Planifilum composti sp. nov., a thermophile isolated from compost

Two thermophilic bacteria, designated strains P8^T and P12, were isolated from compost in Korea. The isolates grew aerobically from 50 to 75 °C (optimum at 55 °C) and at pH 4.0–9.0 (optimum pH 6.5). Aerial mycelia were not observed. Single spores were produced along the substrate hypha. The predominant menaquinone was MK-7. Major fatty acids were iso-C_17 : 0, iso-C_15 : 0 and iso-C_16 : 0. The cell wall contained meso-diaminopimelic acid and the polar lipids were phosphatidylethanolamine, an aminophospholipid and sphingoglycolipid. The DNA G+C contents were 55.9–56.5 mol%. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strains P8^T and P12 belonged to the genus Planifilum in the family Thermoactinomycetaceae with sequence similarities of 96.1–97.2 %. Levels of DNA–DNA relatedness between strain P8^T and the type strains of recognized species of the genus Planifilum ranged from 28.9 to 38.2 %. On the basis of data from the present polyphasic study, strains P8^T and P12 are considered to represent a novel species of the genus Planifilum, for which the name Planifilum composti sp. nov. is proposed. The type strain is P8^T ( = KACC 16581^T = NBRC 108858^T).