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United States Department of Agriculture

Agricultural Research Service

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Research Project: An in Vivo Negative Selection Screen to Identify Genes and Gene Families Required for Tick Colonization

Location: Animal Diseases Research

Project Number: 5348-32000-033-02
Project Type: Reimbursable

Start Date: Mar 15, 2011
End Date: Feb 28, 2014

Objective:
Identify metabolic and other functional pathways, genes and gene families required for tick colonization. Specific aim 1: Using Dermacentor andersoni ticks for negative selection, screen pools of Francisella tularensis subsp. novicida mutants to identify those mutants that have reduced fitness in the midgut or salivary glands. Specific aim 2: Verify the phenotype of a subset of the F. novicida mutants with reduced fitness in the midgut or salivary glands using dual infection experiments.

Approach:
A variety of intracellular bacterial pathogens of both humans and animals are transmitted by ticks and include members of the genus Anaplasma, Ehrlichia, and Rickettsia. Not only are the molecular mechanisms by which these pathogens are able to colonize the tick largely unknown. But, identification of these mechanisms is difficult, if not impossible, as the techniques required for genetic manipulation of this group of pathogen are in the early stages of development. In contrast to this limitation for tick-borne bacterial pathogens, exploitation of genomic sequence data through mutant library screens has allowed for relatively rapid identification of genes required for specific functions in a broad array of bacterial pathogens. Similarly, a transposon mutant library of Francisella tularensis subsp. novicida has been developed and used to negatively select and identify genes required for pulmonary and systemic infection in mice. We have determined that F. novicida readily colonizes D. andersoni in a manner similar to other tick borne pathogens, including A. marginale. Through a negative selection screen and high throughput sequencing, we propose to use this mutant library to identify genes required for tick colonization.

Last Modified: 8/27/2014
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