An official website of the United States government.
<OL> <LI> Fabricate representative lineage I and II reference microarrays and systematically probe genome diversity among 100 strains representing known genetic diversity of lineage I, II, and Ill. <LI> Determine the extent of the alterations that are unique to each lineage or which have interesting patterns of distribution <LI> Determine the phenotypic impact of lineage or serotype-specific alterations in genes potentially related to virulence or physiological characteristics by making knock out mutations in isogenic strains.
DNA microarrays will be fabricated from shotgun libraries of representative serotype 4b and serotype 1/2a strains. The arrays will then be used to probe genome diversity of a strain set representing the diversity of the three L. monocytogenes lineages. Lineage- and serotype-specific genome alterations will be mined using a combination of clustering algorithms and data sorting algorithms. Lineage-specific genes will be tested for function in virulence and adaptive responses by constructing isogenic strains and comparing their phenotypes in the mouse model, cell culture invasion assays, and physiological assays.
<p>
Listeria monocytogenes is a foodborne pathogen with robust physiological characteristics that can be highly virulent in humans, particularly in individuals with compromised cellular immunity. The organism is widely distributed in nature and can enter the food supply at the preand post-harvest levels. At least thirteen serotypes of L. monocytogenes have been identified and are distributed among three different evolutionary lineages of the species. Three of the thirteen serotypes, 4b, 112a, and 112b, are responsible for causing nearly 90% of human cases of listeriosis, suggesting that there may be quantitative differences in the ability of the different serotypes to cause disease in humans or to be transmitted to humans through contaminated food. To better understand virulence and ecological characteristics of the different serotypes, this project will use DNA microarray and genetic analysis to identify differences in genome content and to examine the phenotypic characteristics conferred by lineage- or serotype-specific genes