Wide distribution and diversity of members of the bacterial kingdom Acidobacterium in the environment

To assess the distribution and diversity of members of the recently identif ied bacterial kingdom Acidobacterium, members of this kingdom present in 43 environmental samples were surveyed by PCR amplification. A primer designe d to amplify rRNA gene sequences (ribosomal DNAs [rDNAs]) from most known m embers of the kingdom was used to interrogate bulk DNA extracted from the s amples. Positive PCR results were obtained with all temperate soil and sedi ment samples tested, as well as some hot spring samples, indicating that me mbers of this kingdom are very widespread in terrestrial environments. PCR primers specific for four phylogenetic subgroups within the kingdom were us ed in similar surveys. All four subgroups were detected in most neutral soi ls and some sediments, while only two of the groups were seen in most low-p H environments. The combined use of these primers allowed identification of a novel lineage within the kingdom in a hot spring environment. Phylogenet ic analysis of rDNA sequences from our survey and the literature outlines a t least six major subgroups within the kingdom. Taken together, these data suggest that members of the Acidobacterium kingdom are as genetically and m etabolically diverse, environmentally widespread and perhaps as ecologicall y important as the well-known Proteobacteria and gram-positive bacterial ki ngdoms.