Neighbor-joining analysis (1,000 bootstrap replicates, Jukes-Cantor correction) of 1,100 bp of an aligned 16S rDNA sequence for selected CO-oxidizing isolates (indicated by asterisks) and related taxa. Accession numbers for taxa not listed in Table 1: Aminobacter niigataensis, AJ011761; B. japonicum USDA 110, AF363150; B. caledonica, AF215704; B. fungorum LB400, U86373; Hydrogenophaga pseudoflava, AF078770; M. loti, AY278875; M. smegmatis, AJ131761; M. tuberculosis, AJ536031; Oligotropha carboxidotropha, AB099660; R. eutropha CH34, Y10824; R. eutropha, M32021; S. pomeroyi, AF098491; S. aggregata, D88520; Xanthobacter autotrophicus, X94201; and Xanthobacter sp. strain INA43/2-2, AJ306541. Bootstrap values < 50% are not shown. An P. aerophilum sequence was used as an outgroup.