Paracidobacterium acidisoli gen. nov., sp. nov. and Alloacidobacterium dinghuense gen. nov., sp. nov., two acidobacteria isolated from forest soil, and reclassification of Acidobacterium ailaaui and Acidipila dinghuensis as Pseudacidobacterium ailaaui gen. nov., comb. nov. and Silvibacterium dinghuense comb. nov.

Two aerobic and obligately acidophilic bacteria, designated 4G-K13(T) and 4Y35(T), were isolated from the forest soil sampled at Dinghushan Biosphere Reserve, Guangdong Province, PR China. These two strains were Gram-stain-negative, non-motile and short rods that multiplied by binary division. Strains 4G-K13(T) and 4Y35(T) had the highest 16S rRNA gene sequence similarity of 97.0 and 97.2% to Silvibacterium bohemicum DSM 103733(T) and Acidisarcina polymorpha SBC82(T), respectively. Phylogenetic trees based on the 16S rRNA gene and whole genome sequences showed consistently that these two strains formed a major clade with members of the genera Acidipila, Acidisarcina, Silvibacterium and Acidobacterium in the family Acidobacteriaceae, but each occupied an unique position. In both the UBCG and the PhyloPhlAn phylogenomic trees, strains 4G-K13(T) and 4Y35(T) congruently formed a highly supported subclade with Acidobacterium capsulatum DSM 11244(T) and Acidobacterium ailaaui DSM 27394(T), respectively. The major fatty acids (>5 %) of strain 4G-K13(T) were iso-C 15:0, iso-C-17:0, summed feature 3 (C-16:1 omega 7c and/or C-16:1 omega 6c) and summed feature 9 (iso-C-17:1 omega 9c and/or C-16:0 10-methyl), while that of strain 4Y35(T) were C16:0, C-18:1 omega 9c, iso-C-15:0, summed feature 3 (C-16:1 omega 7c and/or C-16:1 omega 6c) and summed feature 9 (iso-1(7:1) omega 9c and/or C-16:0 10-methyl). Strain 4G-K13(T) contained phosphatidylethanolamine, four unidentified phospholipids, four glycolipids, two unidentified aminolipids and two unknown lipids, while strain 4Y35(T) had phosphatidylethanolamine, three unidentified phospholipids, two glycolipids, five unidentified aminolipids and one unknown polar lipid. The DNA G+C contents of 4G-K13(T) and 4Y35(T) were 60.5 and 55.8 mol%, respectively. Based on all these phylogenetic, physiological and chemotaxonomic data, we suggest that strains 4G-K13(T) and 4Y35(T) represent two novel species of two novel genera in the family Acidobacteriaceae, for which the names Paracidobacterium acidisoli gen. nov., sp. nov. (type strain: 4G-K13(T)=GDMCC 1.1195(T)=NBRC 113249(T)) and Alloacidobacterium dinghuense gen. nov., sp. nov. (type strain: 4Y35(T)=KACC 21728(T)=NBRC 114261(T)) are proposed. We also propose to reclassify Acidobacterium ailaaui and Acidipila dinghuensis as Pseudacidobacterium ailaaui gen. nov., comb. nov. and Silvibacterium dinghuense comb. nov., respectively, based mainly on the results of phylogenomic analysis.