Phylogenetic analysis of the 16S rDNA of the cytoplasmic bacterium Wolbachia from the novel host Folsomia candida (Hexapoda, Collembola) and its implications for wolbachial taxonomy

Wolbachia pipientis are intracellular, transovarially inherited alpha-Prote obacteria in invertebrates. Four major Wolbachia groups exist: A, B (contai ned in divergent arthropods), C and D (harbored by Nematoda). By means of t ransmission electron microscopy, we observed Wolbachia-like bacteria in a p rimitive insect, Folsomia candida (Hexapoda, Collembola, Isotomidae), 16S r DNA analysis proved them to constitute a novel lineage, henceforth named gr oup E, in the wolbachial phylogenetic tree. It shares 97.8% 16S rDNA homolo gy with its nearest neighbors, groups A and B, which diverged from it more recently. We propose (i) a new taxon E for the Wolbachia strain in F. candi da, (ii) that the single-described Wolbachia pipientis fall apart into at l east three species: C, D and the large E-A-B complex. F. candida's group E Wolbachia rekindle the question about invasive capacities of free-living an cestral wolbachiae and horizontal transfer. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights r eserved.