Biotic Factors Influence Microbiota of Nymph Ticks from Vegetation in Sydney, Australia

Abstract

Ticks are haematophagous ectoparasites of medical and veterinary significance due to their excellent vector capacity. Modern sequencing techniques enabled the rapid sequencing of bacterial pathogens and symbionts. This study’s aims were two-fold; to determine the nymph diversity in Sydney, and to determine whether external biotic factors affect the microbiota. Tick DNA was isolated, and the molecular identity was determined for nymphs at the cox1 level. The tick DNA was subjected to high throughput DNA sequencing to determine the bacterial profile and the impact of biotic factors on the microbiota. Four nymph tick species were recovered from Sydney, NSW: Haemaphysalis bancrofti, Ixodes holocyclus, Ixodes trichosuri and Ixodes tasmani. Biotic factors, notably tick species and geography, were found to have a significance influence on the microbiota. The microbial analyses revealed that Sydney ticks display a core microbiota. The dominating endosymbionts among all tick species were Candidatus Midichloria sp. Ixholo1 and Candidatus Midichloria sp. Ixholo2. A novel Candidatus Midichloria sp. OTU_2090 was only found in I. holocyclus ticks (nymph: 96.3%, adult: 75.6%). Candidatus Neoehrlichia australis and Candidatus Neoehrlichia arcana was recovered from I. holocyclus and one I. trichosuri nymph ticks. Borrelia spp. was absent from all ticks. This study has shown that nymph and adult ticks carry different bacteria, and a tick bite in Sydney, Australia will result in different bacterial transfer depending on tick life stage, tick species and geography.

Unbiased Characterization of the Microbiome and Virome of Questing Ticks

“…in this study strongly supports their standing in the core microbiota of I. holocyclus . Chandra and Šlapeta (2020) , detected Ca. Neoehrlichia spp.…”

“…In Australia, only a small number of metagenomic studies utilizing 16S rRNA gene targeted amplicon sequencing studies have been undertaken to elucidate the bacterial proponent of the tick microbiome and virome ( Gofton et al, 2015a ; Panetta et al, 2017 ; Chandra and Šlapeta, 2020 ). Similarly, only two studies have applied metagenomic technologies to determine the viral profile, or virome, of Australian ticks ( O’Brien et al, 2018 ; Harvey et al, 2019 ).…”

“…Neoehrlichia australis and Ca. Neoehrlichia arcana in I. holocyclus and one Ixodes trichosuri Roberts, 1960 ( Gofton et al, 2015a ; Gofton et al, 2016 ; Chandra and Šlapeta, 2020 ). The presence of the endosymbiont Ca.…”

“…To date, there has been no evidence supporting locally acquired B. burgdorferi s.l. infections as the spirochaete has not yet been found in Australia ( Russell et al, 1994 ; Gofton et al, 2015a ; Collignon et al, 2016 ; Chalada et al, 2018 ; Chandra and Šlapeta, 2020 ). Several studies have been undertaken in search of a causative agent for tick associated disease in the region, although these have largely utilized a 16S rRNA gene sequencing approach which limits pathogen discovery to bacterial species ( Greay et al, 2018 ; Chandra and Šlapeta, 2020 ).…”

“…infections as the spirochaete has not yet been found in Australia ( Russell et al, 1994 ; Gofton et al, 2015a ; Collignon et al, 2016 ; Chalada et al, 2018 ; Chandra and Šlapeta, 2020 ). Several studies have been undertaken in search of a causative agent for tick associated disease in the region, although these have largely utilized a 16S rRNA gene sequencing approach which limits pathogen discovery to bacterial species ( Greay et al, 2018 ; Chandra and Šlapeta, 2020 ). In recent years, only two studies have explored the virome of Australian ticks, which have identified 20 novel RNA virus species, with one predicted to have pathogenic potential based on its phylogenetic relationship to other arboviruses in the Coltivirus genus ( O’Brien et al, 2018 ; Harvey et al, 2019 ).…”