Genetic Diversity of Tick-Borne Rickettsial Pathogens; Insights Gained from Distant Strains

Rickettsiales are important zoonotic pathogens, causing severe disease in humans globally. Although mosquitoes are an important vector for diverse pathogens, with the exception of members of the genus Wolbachia little is known about their role in the transmission of Rickettsiales. Herein, Rickettsiales were identified by PCR in five species of mosquitoes (Anopheles sinensis, Armigeres subalbatus, Aedes albopictus, Culex quinquefasciatus and Cu. tritaeniorhynchus) collected from three Chinese provinces during 2014–2015. Subsequent phylogenetic analyses of the rrs, groEL and gltA genes revealed the presence of Anaplasma, Ehrlichia, Candidatus Neoehrlichia, and Rickettsia bacteria in mosquitoes, comprising nine documented and five tentative species bacteria, as well as three symbionts/endosybionts. In addition, bacteria were identified in mosquito eggs, larvae, and pupae sampled from aquatic environments. Hence, these data suggest that Rickettsiales circulate widely in mosquitoes in nature. Also of note was that Ehrlichia and Rickettsia bacteria were detected in each life stage of laboratory cultured mosquitoes, suggesting that Rickettsiales may be maintained in mosquitoes through both transstadial and transovarial transmission. In sum, these data indicate that mosquitoes may have played an important role in the transmission and evolution of Rickettsiales in nature.

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“…sinensis and Ar. subalbatus mosquitoes, and that these strains are closely related to widely distributed ruminant strains3149. Additionally, An.…”

Section: Discussionmentioning

confidence: 90%

Extensive genetic diversity of Rickettsiales bacteria in multiple mosquito species

Guo

Tian

Lin³

et al. 2016

Sci Rep

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“…For example, the three largest contigs from the Idaho genome are 305,977, 85,373 and 71,461 bp, while for Oklahoma-2 they are 306,104, 85,373 and 69,474 bp. There are 3 bp mismatches between the two contig 1 s from each sequence, 1 mismatch between the contig 2 s and 0 mismatches between the contig 3 s. This level of sequence identity is unprecedented for two sequences of A. marginale that are different strains, let alone two sequences that are different species [18, 50]. It appears that the same genome was sequenced twice.…”

Section: Resultsmentioning

confidence: 99%

The Anaplasma ovis genome reveals a high proportion of pseudogenes

et al. 2019

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BackgroundThe genus Anaplasma is made up of organisms characterized by small genomes that are undergoing reductive evolution. Anaplasma ovis, one of the seven recognized species in this genus, is an understudied pathogen of sheep and other ruminants. This tick-borne agent is thought to induce only mild clinical disease; however, small deficits may add to larger economic impacts due to the wide geographic distribution of this pathogen.ResultsIn this report we present the first complete genome sequence for A. ovis and compare the genome features with other closely related species. The 1,214,674 bp A. ovis genome encodes 933 protein coding sequences, the split operon arrangement for ribosomal RNA genes, and more pseudogenes than previously recognized for other Anaplasma species. The metabolic potential is similar to other Anaplasma species. Anaplasma ovis has a small repertoire of surface proteins and transporters. Several novel genes are identified.ConclusionsAnalyses of these important features and significant gene families/genes with potential to be vaccine candidates are presented in a comparative context. The availability of this genome will significantly facilitate research for this pathogen.

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“…Illumina paired-end sequencing technology was used, producing 2- by 125-bp-long reads. Reads were filtered through transposon mapping to ensure the presence of an informative transposon/genome junction as described previously (74). Expansion or decrease of fitness of mutants was calculated in fold change with normalized insertion numbers (75).…”

Section: Methodsmentioning

confidence: 99%

RadD Contributes to R-Loop Avoidance in Sub-MIC Tobramycin

Negro

Krin

Pierlé

et al. 2019

mBio

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We have previously identified Vibrio cholerae mutants in which the stress response to subinhibitory concentrations of aminoglycoside is altered. One gene identified, VC1636, encodes a putative DNA/RNA helicase, recently named RadD in Escherichia coli. Here we combined extensive genetic characterization and high-throughput approaches in order to identify partners and molecular mechanisms involving RadD. We show that double-strand DNA breaks (DSBs) are formed upon subinhibitory tobramycin treatment in the absence of radD and recBCD and that formation of these DSBs can be overcome by RNase H1 overexpression. Loss of RNase H1, or of the transcription-translation coupling factor EF-P, is lethal in the radD deletion mutant. We propose that R-loops are formed upon sublethal aminoglycoside treatment, leading to the formation of DSBs that can be repaired by the RecBCD homologous recombination pathway, and that RadD counteracts such R-loop accumulation. We discuss how R-loops that can occur upon translation-transcription uncoupling could be the link between tobramycin treatment and DNA break formation. IMPORTANCE Bacteria frequently encounter low concentrations of antibiotics. Active antibiotics are commonly detected in soil and water at concentrations much below lethal concentration. Although sub-MICs of antibiotics do not kill bacteria, they can have a major impact on bacterial populations by contributing to the development of antibiotic resistance through mutations in originally sensitive bacteria or acquisition of DNA from resistant bacteria. It was shown that concentrations as low as 100-fold below the MIC can actually lead to the selection of antibiotic-resistant cells. We seek to understand how bacterial cells react to such antibiotic concentrations using E. coli, the Gram-negative bacterial paradigm, and V. cholerae, the causative agent of cholera. Our findings shed light on the processes triggered at the DNA level by antibiotics targeting translation, how damage occurs, and what the bacterial strategies are to respond to such DNA damage.

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Genetic Diversity of Tick-Borne Rickettsial Pathogens; Insights Gained from Distant Strains

Cited by 16 publications

References 48 publications

Extensive genetic diversity of Rickettsiales bacteria in multiple mosquito species

Extensive genetic diversity of Rickettsiales bacteria in multiple mosquito species

The Anaplasma ovis genome reveals a high proportion of pseudogenes

RadD Contributes to R-Loop Avoidance in Sub-MIC Tobramycin

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