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Genetic Diversity of Tick-Borne Rickettsial Pathogens; Insights Gained from Distant Strains
Program in Genomics, Department of Veterinary Microbiology and Pathology, Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA 99164-7040, USA
National Institute of Genomic Medicine, Computational Genomics Lab, Mexico City 14610, Mexico
The University of Queensland, Queensland Alliance for Agriculture & Food Innovation, St. Lucia, Queensland 4072, Australia
Queensland Department of Agriculture, Fisheries & Forestry, Tick Fever Centre, Wacol, Queensland 4076, Australia
* Author to whom correspondence should be addressed.
Received: 8 November 2013; in revised form: 27 December 2013 / Accepted: 7 January 2014 / Published: 14 January 2014
Abstract: The ability to capture genetic variation with unprecedented resolution improves our understanding of bacterial populations and their ability to cause disease. The goal of the pathogenomics era is to define genetic diversity that results in disease. Despite the economic losses caused by vector-borne bacteria in the Order Rickettsiales, little is known about the genetic variants responsible for observed phenotypes. The tick-transmitted rickettsial pathogen Anaplasma marginale infects cattle in tropical and subtropical regions worldwide, including Australia. Genomic analysis of North American A. marginale strains reveals a closed core genome defined by high levels of Single Nucleotide Polymorphisms (SNPs). Here we report the first genome sequences and comparative analysis for Australian strains that differ in virulence and transmissibility. A list of genetic differences that segregate with phenotype was evaluated for the ability to distinguish the attenuated strain from virulent field strains. Phylogenetic analyses of the Australian strains revealed a marked evolutionary distance from all previously sequenced strains. SNP analysis showed a strikingly reduced genetic diversity between these strains, with the smallest number of SNPs detected between any two A. marginale strains. The low diversity between these phenotypically distinct bacteria presents a unique opportunity to identify the genetic determinants of virulence and transmission.
Keywords: intracellular bacteria; comparative genomics; SNPs; Rickettsiales; Anaplasma
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Pierlé, S.A.; Imaz-Rosshandler, I.; Kerudin, A.A.; Sambono, J.; Lew-Tabor, A.; Rolls, P.; Rangel-Escareño, C.; Brayton, K.A. Genetic Diversity of Tick-Borne Rickettsial Pathogens; Insights Gained from Distant Strains. Pathogens 2014, 3, 57-72.
Pierlé SA, Imaz-Rosshandler I, Kerudin AA, Sambono J, Lew-Tabor A, Rolls P, Rangel-Escareño C, Brayton KA. Genetic Diversity of Tick-Borne Rickettsial Pathogens; Insights Gained from Distant Strains. Pathogens. 2014; 3(1):57-72.
Pierlé, Sebastián A.; Imaz-Rosshandler, Ivan; Kerudin, Ammielle A.; Sambono, Jacqueline; Lew-Tabor, Ala; Rolls, Peter; Rangel-Escareño, Claudia; Brayton, Kelly A. 2014. "Genetic Diversity of Tick-Borne Rickettsial Pathogens; Insights Gained from Distant Strains." Pathogens 3, no. 1: 57-72.