An Insight Into the Microbiome of theAmblyomma maculatum(Acari: Ixodidae)

Abstract

The aim of this study was to survey the bacterial diversity of Amblyomma maculatum Koch, 1844, and characterize its infection with Rickettsia parkeri. Pyrosequencing of the bacterial 16S rRNA was used to determine the total bacterial population in A. maculatum. Pyrosequencing analysis identified Rickettsia in A. maculatum midguts, salivary glands, and saliva, which indicates successful trafficking in the arthropod vector. The identity of Rickettsia spp. was determined based on sequencing the rickettsial outer membrane protein A (rompA) gene. The sequence homology search revealed the presence of R. parkeri, Rickettsia amblyommii, and Rickettsia endosymbiont of A. maculatum in midgut tissues, whereas the only rickettsia detected in salivary glands was R. parkeri, suggesting it is unique in its ability to migrate from midgut to salivary glands, and colonize this tissue before dissemination to the host. Owing to its importance as an emerging infectious disease, the R. parkeri pathogen burden was quantified by a rompB-based quantitative polymerase chain reaction (qPCR) assay and the diagnostic effectiveness of using R. parkeri polyclonal antibodies in tick tissues was tested. Together, these data indicate that field-collected A. maculatum had a R. parkeri infection rate of 12–32%. This study provides an insight into the A. maculatum microbiome and confirms the presence of R. parkeri, which will serve as the basis for future tick and microbiome interaction studies.

Tick microbiome: the force within

“…Moreover, humans and animals bitten by these ticks were seropositive to the endosymbiont bacterial antigens [38, 39]. Further, Budachtri et al [40] showed that Amblyomma maculatum were predominantly infected with Francisella, Wolbachia and rickettsial species and sequences corresponding to rickettsial outer membrane protein-encoding genes ( ompA and ompB ) were also observed in salivary glands suggesting that these endosymbionts had the potential for transmission to the vertebrate host. While most tick-borne endosymbionts were thought to be innocuous passengers [22, 41], these observations question that presumption.…”

“…Different studies have used different hypervariable regions of the 16S rDNA [56] (V1-V3, V4, V5, or V6, regions) and examined different tick stages from diverse geographic locations in the world (Table 1). Further, while most studies have utilized whole ticks, only a handful has utilized specific tissues dissected from the ticks [40, 57-59]. The limitation of using whole ticks is that it does not allow one to define the tissue-specific microbiome [60] and this understanding might be pertinent to derive functional inferences in the context of the biology of the tick and its interactions with tick-borne pathogens.…”

“…Across all genospecies of hard ticks, bacteria of the phylum Proteobacteria are predominant followed by Actinobacteria, Firmicutes and Bacteroidetes . Bacterial members of the phylum Acidobacteria, Cyanobacteria, Fusobacteria and TM7 are also observed at lower levels in some studies [40, 58]. Both aerobic and anaerobic bacteria were observed, and Gram-negative bacteria were predominant [48].…”

Variation in the Microbiota of Ixodes Ticks with Regard to Geography, Species, and Sex

“…While there have been many studies of tick microbiomes (11)(12)(13)(14)(15)(16)(17), relatively little is known about the microbiota of Ixodes ticks. Efforts to identify microbial commensals and symbionts have been made using culture-based methods (18), cloning, and sequencing of gel-purified PCR products (4).…”

Looking in ticks for human bacterial pathogens

“…This study revealed the presence of bacteria of 121 genera, including Borrelia, Coxiella, Wolbachia and Legionella. Among others, microbiomes of Ixodes ricinus [25], Amblyomma testudinarium, Amblyomma variegatum, Haemaphysalis formosensis, Haemaphysalis longicornis, Ixodes ovatus, Ixodes persulcatus [26], Amblyomma americanum [27], and Amblyomma maculatum [28] were analyzed. 454-and Illumina-based metagenomic approaches were used along with pyrosequencing of bacteriaenriched whole genome or prokaryotic 16S rRNA.…”