Localization and Visualization of aCoxiella-Type Symbiont within the Lone Star Tick,Amblyomma americanum

Abstract

A Coxiella-type microbe occurs at 100% frequency in all Amblyomma americanum ticks thus far tested. Using laboratory-reared ticks free of other microbes, we identified the Amblyomma-associated Coxiella microbe in several types of tissue and at various stages of the life cycle of A. americanum by 16S rRNA gene sequencing and diagnostic PCR. We visualized Amblyomma-associated Coxiella through the use of a diagnostic fluorescence in situ hybridization (FISH) assay supplemented with PCR-based detection, nucleic acid fluorescent staining, wide-field epifluorescence and confocal microscopy, and transmission electron microscopy (TEM). Specific fluorescent foci were observed in several tick tissues, including the midgut and the Malpighian tubules, but particularly bright signals were observed in the granular acini of salivary gland clusters and in both small and large oocytes. TEM confirmed intracellular bacterial structures in the same tissues. The presence of Amblyomma-associated Coxiella within oocytes is consistent with the vertical transmission of these endosymbionts. Further, the presence of the Amblyomma-associated Coxiella symbiont in other tissues such as salivary glands could potentially lead to interactions with horizontally acquired pathogens.

Coinfection of Dermacentor silvarum Olenev (Acari: Ixodidae) by Coxiella-Like, Arsenophonus-Like, and Rickettsia-Like Symbionts

“…Previous studies have suggested that the Coxiella-like symbiont in A. americanum is a primary symbiont because of its ubiquitous distribution (21,30), vertical transmission (13,21), infection of specific tissues (13), loss of fitness with antibiotic treatment (31), and reduced genome (30). In this study, we found that CLS-Ds exhibited vertical infection and infected specific tissues.…”

“…To date, a wide range of symbionts, such as Coxiella-like (13), Francisella-like (14), Wolbachia-like (15), Rickettsia-like (16), Arsenophonus-like (17), "Candidatus Midichloria mitochondrii" (18), and Rickettsia peacockii (19) symbionts, have been detected in several tick species. However, little attention has been given to coinfection with multiple symbionts of ticks.…”

Comparative Genomics Reveal Extensive Transposon-Mediated Genomic Plasticity and Diversity among Potential Effector Proteins within the GenusCoxiella

“…These pathogens are apparently in the final stages of host cell adaptation and have cleared most pseudogenes from their respective genomes (2). A nonpathogenic progenitor of C. burnetii has not been identified; however, Coxiella-like endosymbionts of ticks are highly prevalent and may represent nonpathogenic ancestors of virulent C. burnetii (57).…”

Coxiella-like Endosymbionts

“…Recently, many Coxiella -like bacteria have been reported in ticks. Ticks infected with Coxiella -like bacteria include Amblyomma americanum Klyachko et al 2007 ;Clay et al 2008 ) , Carios capensis (Reeves et al 2005 ) , Haemaphysalis longicornis (Noda et al 1997 ;Lee et al 2004 ) , Ixodes ricinus (Schabereiter-Gurtner et al 2003 ) , I. woodi (Kurtti et al 2002 ) , Ornithodoros moubata (Noda et al 1997 ) , Rhipicephalus sanguineus (Noda et al 1997 ;Bernasconi et al 2002 ) , and R. turanicus (Bernasconi et al 2002 ) .…”