food vacuoles. We have examined the interaction of Salmonella enterica serovar Thompson with a soil-borne isolate of Tetrahymena. During incubation with S. Thompson, Tetrahymena released a large number of vesicles containing viable S. Thompson cells. In comparison, grazing on Listeria monocytogenes cells resulted in their digestion. A higher proportion of S. Thompson cells remained viable when enclosed in vesicles than when free in solution. Sequestration in vesicles provided also greater protection from low concentrations of calcium hypochlorite. Thus, the release of this human pathogen from Tetrahymena in high-density clusters enclosed in a membrane may have important implications for public health.

Technical Abstract: The interaction of Salmonella enterica serovar Thompson with a soil-borne isolate of Tetrahymena was examined using S. Thompson cells labeled with the green fluorescent protein. The bacteria were mixed in solution with cells of Tetrahymena at several ratios. During incubation with S. Thompson, Tetrahymena released a large number of vesicles containing green fluorescent S. Thompson cells. In comparison, grazing on Listeria monocytogenes cells resulted in their digestion and thus, the infrequent release of this pathogen in vesicles. The number of S. Thompson cells per vesicle increased significantly as the initial ratio of S. Thompson to Tetrahymena cells increased from 500:1 to 5000:1. The density of S. Thompson was as high as 50 cells per vesicle. Staining with propidium iodide revealed that a significantly higher proportion of S. Thompson cells remained viable when enclosed in vesicles than when free in solution. Enhanced survival rates were observed in vesicles that were secreted by both starved and unstarved Tetrahymena cells. Sequestration in vesicles provided also greater protection from low concentrations of calcium hypochlorite. Thus, the release of this human pathogen from Tetrahymena in high-density clusters enclosed in a membrane may have important implications for public health.

Last Modified: 12/20/2014
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