Phylogenetic placement of the symbiotic bacteria from the acanthosomatid stinkbugs in the γ- Proteobacteria on the basis of groEL gene sequences. A total of 1040 aligned nucleotide sites at first and second codon positions were subjected to the analysis. The third codon positions were not used because of saturated nucleotide substitutions. Analysis of deduced amino acid sequences gave substantially the same results (data not shown). A Bayesian tree is shown. Support values for the nodes are indicated as in Figure 3. Asterisks indicate support values lower than 50%. Sequence accession numbers are in brackets. Percent AT contents of the sequences are in parentheses. Note that the AT-content values are based on the data of all codon positions.