title: Genetic Diversity of Tick-Borne Rickettsial Pathogens; Insights Gained from Distant Strains.
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 pathogenAnaplasma marginaleinfects cattle in tropical and subtropical regions worldwide, including Australia. Genomic analysis of North AmericanA. marginalestrains 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 twoA. marginalestrains. The low diversity between these phenotypically distinct bacteria presents a unique opportunity to identify the genetic determinants of virulence and transmission.
authors.affiliation: 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.
authors.forename: Sebastián Aguilar
authors.initials: SA
authors.lastname: Pierlé
authors.affiliation: National Institute of Genomic Medicine, Computational Genomics Lab, Mexico City 14610, Mexico.
authors.forename: Ivan Imaz
authors.initials: II
authors.lastname: Rosshandler
authors.affiliation: The University of Queensland, Queensland Alliance for Agriculture & Food Innovation, St. Lucia, Queensland 4072, Australia.
authors.forename: Ammielle Akim
authors.initials: AA
authors.lastname: Kerudin
authors.affiliation: Queensland Department of Agriculture, Fisheries & Forestry, Tick Fever Centre, Wacol, Queensland 4076, Australia.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Sambono
authors.affiliation: The University of Queensland, Queensland Alliance for Agriculture & Food Innovation, St. Lucia, Queensland 4072, Australia.
authors.forename: Ala
authors.initials: A
authors.lastname: Lew-Tabor
authors.affiliation: Queensland Department of Agriculture, Fisheries & Forestry, Tick Fever Centre, Wacol, Queensland 4076, Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Rolls
authors.affiliation: National Institute of Genomic Medicine, Computational Genomics Lab, Mexico City 14610, Mexico.
authors.forename: Claudia
authors.initials: C
authors.lastname: Rangel-Escareño
authors.affiliation: 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.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Brayton
keywords: Anaplasma; Rickettsiales; SNPs; comparative genomics; intracellular bacteria