Phylogenetic characterisation of two novel Anaplasmataceae from Australian Ixodes holocyclus ticks: ‘Candidatus Neoehrlichia australis' and ‘Candidatus Neoehrlichia arcana'

Abstract

Recently, two novel species of Anaplasmataceae were detected in the Australian paralysis tick, Ixodes holocyclus, by 16S rRNA gene metabarcoding. Analysis of these sequences suggested that these novel organisms are closely related to the genus 'Candidatus Neoehrlichia'. In this study, phylogenetic analysis of 16S rRNA (1264 bp), groESL (1047 bp) and gltA (561 bp) gene sequences, and concatenated (2872 bp) sequences, all concur that these novel species belong in the genus 'Candidatus Neoehrlichia' and are most closely related to, but distinct from the only other recognised members of this genus, 'Candidatus Neoehrlichia mikurensis' and 'Candidatus Neoehrlichia lotoris'. Based on their unique molecular signature, we propose to designate these species 'Candidatus Neoehrlichia australis' (reference strain HT41R) and 'Candidatus Neoehrlichia arcana' (reference strain HT94R). Identical 'Candidatus Neoehrlichia australis' 16S rRNA, groESL and gltA sequences were detected in 34/391 (8.7 %) individual Ixodes holocyclus ticks, and sequences were most similar to 'Candidatus Neoehrlichia lotoris' (96.2 %, 83.1 % and 67.2 %, respectively) and 'Candidatus Neoehrlichia mikurensis' (96.2 %, 84 % and 68.4 % respectively). Likewise, identical 'Candidatus Neoehrlichia arcana' 16S rRNA, groESL and gltA sequences were detected in 12/391 (3.1 %) Ixodes holocyclus ticks, and sequences were most similar to 'Candidatus Neoehrlichia lotoris' (98.5 %, 88.7 % and 79.3 %, respectively) and 'Candidatus Neoehrlichia mikurensis' (96.3 %, 84 % and 67.4 % respectively). These new species are the first Anaplasmataceae (except Wolbachia spp.) to be found to be endemic to Australia. The pathogenic consequences of these organisms are yet to be determined.