title: The Microbiome of Ehrlichia-Infected and Uninfected Lone Star Ticks (Amblyomma americanum).
abstract: The Lone Star tick, Amblyomma americanum, transmits several bacterial pathogens including species of Anaplasma and Ehrlichia. Amblyomma americanum also hosts a number of non-pathogenic bacterial endosymbionts. Recent studies of other arthropod and insect vectors have documented that commensal microflora can influence transmission of vector-borne pathogens; however, little is known about tick microbiomes and their possible influence on tick-borne diseases. Our objective was to compare bacterial communities associated with A. americanum, comparing Anaplasma/Ehrlichia -infected and uninfected ticks. Field-collected questing specimens (n = 50) were used in the analyses, of which 17 were identified as Anaplasma/Ehrlichia infected based on PCR amplification and sequencing of groEL genes. Bacterial communities from each specimen were characterized using Illumina sequencing of 16S rRNA gene amplicon libraries. There was a broad range in diversity between samples, with inverse Simpson's Diversity indices ranging from 1.28-89.5. There were no statistical differences in the overall microbial community structure between PCR diagnosed Anaplasma/Ehrlichia-positive and negative ticks, but there were differences based on collection method (P < 0.05), collection site (P < 0.05), and sex (P < 0.1) suggesting that environmental factors may structure A. americanum microbiomes. Interestingly, there was not always agreement between Illumina sequencing and PCR diagnostics: Ehrlichia was identified in 16S rRNA gene libraries from three PCR-negative specimens; conversely, Ehrlichia was not found in libraries of six PCR-positive ticks. Illumina sequencing also helped identify co-infections, for example, one specimen had both Ehrlichia and Anaplasma. Other taxa of interest in these specimens included Coxiella, Borrelia, and Rickettsia. Identification of bacterial community differences between specimens of a single tick species from a single geographical site indicates that intra-species differences in microbiomes were not due solely to pathogen presence/absence, but may be also driven by vector life history factors, including environment, life stage, population structure, and host choice.
authors.affiliation: Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: R T
authors.initials: RT
authors.lastname: Trout Fryxell
authors.affiliation: Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: J M
authors.initials: JM
authors.lastname: DeBruyn
mesh_terms: D000709:Anaplasma; D000818:Animals; D004269:DNA, Bacterial / Q000032:analysis; D017753:Ecosystem; D004536:Ehrlichia; D005260:Female; D008297:Male; D064307:Microbiota; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013045:Species Specificity; D017282:Tick-Borne Diseases / Q000382:microbiology*; D013987:Ticks / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S