A bacterial strain designated SBKo001(T) was isolated from a forest soil sample from Mt Makiling in Laguna, Philippines. It shows the general characteristics associated with myxobacteria, such as swarming of Gram-negative, rod-shaped vegetative cells, fruiting body formation and bacteriolytic activity. The strain is mesophilic, strictly aerobic and chemoheterotrophic and also exhibits resistance to various antibiotics. Major fatty acids are iso-C(15 : 0), C(17 : 1) 2-OH and C(20 : 4) (arachidonic acid). The G+C content of the genomic DNA is 69.2 mol%. A reference strain, NOSO-1 (=DSM 53757), isolated from the Etosha Basin in Namibia, shares nearly the same characteristics with SBKo001(T). The identical 16S rRNA gene sequences of the two strains show 94 % identity to strains of the cellulose-degrading Byssovorax and Sorangium species. Phylogenetic analysis reveals a novel branch diverging from the Polyangiaceae, Sorangiineae, Myxococcales. Their uniqueness in morphological growth stages, unusual fatty acid profile, broad-spectrum antibiotic resistance and branch divergence from the Polyangiaceae imply that strains SBKo001(T) and NOSO-1 not only represent a novel genus and species, proposed here as Phaselicystis flava gen. nov., sp. nov., but also belong to a new family, Phaselicystidaceae fam. nov. The type strain of Phaselicystis flava is SBKo001(T) (=DSM 21295(T) =NCCB 100230(T)).