A new symbiotic lineage related toNeisseriaandSnodgrassellaarises from the dynamic and diverse microbiomes in sucking lice

AbstractPhylogenetic diversity of symbiotic bacteria in sucking lice suggests that lice have experienced a complex history of symbiont acquisition, loss, and replacement during their evolution. By combining metagenomics and amplicon screening across several populations of two louse genera (PolyplaxandHoplopleura) we describe a novel louse symbiont lineage related toNeisseriaandSnodgrassella, and show its’ independent origin within dynamic lice microbiomes. While the genomes of these symbionts are highly similar in both lice genera, their respective distributions and status within lice microbiomes indicate that they have different functions and history. InHoplopleura acanthopus, theNeisseria-related bacterium is a dominant obligate symbiont universally present across several host’s populations, and seems to be replacing a presumably older and more degenerated obligate symbiont. In contrast, thePolyplaxmicrobiomes are dominated by the obligate symbiontLegionella polyplacis, with theNeisseria-related bacterium co-occurring only in some samples and with much lower abundance.