Group-specific PCR primers for the phylum Acidobacteria designed based on the comparative analysis of 16S rRNA gene sequences.

We performed a comprehensive phylogenetic analysis of the phylum Acidobacteria and developed novel, group-specific PCR primers for Acidobacteria and its class-level subgroups. Acidobacterial 16S rRNA gene sequences deposited in the RDP database were used to construct a local database then subsequently analyzed. A total of 556 phylotypes were observed and the majority of the phylotypes belonged to five major subgroups (subgroups 1, 2, 3, 4, and 6), which comprised >80% of the acidobacterial sequences in the RDP database. Phylum-specific and subgroup-specific primers were designed from the consensus sequences of the phylotype sequences, and the specificities of the designed primers were evaluated both in silico and empirically for coverage and tolerance. The phylum-specific primer ACIDO, which was designed in this study, showed increased coverage for Acidobacteria, as compared to the previous phylum-specific primer 31F. However, the tolerance of the primer ACIDO for non-target sequences was slightly higher than that of the primer 31F. We also developed subgroup-specific PCR primers for the major subgroups of Acidobacteria, except for subgroup 4. Subgroup-specific primers S1, S2, and S3, which targeted subgroups 1, 2, and 3, respectively, showed high coverage for their target subgroups and low tolerance for non-target sequences. However, the primer S6 targeting subgroup 6 showed a lower specificity in its empirical evaluation than expected from the in silico results. The subgroup-specific primers, as well as the phylum-specific primer designed in this study, will be valuable tools in understanding the phylogenetic diversity and ecological niche of the phylum Acidobacteria and its subgroups.