Amycolatopsis mongoliensis sp. nov., a novel actinobacterium with antifungal activity isolated from a coal mining site in Mongolia.

A novel filamentous actinobacterium designated strain 4-36T showing broad-spectrum antifungal activity was isolated from a coal mining site in Mongolia, and its taxonomic position was determined using polyphasic approach. Optimum growth occurred at 30 °C, pH 7.5 and in the absence of NaCl. Aerial and substrate mycelia were abundantly formed on agar media. The colour of aerial mycelium was white and diffusible pigments were not formed. Phylogenetic analyses based on 16S rRNA gene sequence showed that strain 4-36T formed a distinct clade within the genus Amycolatopsis. The 16S rRNA gene sequence similarity showed that the strain was mostly related to Amycolatopsis lexingtonensis DSM 44544T and Amycolatopsis rifamycinica DSM 46095T with 99.3 % sequence similarity. However, the highest digital DNA-DNA hybridization value to closest species was 44.1 %, and the highest average nucleotide identity value was 90.2 %, both of which were well below the species delineation thresholds. Chemotaxonomic properties were typical of the genus Amycolatopsis, as the major fatty acids were C15 : 0, iso-C16 : 0 and C16 : 0, the cell-wall diamino acid was meso-diaminopimelic acid, the quinone was MK-9(H4), and the main polar lipids were diphosphatidylglycerol, phosphatidylmethanolamine and phosphatidylethanolamine. The in silico prediction of chemotaxonomic markers was also carried out by phylogenetic analysis. The genome mining for biosynthetic gene clusters of secondary metabolites in strain 4-36T revealed the presence of 34 gene clusters involved in the production of polyketide synthase, nonribosomal peptide synthetase, ribosomally synthesized and post-translationally modified peptide, lanthipeptide, terpenes, siderophore and many other unknown clusters. Strain 4-36T showed broad antifungal activity against several filamentous fungi. The phenotypic, biochemical and chemotaxonomic properties indicated that the strain could be clearly distinguished from other species of Amycolatopsis, and thus the name Amycolatopsis mongoliensis sp. nov. is proposed accordingly (type strain, 4-36T=KCTC 39526T=JCM 30565T).

Amycolatopsis acidiphila sp. nov., a moderately acidophilic species isolated from coal mine soil.

Little is known on members of the genus Amycolatopsis inhabiting acidic habitats. In this study, a moderately acidophilic Amycolatopsis strain, designated 2-5T, was isolated from coal mine soil, and subjected to a polyphasic taxonomic characterization. Analysis based on 16S rRNA gene sequences indicated that the strain was most closely related to the type strain of Amycolatopsis bartoniae, sharing 99.30 % similarity, while similarity to all other Amycolatopsis species was less than 97 %. The DNA-DNA relatedness between the new isolate and the type strain of A. bartoniae was 56.5±0.7 %. The optimal pH range of the isolate for growth was 5.5-6.0, but growth also occurred at pH 4.5 and 7.5. The isolate tolerated up to 6 % (w/v) NaCl (optimum, 0 %), and the temperature range for growth was 15-40 °C (optimum, 30 °C). The isolate was able to utilize most substrates tested for sole carbon sources, showing its metabolic versatility. The isolate exhibited antimicrobial activity against Serratia marcescens and weak antifungal activity against Fusarium proliferatum. The chemotaxonomic profiles of strain 2-5T included polar lipids containing phosphatidylethanolamine, phsphatidylmethylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol dimannosides, fatty acids containing C17 : 1ω6c and iso-C16 : 0 as the major components, MK-9(H4) as the predominant menaquinone, and meso-diaminopimelic acid and arabinose, galactose, glucose and ribose as the diagnostic diamino acid and sugars in the cell wall. The combined phenotypic, chemotaxonomic and genotypic analyses clearly indicated that the isolate merits recognition as represnting a novel species of Amycolatopsis, for which the name Amycolatopsis acidiphila sp. nov. is proposed. The type strain is 2-5T (=KCTC 39523T=JCM 30562T).