Spiroplasma Isolated From Third-Generation Laboratory Colony Ixodes persulcatus Ticks.

Alexandra Beliavskaia,Lesley Bell-Sakyi,Jiri Cerny,Martin Palus,Ana M Palomar,Irina Kozlova,Tereza Vyhlidalova,Vaclav Hönig,Daniel Ruzek,Jan Erhart

doi:10.3389/fvets.2021.659786

Abstract

Spiroplasma are vertically-transmitted endosymbionts of ticks and other arthropods. Field-collected Ixodes persulcatus have been reported to harbour Spiroplasma, but nothing is known about their persistence during laboratory colonisation of this tick species. We successfully isolated Spiroplasma from internal organs of 6/10 unfed adult ticks, belonging to the third generation of an I. persulcatus laboratory colony, into tick cell culture. We screened a further 51 adult male and female ticks from the same colony for presence of Spiroplasma by genus-specific PCR amplification of fragments of the 16S rRNA and rpoB genes; 100% of these ticks were infected and the 16S rRNA sequence showed 99.8% similarity to that of a previously-published Spiroplasma isolated from field-collected I. persulcatus. Our study shows that Spiroplasma endosymbionts persist at high prevalence in colonised I. persulcatus through at least three generations, and confirms the usefulness of tick cell lines for isolation and cultivation of this bacterium.

Highlights

Ixodid ticks naturally harbour a variety of bacterial symbionts that may be obligately or facultatively intracellular and are transovarially transmitted
When the tick cell cultures were examined by Giemsa-stained cytocentrifuge smear on day 53 p.i., bacteria resembling Spiroplasma were seen in cells that had received organs from 1/5 male and 5/5 female I. persulcatus ticks (Table 1)
It was not possible to determine whether this was due to differences between the cell lines or the Spiroplasma isolates, in previous studies background material was visible in Spiroplasma-containing vacuoles in cells of the tick cell lines BME/CTVM23 and DALBE3 [21] but not of the tick cell lines IRE11, IRE/CTVM19 or IDE2 [20]

Summary

Introduction

Ixodid ticks naturally harbour a variety of bacterial symbionts that may be obligately or facultatively intracellular and are transovarially transmitted. These include species of the genera Rickettsia, Coxiella, Midichloria and Spiroplasma that occur with high frequency [1,2,3,4] and less common or well-characterised species of the genus Francisella [1, 3] and Occidentia [5]. The unfed or partially-fed ticks had been collected from the field, and bacteria were isolated directly from homogenised/macerated whole ticks or aseptically-dissected internal organs, or from eggs laid by engorged female ticks

Methods

Results

Conclusion