PHYLOGENETIC-RELATIONSHIPS AND UNCERTAIN TAXONOMY OF PEDOMICROBIUM SPECIES

The phylogenetic relationships among the species of the genus Pedomicr obium were studied by comparing their 16S rRNA sequences, The Pedomicr obium species form a coherent phylogenetic cluster within the genera o f the hyphal budding bacteria in the alpha-Proteobacteria. The sequenc es of two strains of Pedomicrobium australicum were obtained from DNAs extracted from nonviable freeze-dried cells, which are the only sourc e of material available, and were found to be almost identical (level of similarity, 99.9%), Overall, the Pedomicrobium species are closely related, with sequence similarities ranging from 96.2 to 99.9%, Pedomi crobium manganicum is phylogenetically the most distantly related spec ies and exhibits the lowest similarity (96.2%) with Pedomicrobium amer icanum, Australian isolate Pedomicrobium sp, strain ACM 3067, P, ameri canum, and P, australicum are all very highly related, with similariti es greater than 99%, Pedomicrobium sp, strain ACM 3067 is most closely related to P, australicum (level of similarity, 99.6%) and P, america num (99.4%), These manganese-oxidizing species are more closely relate d to the iron-oxidizing species Pedomicrobium ferrugineum than to the other manganese-oxidizing species, P, manganicum. Taxonomic uncertaint ies resulting from the loss of the type culture of P, australicum are discussed.