Diversity of the culturable lichen-derived actinobacteria and the taxonomy of Streptomyces parmotrematis sp. nov.

A total of 37 actinobacteria were isolated from eighteen lichen samples collected in Thailand. Based on the 16S rRNA gene sequences, they were identified into five genera including Actinoplanes (1 strain), Actinomadura (1 strain), Pseudosporangium (1 strain), Wangella (1 strain) and Streptomyces (33 strains). Among these isolates, strain Ptm05(T), Ptm01 and Ptm12 showed low 16S rRNA gene similarity and was selected for the further taxonomic study using the polyphasic approach. These strains showed the highest 16S rRNA gene sequence similarity with Streptomyces sparsogenes ATCC 25498(T) (97.44-97.72%). Strain Ptm05(T) was selected for the type strain. The chemical cell composition of the strain was similar to the members of Streptomyces genus. LL-diaminopimelic acids were detected in the peptidoglycan. Menaquinones were MK-9(H-8) and MK-9(H-6). Phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, one unidentified phospholipid, one unidentified glycolipid and one unidentified lipid were detected as the polar lipids. The predominant cellular fatty acids are anteiso-C-15:0, iso-C-15:0, iso-C-16:0, iso-C-17:0 and C-16:0. The dDNA-DNA hybridization values among strain Ptm05(T) and its closely related Streptomyces type strains were 17.2-18.0%. In addition, the ANIb and ANIm between strain Ptm05(T) and related Streptomyces type strains were ranged from 75.69 to 76.13% and 85.21 to 85.35%, respectively. Based on phenotypic and genomic evidence, strain Ptm05(T) (= TBRC 14546(T) = NBRC 115203(T)) represents the novel species of the genus Streptomyces for which the name Streptomyces parmotrematis sp. nov. is proposed. This study showed that the lichens are the promising source of the novel actinobacterial taxa.