Genomic sequences of Lightella neohaematopini, symbiont of Neohaematopinus pacificus sucking lice.

Sucking lice (Anoplura) are known to have established multiple times symbiotic associations with different groups of bacteria, as diverse as Enterobacteriales, Legionellales, or Neisseriales. This diversity, together with absence of a common coevolving symbiont (such as e.g., Buchnera in aphids), indicates that sucking lice underwent series of the symbionts acquisitions, losses, and replacements. To better understand evolution and significance of the louse symbionts, genomic and phylogenetic data are needed from a broader taxonomic sample across the diversity of lice. In this study, we extend the known spectrum of the louse symbionts with a new lineage, associated with chipmunk lice Neohaematopinus pacificus. Recent coevolutionary analysis showed that, rather than single species, these lice form a cluster of separated phylogenetic lineages specific to single chipmunk species (or group of closely related species). Using metagenomic assemblies, we show that the lice harbour a bacterium which mirrors their phylogeny and displays traits typical for obligate mutualists. Phylogenetic analysis places this bacterium within Enterobacteriacea on a long branch related to another louse symbiont, Candidatus Puchtella pedicinophila. We propose for this symbiotic lineage the name Candidatus Lightella neohaematopini. Based on the reconstruction of metabolic pathways, we suggest that like other louse symbionts, L. haematopini provides its host at least with some B vitamins. In addition, several samples harboured another symbiotic bacterium phylogenetically affiliated with the Neisseriales-related symbionts described previously from the lice Polyplax serrata and Hoplopleura acanthopus.