Characterization of the bacterial microbiome of Swedish ticks through 16S rRNA amplicon sequencing of whole ticks and of individual tick organs

Abstract

Background The composition of the microbial flora associated with ixodid ticks has been studied in several species, revealing the importance of geographical origin, developmental stage(s) and feeding status of the tick, as well as substantial differences between tissues and organs. Studying the microbiome in the correct context and scale is therefore necessary for understanding the interactions between tick-borne pathogens and other microorganisms as well as other aspects of tick biology. Methods In the present study the microbial flora of whole Ixodes ricinus, I. persulcatus and I. trianguliceps ticks were analyzed with 16S rRNA amplicon sequencing. Additionally, tick organs (midguts, Malpighian tubules, ovaries, salivary glands) from flat and engorged I. ricinus female ticks were examined with the same methodology. Results The most abundant bacteria belonged to the group of Proteobacteria (Cand. Midichloria mitochondrii and Cand. Lariskella). 16S amplicon sequencing of dissected tick organs provided more information on the diversity of I. ricinus-associated microbial flora, especially when organs were collected from engorged ticks. Bacterial genera significantly associated with tick feeding status as well as genera associated with the presence of tick-borne pathogens were identified. Conclusions These results contribute to the knowledge of microbial flora associated with ixodid ticks in their northernmost distribution limit in Europe and opens new perspectives for other investigations on the function of these bacteria, including those using other approaches like in vitro cultivation and in vitro models. Graphical Abstract

Bacterial community of ticks (Acari: Ixodidae) and mammals from Arauca, Colombian Orinoquia

“…Some Amblyomma ticks (n = 3) were stored in a 2 mL Eppendorf tube in DNA/RNA Shield™ Reagent (Zymo Research) as they originated from the same host. Other ticks were dissected ( Amblyomma : n = 9; Rhipicephalus : n = 5) in sterile phosphate-buffered saline (PBS) at 1% with the assistance of a Zeiss DV4 stereomicroscope to separate the midguts (m), ovaries (o) with oviduct (od), and salivary glands (sg) ( Camargo-Mathias, 2013 , 2018 ; Grandi et al, 2023 ). Subsequently, the organs were separately washed in a 1% PBS solution and pooled by host and each of the organs to be stored in 0.2 mL Eppendorf tubes with DNA/RNA Shield™ Reagent ( Grandi et al, 2023 ).…”

“…The family Ixodidae includes ticks recognized as vectors of bacteria, helminths, protozoa, and viruses that can cause different conditions in humans (e.g., human anaplasmosis, Lyme borreliosis, and tick-borne encephalitis), in domestic animals (e.g., babesiosis and ehrlichiosis), and in wildlife (e.g., rickettsiosis) ( Baneth, 2014 ; Efstratiou et al, 2021 ; Michalski et al, 2021 ; Bezerra-Santos et al, 2022 ; Velásquez-Guarín et al, 2024 ). In addition to pathogens, the set of microbial biotas associated with the tick is defined as the "microbiome" and includes other commensal and endosymbiotic microorganisms that ticks harbor and can be vertically inherited ( Greay et al, 2018 ; Wu-Chuang et al, 2021 ; Grandi et al, 2023 ). Little is known about the role that microorganisms (including bacteria), plays in ticks, they might contribute to the arthropods' fitness by providing nutrients ticks cannot synthesize, such as B group vitamins, among others ( Duron et al, 2015 , 2018 ; Brenner et al, 2021 ; Zhong et al, 2021 ).…”

“…The tick microbiota also seems to play a role in the establishment, maintenance of TBPs infection and transmission, most likely through interaction with the tick's immune system ( Mateos-Hernández et al, 2021 ; Narasimhan et al, 2021 ; Grandi et al, 2023 ). Considering this, the control of tick populations or the associated TBPs could be achieved by manipulating the tick microbiota or particular endosymbionts ( Mateos-Hernández et al, 2021 ; Narasimhan et al, 2021 ).…”

“…However, the evaluations of the dynamics and complexity of the microbiomes associated with the tick diet are still insufficient, and technical limitations might underestimate bacteria with low abundances ( Swei and Kwan, 2017 ; Ross et al, 2018 ; Guizzo et al, 2020 ; Narasimhan et al, 2021 ). Traditionally, research have focused on the occurrence of a single TBP and, in some cases, co-infections ( Couper and Swei, 2018 ; Mateos-Hernández et al, 2021 ; Grandi et al, 2023 ; Sarani et al, 2024 ). Similarly, and despite being part of the tick, host, and pathogen triangle, few studies have highlighted the bacterial communities present in ticks and their wild hosts ( Egan et al, 2021 ; Sarani et al, 2024 ).…”

Molecular characterization of Amblyomma geoemydae using CO1 mitochondrial gene to validate phenotypic taxonomical evaluation

“…While some ticks attach immediately, others scurry around in search of spots with thinner skin, like the ear or other spots (Brandenburg et al 2023 ). During the blood meal uptake, the microbial content is transferred from one body to another, and there are two types of microbial transmission in ticks (Grandi et al 2023 ) before being transmitted to vertebrates, diseases acquired by larval ticks must first be transstadially transmitted to the nymph stage (Ravindran et al 2023 ). The vertical transmission of parasites from an infected vector to its descendants is known as transgenerational transmission (Ebert et al 2023 ; Parola and Raoult 2001 ; Ravindran et al 2023 ; Reis et al 2011 ).…”