"Candidatus Midichloria" Endosymbionts Bloom after the Blood Meal of the Host, the Hard Tick Ixodes ricinus

Dipartimento di Patologia Animale, Igiene e Sanità Pubblica Veterinaria, Università degli Studi di Milano, Milan, Italy.
Applied and Environmental Microbiology (Impact Factor: 3.67). 09/2008; 74(19):6138-40. DOI: 10.1128/AEM.00248-08
Source: PubMed


"Candidatus Midichloria mitochondrii," an intracellular symbiont of the tick Ixodes ricinus, is the only described organism able to invade the mitochondria of any multicellular organism. We used quantitative PCR to examine cycles of bacterial growth and death throughout the host's development and found that they correspond with the phases of engorgement and molt, respectively.

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Available from: Sara Epis, Jan 08, 2014
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    • "However, the available data regarding the localization of the M. mitochondrii population in the organs of immature stages of I. ricinus suggests the presence only in the primordia of the genital apparatus (Epis et al., 2013). Additionally the amount of M. mitochondrii found in larvae is known to be lower than the load of nymphs or adult females (Sassera et al., 2008). An alternative hypothesis could be that larvae can transmit M. mitochondrii but in quantity that are insufficient to be detected by our method. "
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    ABSTRACT: Midichloria mitochondrii is the most prevalent symbiont of the hard tick Ixodes ricinus, present in 100% of eggs and adult females of wild ticks. This bacterium is intracellular, and is the only known symbiont able to invade the mitochondria of the host cells. However, the role that M. mitochondrii plays in the host metabolism has yet to be elucidated. Multiple lines of evidence indicate the possibility of transmission of this bacterium to the vertebrate host during the tick blood meal. In order to investigate the role of M. mitochondrii in the biology of the tick host, we performed an antibiotic treatment on Ixodes ricinus individuals, with the aim of reducing/eliminating the symbiont, and to potentially observe the dynamic of bacterial infection in the tick host. We microinjected engorged adult females of I. ricinus with tetracycline, and we allowed the resulting larvae to feed on gerbils treated with the same antibiotic. The amount of M. mitochondrii was evaluated at different stages of the experiment using molecular techniques. In addition we evaluated the presence/absence of the symbiont DNA in the blood of gerbils used for the larval feeding. The performed treatments did not allow to eliminate the symbiont population from the host tick, however it allowed to reduce the multiplication that occurs after the larval blood meal. These results open the way for future experiments, using different antibiotic molecules, different administration methods and antibiotic administration on subsequent tick stages, to fulfill the goal of eliminating M. mitochondrii from the host I. ricinus, a major step in our understanding of the impact of this bacterium on ticks. Copyright © 2015 Elsevier GmbH. All rights reserved.
    Ticks and Tick-borne Diseases 05/2015; 6(5). DOI:10.1016/j.ttbdis.2015.05.011 · 2.72 Impact Factor
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    • "Ca. Midichloria mitochondrii, the symbiont of Ixodes ricinus, has the unique ability to enter and destroy mitochondria within ovarian cells of host [21,22], which is coupled with the process of engorgement and molt [23,24]. In addition, colonization of Dermacentor variabilis by R. peacockii can prevent secondary infection with other Rickettsia bacteria, including pathogenic species [25]. "
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    ABSTRACT: Close relationships between ticks and microbial communities are important for tick fitness and pathogen colonization and transmission. Haemaphysalis longicornis, distributed widely in China, can carry and transmit various pathogens and pose serious damages to public health and economics. However, little is known about the broader array of microbial communities and symbionts in H. longicornis under natural conditions. In the present study, we investigated the composition of bacterial communities associated with H. longicornis and evaluated the putative symbionts. The eubacterial 16S rRNA gene clone libraries of H. longicornis were constructed and analyzed by restriction fragment length polymorphism (RFLP) and DNA sequencing. In addition, diagnostic PCR was performed to assess the prevalence, vertical transmission and infection sites of the symbionts in H. longicornis. Vertically-transmitted symbionts, potential pathogens and allochthonous nonpathogenic bacteria were identified from the field-collected H. longicornis. Three types of symbionts (Coxiella-like, Arsenophonus-like and Rickettsia-like symbionts) were identified in a single host simultaneously. A series of analyses revealed the vertical transmission, prevalence, and infection sites of these symbionts. However, only Coxiella-like bacteria were transmitted stably in the laboratory-reared ticks. In addition, we identified a novel Coxiella-like agent with 95.31% sequence similarity to the taxon described previously. The present study demonstrated that natural H. longicornis harboured a diverse array of microbial communities. Three types of symbionts were identified in a single host simultaneously. Moreover, high prevalence, vertical transmission and the infection sites supported an obligate symbiotic association between Coxiella symbiont and its host. The role of Coxiella symbiont in the host fitness and the interaction among microbial communities remained to be elucidated. Our investigation of microbial communities in the ticks revealed the complexity of ecological interactions between host and microbe and provided insight for the biological control of ticks.
    Parasites & Vectors 10/2013; 6(1):310. DOI:10.1186/1756-3305-6-310 · 3.43 Impact Factor
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    • "We emphasize that we cannot be certain that all of the subjects had been parasitized by I. ricinus; in addition, for some of the subjects, the duration of the blood meal could have been insufficient for an effective inoculation of bacteria. Furthermore, some I. ricinus nymphs present a very low M. mitochondrii load,19 thus possibly resulting in inoculation of a low amount of bacteria during their blood meal. These considerations could explain why not all of the parasitized subjects were seropositive for this bacterium. "
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    ABSTRACT: Midichloria mitochondrii is an intracellular bacterium found in the hard tick Ixodes ricinus. In this arthropod, M. mitochondrii is observed in the oocytes and in other cells of the ovary, where the symbiont is present in the cell cytoplasm and inside the mitochondria. No studies have so far investigated whether M. mitochondrii is present in the salivary glands of the tick and whether it is transmitted to vertebrates during the tick blood meal. To address the above issues, we developed a recombinant antigen of M. mitochondrii (to screen human sera) and antibodies against this antigen (for the staining of the symbiont). Using these reagents we show that (i) M. mitochondrii is present in the salivary glands of I. ricinus and that (ii) seropositivity against M. mitochondrii is highly prevalent in humans parasitized by I. ricinus (58%), while it is very low in healthy individuals (1·2%). These results provide evidence that M. mitochondrii is released with the tick saliva and raise the possibility that M. mitochondrii is infectious to vertebrates. Besides this, our study indicates that M. mitochondrii should be regarded as a package of antigens inoculated into the human host during the tick bite. This implies that the immunology of the response toward the saliva of I. ricinus is to be reconsidered on the basis of potential effects of M. mitochondrii and poses the basis for the development of novel markers for investigating the exposure of humans and animals to this tick species.
    11/2012; 106(7):391-6. DOI:10.1179/2047773212Y.0000000050
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