16S rRNA gene phylogeny based on S-endosymbionts of arthropods and some closely related free-living bacteria. The S-endosymbionts have the prefix SS followed by the proper name of their host, whereas free-living bacteria have proper binomial nomenclature. Only bootstrap values greater than 60% are shown adjacent to each node. The GenBank accession numbers for the 16S rRNA gene sequences are as follows: P. agglomerans, AF373196; E. coli, U00096; S. entomophila, AJ233427; Y. enterocolitica, AF366378; “Candidatus Phlomobacter betae,” AY057392; P. mirabilis, AF008582; P. luminescens, BX571859; SS Glossina morsitans, AY861704; SS(R) Acyrthosiphon pisum, AY620432; SS Pseudolynchia canariensis, DQ115536; SS Glycaspis brimblecombei, AF263561; SS Nasonia vitripennis, M90801; SS Triatoma infestans, U91786; SS Dermacentor variabilis, AY265347; SS Diaphorina citrii, AB038366; SS Tetraleurodes acacia, AY264670; SS Acanthaleyrodes styraci, AY264663; SS Neomaskellia andropogonis, AY264668; SS Australiococcus greville, AY264673; SS Heteropsylla texana, AF263562; SS Wahlgreniella nervata, AY136168; SS Myzocallis spp., AY136153; SS Siphoninus phillyreae, AY264669; SS Aphis spiraecola, AY136142; SS(T) Acyrthosiphon pisum, AY462101; SS(U) Acyrthosiphon pisum, AY462102.