Genome Analysis and Genomic Comparison of the Novel SpeciesArthrobacter ipsiReveal Its Potential Protective Role in Its Bark Beetle Host

The pine engraver beetle,Ips acuminatusGyll, is a bark beetle that causes important damages in Scots pine (Pinus sylvestris) forests and plantations. As almost all higher organisms,Ips acuminatusharbours a microbiome, although the role of most members of its microbiome is not well understood. As part of a work in which we analysed the bacterial diversity associated toIps acuminatus, we isolated the strainArthrobactersp. IA7. In order to study its potential role within the bark beetle holobiont, we sequenced and explored its genome and performed a pan-genome analysis of the genusArthrobacter, showing specific genes of strain IA7 that might be related with its particular role in its niche. Based on these investigations, we suggest several potential roles of the bacterium within the beetle. Analysis of genes related to secondary metabolism indicated potential antifungal capability, confirmed by the inhibition of several entomopathogenic fungal strains (Metarhizium anisopliaeCCF0966,Lecanicillium muscariumCCF6041,L. muscariumCCF3297,Isaria fumosoroseaCCF4401,I. farinosaCCF4808,Beauveria bassianaCCF4422 andB. brongniartiiCCF1547). Phylogenetic analyses of the 16S rRNA gene, six concatenated housekeeping genes (tuf-secY-rpoB-recA-fusA-atpD) and genome sequences indicated that strain IA7 is closely related toA. globiformisNBRC 12137(T)but forms a new species within the genusArthrobacter; this was confirmed by digital DNA-DNA hybridization (37.10%) and average nucleotide identity (ANIb) (88.9%). Based on phenotypic and genotypic features, we propose strain IA7(T)as the novel speciesArthrobacter ipsisp. nov. (type strain IA7(T)= CECT 30100(T)= LMG 31782(T)) and suggest its protective role for its host.