Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/5/2012
Publication Date: 7/1/2012
Publication URL: http://handle.nal.usda.gov/10113/56596
Citation: Rounds, M.A., Crowder, C.D., Matthews, H.E., Philipson, C.A., Scoles, G.A., Eshoo, M.W. 2012. Identification of endosymbionts in ticks by broad-range polymerase chain reaction and electrospray ionization mass spectrometry. Applied and Environmental Microbiology. 49(4):843-850. Interpretive Summary: Ticks harbor a wide variety of microorganisms and some of these are transmissible and can cause disease both in humans and animals. Many tick species also contain bacterial endosymbionts that are not transmissible but instead are passed transovarially from one generation of ticks to the next. Many of these symbionts are very closely related to and difficult to distinguish from transmissible tick-borne pathogens. In addition, many of these intracellular bacteria are unique to specific tick populations or tick species, presumably due to isolation and genetic drift. The method described in this paper uses polymerase chain reaction amplification with several sets of broad spectrum primers, followed by electrospray ionization-mass spectrometry for identification of the PCR amplicons, to detect and identify a wide range of tick associated microorganisms including both pathogens and symbionts. Using this system endosymbiont genetic signatures have been characterized from a wide variety of tick species collected at various sites and of different stages and both sexes. The assay is able to simultaneously detect pathogens and closely related endosymbionts within the same tick DNA isolate as well as to identify ticks to species by characterizing their respective unique endosymbionts. Methods that can simultaneously detect and differentiate between tick-borne pathogens and tick symbionts can help us to improve our understanding of the epidemiology of tick-borne disease
Technical Abstract: Many organisms, such as insects, filarial nematodes, and ticks, contain heritable bacterial endosymbionts that are often closely related to transmissible tickborne pathogens. These intracellular bacteria are sometimes unique to the host species, presumably due to isolation and genetic drift. We used a polymerase chain reaction/electrospray ionization-mass spectrometry assay designed to detect a wide range of vectorborne microorganisms to characterize endosymbiont genetic signatures from Amblyomma americanum (L.), Amblyomma maculatum Koch, Dermacentor andersoni Stiles, Dermacentor occidentalis Marx, Dermacentor variabilis (Say), Ixodes scapularis Say, Ixodes pacificus Cooley & Kohls, Ixodes ricinus (L.), and Rhipicephalus sanguineus (Latreille) ticks collected at various sites and of different stages and both sexes. The assay combines the abilities to simultaneously detect pathogens and closely related endosymbionts and to identify tick species via characterization of their respective unique endosymbionts in a single test.