Abstract
Francisella-like endosymbionts (FLEs) with significant homology to Francisella tularensis (γ-proteobacteria) have been characterized in several tick species, whereas knowledge on their distribution and population dynamics in ticks remains meager. Hence, in the current study, we identified a novel Francisella-like endosymbiont (FLEs-Hd) from the tick Haemaphysalis doenitzi and evaluated the putative functions of this symbiont. Results indicated that FLEs-Hd had 100% infection rate and a perfect vertical transmission in H. doenitzi, and that it is distributed in ovaries, malpighian tubules, salivary glands and midguts of the ticks, suggesting that FLEs-Hd presumably is a crucial symbiont of the host without specific tissue tropism. To further explore the function of the symbiont, the population dynamics of FLEs-Hd at each developmental stage of ticks and in tissues at different reproductive statuses were determined by real-time quantitative polymerase chain reaction (real-time qPCR). Results showed that the high density and regular population dynamics of FLEs-Hd appeared in female ovaries, suggesting that the symbiont may provide necessary nutrients or regulators to ensure normal ovary development of ticks.
Highlights
Francisella is an expanding genus of the gamma subdivision of the Proteobacteria with a facultative intracellular life style[1]
Sphingomonas and Acinetobacter were characterized as the main bacteria in H. doenitzi, and a novel Francisella-like endosymbiont was identified and further analyzed
Sphingomonas bacteria have been reported in I. ricinus, I. ovatus, I. persulcatus and H. flava by assays of bacterial communities[26,27]
Summary
Francisella is an expanding genus of the gamma subdivision of the Proteobacteria with a facultative intracellular life style[1]. The tick Dermacentor andersoni was first implicated as a vector of pathogenic F. tularensis[9], and Francisella-like endosymbionts (FLEs) were described in this tick species[10]. Many FLEs closely related to F. tularensis have been identified in ticks belonging to Ornithodoros[11,12], Dermacentor[10,13], Amblyomma[14], Anocentor[15], Hyalomma[16], Rhipicephalus[16] and Ixodes (Genbank accession No JQ740890), whereas no FLEs have yet been identified from ticks within the genus Haemaphysalis. The functions of the putative symbiont were evaluated preliminarily by assaying the population dynamics of the symbiont using real-time quantitative PCR (real-time qPCR), which will provide basic knowledge for further clarification of the relationship between FLEs and the host ticks
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