Actinomadura violacea sp. nov., a madurastatin A1-producing strain isolated from lichen in Thailand.

An actinomycete strain, LCR2-06T, isolated from a lichen sample on rock collected from Chiang Rai Province (Pong Phra Bat Waterfall), Thailand, was characterized using a polyphasic approach. The strain grew at 25-45 °C, pH 6-11 and on International Streptomyces Project 2 agar plate with 5 % (w/v) NaCl. It contained meso-diaminopimelic acid as the diamino acid in whole-cell hydrolysates. Rhamnose, ribose, xylose, madurose, glucose and galactose were detected as whole-cell sugar hydrolysates. Mycolic acids were absent. The N-acyl type of muramic acid was acetyl. The strain contained C16 : 0, TBSA 10-methyl C18 : 0 and 2-hydroxy C16 : 0 as the predominant fatty acids and MK-9(H6), MK-9(H4) and MK-9(H8) as the major menaquinones. The major polar lipids were diphosphatidylglycerol, phosphatidylinositol and unidentified phospholipid. The draft genome of strain LCR2-06T was closely related to Actinomadura barringtoniae TBRC 7225T (99.2 %), Actinomadura nitritigenes NBRC 15918T (98.8 %), Actinomadura montaniterrae TISTR 2400T (98.5 %) and Actinomadura physcomitrii JCM 33455T (97.9 %). The draft genome of LCR2-06T was 11.1 Mb with 10 588 coding sequences with an average G+C content of 72.7 mol%. Results of genomic analysis revealed that the ANIb and ANIm values between strain LCR2-06T and A. montaniterrae TISTR 2400T were 90.0 and 92.0 %, respectively. The digital DNA-DNA hybridization value was 43.9 % in comparison with the draft genome of A. montaniterrae TISTR 2400T. The strain produced an antibacterial compound active against Bacillus subtilis ATCC 6633 and Kocuria rhizophila ATCC 9341. The results of taxonomic analysis suggested that strain LCR2-06T represented a novel species of the genus Actinomadura for which the name Actinomadura violacea sp. nov. is proposed. The type strain is LCR2-06T (=JCM 33065T=KCTC 49547T=NBRC 114810T=LMG 32136T=TISTR 2935T).

Actinomadura graeca sp. nov.: A novel producer of the macrocyclic antibiotic zelkovamycin.

As part of a screening programme for antibiotic-producing bacteria, a novel Actinomadura species was discovered from a soil sample collected in Santorini, Greece. Preliminary 16S rRNA gene sequence comparisons highlighted Actinomadura macra as the most similar characterised species. However, whole-genome sequencing revealed an average nucleotide identity (ANI) value of 89% with A. macra, the highest among related species. Further phenotypic and chemotaxonomic analyses confirmed that the isolate represents a previously uncharacterised species in the genus Actinomadura, for which the name Actinomadura graeca sp. nov. is proposed (type strain 32-07T). The G+C content of A. graeca 32-07 is 72.36%. The cell wall contains DL-diaminopimelic acid, intracellular sugars are glucose, ribose and galactose, the predominant menaquinone is MK-9(H6), the major cellular lipid is phosphatidylinositol and fatty acids consist mainly of hexadecanoic acid. No mycolic acid was detected. Furthermore, A. graeca 32-07 has been confirmed as a novel producer of the non-ribosomal peptide antibiotic zelkovamycin and we report herein a provisional description of the unique biosynthetic gene cluster.

Actinomadura soli sp. nov., isolated from the top soil layer on basaltic material in Turkey.

An actinobacterium, designated 14C53T, was isolated from a soil sample on basaltic material from Samsun, Turkey. The growth ranges for NaCl concentration and pH of strain 14C53T were quite limited and the growth temperature range of the strain was 20-37 °C, with an optimum at 28 °C. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain 14C53T was most closely related to Actinomadura geliboluensis A8036T (98.5 % similarity value), but in the phylogenetic tree, it formed a clade with Actinomadura alkaliterrae D310AT. The genome tree revealed a close relationship between the strain and Actinomadura pelletieri DSM 43383T. However, the digital DNA-DNA hybridization and average nucleotide identity values between strain 14C53T with Actinomadura geliboluensis A8036T and Actinomadura pelletieri DSM 43383T were 28.6-30.2 % and 84.3-85.5 %, respectively, and comparative analyses based on the genome sequences demonstrated that it represents a novel species of the genus Actinomadura. The genome size of strain 14C53T was approximately 9.0 Mb and the genomic DNA G+C content of the strain was 71.3 mol%. The major cellular fatty acids of strain 14C53T were C16 : 0 and iso-C16 : 0. Strain 14C53T contained meso-diaminopimelic acid as the diamino acid in the cell-wall peptidoglycan. The predominant menaquinones were MK-9(H8) and MK-9(H6). Based on evidence collected from the phenotypic, genotypic and phylogenetic analyses, a novel species Actinomadura soli sp. nov. is proposed, with 14C53T (=DSM 104447T=KCTC 39878T) as the type strain.