Diversity of endosymbiont bacteria associated with a non-filarial nematode group

There is a significant knowledge gap with regard to non-filarial nematodes and their relationships, if any, with intracellular bacteria, with only sporadic reports in the literature. An intracellular bacteria Xiphinematobacter, belonging to subdivision 2 of the Verrucomicrobia, was previously reported in the ovaries of three species of the non-filarial Xiphinema americanum-group of nematodes. We explored the diversity of Xiphinematobacter in 22 populations of X. americanum sourced from six continents and conservatively have identified nine phylotypes, six of which have not previously been reported. A geographic basis to the phylotypes was noted with phylotypes A and B only found in Europe, whereas phylotypes F, G, H and I were mainly found in North America. Phylotypes C, D and E showed greater geographical variation. Sequences of Xiphinematobacter from this study help to inform the taxonomy of Verrucomicrobia such that the status and composition of Verrucomicrobia subdivision 2 potentially requires reflection.