Actinomycetospora termitidis sp. nov., an insect-derived actinomycete isolated from termite (Odontotermes formosanus)

Strain Odt1-22T, an insect-derived actinomycete was isolated from a termite (Odontotermes formosanus) that was collected from Chanthaburi province, Thailand. Strain Odt1-22T was aerobic, Gram-stain-positive, and produced bud-like spore chain on the substrate hypha. According to chemotaxonomic analysis, strain Odt1-22T contained meso-diaminopimelic acid in peptidoglycan and the whole-cell hydrolysates contained arabinose, galactose, glucose, and ribose. The major menaquinone was MK-8(H4). The diagnostic phospholipids were diphosphatidylglycerol, hydroxyphosphatidylethanolamine, phosphatidylethanolamine and phosphatidylglycerol. Phylogenetic analysis based on 16 S rRNA gene sequence revealed that strain Odt1-22T was identified to the genus Actinomycetospora and showed high similarity values with A. chiangmaiensis DSM 45062 T (99.24%), A. soli SF1T (99.24%) and A. corticicola 014-5 T (98.17%). The genomic size of strain Odt1-22T was 6.6 Mbp with 73.8% G + C content and 6355 coding sequences (CDSs). The genomic analysis, strain Odt1-22T and closely related species A. chiangmaiensis DSM 45062 T, A. soli SF1T and A. corticicola DSM 45772 T displayed the values of average nucleotide identity-blast (ANIb) at 83.7-84.1% and MUMmer (ANIm) at 86.6-87.0%. Moreover, the results of digital DNA-DNA hybridization values between strain Odt1-22T and related Actinomycetospora species were 45.8-50.5% that lower than the threshold value of commonly used to delineate separated species level. On the basis of phenotypic, chemotaxonomic, and genotypic data, strain Odt1-22T represented a novel species within the genus Actinomycetospora, for which the name Actinomycetospora termitidis sp. nov. is proposed. The type strain of the species is Odt1-22T (= TBRC 16192 T = NBRC 115965 T).

Frenolicins H and I from the caterpillar-associated Streptomyces sp. TBRC17107

Two undescribed frenolicins H and I (1 and 2) along with six previously described frenolicin analogues [frenolicins A (3), B (4), UCF76-B (5), E - G (6 - 8)] and two anthraquinones [3,8-dihydroxy-1-propylanthraquinone-2-carboxylic acid (9) and 3,8-dihydroxy-1-propylanthraquinone (10)] were isolated from a longkong bark eating caterpillar-derived Streptomyces sp. TBRC17107. The chemical structures were determined by NMR spectroscopic information and HRESIMS data. Frenolicins H (1) and I (2) showed weak cytotoxicity against malignant and non-malignant cells. Frenolicins A (3) and B (4) showed antimalarial activity against Plasmodium falciparum (IC50 17.4 and 1.37 μM), antibacterial activity against Bacillus cereus and Staphylococcus aureus (MIC 50.0 and 0.20 μg/mL). Only frenolicin B had anti-plant pathogenic fungal activity against Collectotrichum acutatum and Alternaria brassicicola with MIC values of MIC 1.56 and 6.25 μg/mL, respectively. Frenolicins A and G possessed anti-Mycobacterium tuberculosis with equal MICs of 25.0 μg/mL.

Streptomyces rugosispiralis sp. nov., a Novel Actinobacterium Isolated from Peat Swamp Forest Soil That Produces Ansamycin Derivatives and Nocardamines

Actinomycetes, especially the genus Streptomyces, are one of the most promising sources of bioactive natural products. In this study, a novel Streptomyces strain, RCU-064T, was isolated from a soil sample collected from a peat swamp forest in Thailand. Strain RCU-064T showed the highest 16S rRNA gene sequence similarity (99.06%) with Streptomyces malaysiensis NBRC 16446T. Based on a polyphasic approach, strain RCU-064T represents a novel species of the genus Streptomyces, for which the name Streptomyces rugosispiralis sp. nov. is proposed. The chemical isolation of the crude ethyl acetate extracts of the strain led to the isolation of six compounds: (1) geldanamycin, (2) 17-O-demethylgeldanamycin, (3) reblastatin, (4) 17-demethoxyreblastatin, (5) nocardamine, and (6) dehydroxynocardamine. These compounds were evaluated for their biological activities. All compounds showed no antimicrobial activity against tested microorganisms used in this study. Compounds (1)-(4) displayed cytotoxic activity against the NCI-H187 cell line, with IC50 values ranging from 0.045-4.250 µg/mL. Cytotoxicity against the MCF-7 cell line was found in compounds (1) and (3) with IC50 values of 3.51 and 1.27 µg/mL, respectively. Compounds (5) and (6) exhibited cytotoxicity only against Vero cells (IC50 of 16.57 µg/mL) and NCI-H187 cells (IC50 of 13.96 µg/mL), respectively. These results indicate that peat swamp forest soil remains a promising reservoir of novel actinomycetes capable of producing bioactive natural products.

Streptomyces macrolidinus sp. nov., a novel soil actinobacterium with potential anticancer and antimalarial activity

A novel actinomycete, strain RY43-2^T, belonging to the genus Streptomyces, was isolated from a peat swamp forest soil collected from Rayong Province, Thailand. The strain was characterized by using a polyphasic approach. The cell-wall peptidoglycan contained ll-diaminopimelic. Ribose and glucose were detected in its whole-cell hydrolysates. The strain contained anteiso-C_15:0, iso-C_14:0 and iso-C_16:0 as the predominant fatty acids, and MK-9(H₄), MK-9(H₆) and MK-9(H₈) as the major menaquinones. The phospholipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, three unidentified ninhydrin-positive phospholipids and two unidentified phospholipids. Strain RY43-2^T showed the highest 16S rRNA gene similarity to Streptomyces misionensis JCM 4497^T (98.9 %) and Streptomyces lichenis LCR6-01^T (98.9 %). The draft genome of RY43-2^T was 6.7 Mb with 6078 coding sequences with an average G+C content of 70.8 mol%. Genomic analysis revealed that the average nucleotide identity (ANI) values based on blast (ANIb) and MUMmer (ANIm) between strain RY43-2^T and S. misionensis JCM 4497^T were 80.1 and 86.1%, respectively. The ANIb and ANIm values between strain RY43-2^T and S. lichenis LCR6-01^T were 77.0 and 85.5%, respectively. The digital DNA-DNA hybridization values were 25.2 and 23.0% in comparison with the draft genomes of S. misionensis JCM 4497^T and S. lichenis LCR6-01^T, respectively. The results of taxonomic analysis suggested that strain RY43-2^T represented a novel species of the genus Streptomyces for which the name Streptomyces macrolidinus sp. nov. is proposed. The type strain is RY43-2^T (=TBRC 7286^T=NBRC 115640^T). Strain RY43-2^T exhibited antimicrobial activity against Enterococcus faecium ATCC 51559, Colletotrichum capsici BMGC 106 and Colletotrichum gloeosporioides BMGC 107 with the minimum inhibitory concentration values of 25.0, 12.5, and 6.25 µg ml^-1. It also exhibited potent antimalarial activity against Plasmodium falciparum K1 with IC₅₀ of 0.0031 µg ml^-1. In addition, it showed cytotoxicity against Vero, KB, MCF-7 and NCI-H187 with IC₅₀ values of 0.0347, 6.15, 3.36 and 0.0352 µg ml^-1, respectively.

Potential antibiotic production of Streptomyces justiciae sp. nov., isolated from the root of Justicia subcoriacea

Endophytic actinobacterial strain 3R004^T was isolated from a root of Justicia subcoriacea collected in Thailand. In this report, the taxonomic position of this strain is described using a polyphasic approach. Based on the morphological characteristics and chemical composition of its cells, strain 3R004^T was identified as a member of the genus Streptomyces. It produced a long chain of cylindrical spores on aerial mycelia. ll-Diaminopimelic acid was detected in the cell wall peptidoglycan. The menaquinones were MK-9(H₄), MK-9(H₆) and MK-9(H₈). C_16 : 0, iso-C_16 : 0, anteiso-C_15 : 0 and iso-C_15 : 0 were detected as the major cellular fatty acids. Polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and one unidentified lipid. Strain 3R004^T showed the highest 16S rRNA gene similarity of 99.45 % to Streptomyces cyaneochromogenes MK-45^T. The phylogenomic results indicated that strain 3R004^T was close to Streptomyces aquilus GGCR-6^T and Streptomyces antibioticus DSM 40234^T. The DNA-DNA hybridization and average nucleotide identity values among strain 3R004^T and closely related Streptomyces species were 35.5-63.1 % and 82.7-94.3 %, respectively. The type strain produced actinomycin D antibiotic as the major secondary metabolite. The maximum productivity of the actinomycin D (378 mg l^-1) was observed when the strain was grown in 301 broth at 30 °C, 180 r.p.m. for 12 days. On the basis of phenotypic and genotypic evidence, strain 3R004^T represents a novel species of the genus Streptomyces, for which the name Streptomyces justiciae is proposed. The type strain is 3R004^T (=LMG 32138^T=TBRC 13128^T=NBRC 115065^T).

Antimicrobial substances from the rare actinomycete Nonomuraea rhodomycinica NR4-ASC07T

Nonomuraea rhodomycinica NR4-ASC07^T is a rare actinomycete isolated from soil in Sirindhorn peat swamp forest. The crude extract of its culture broth exhibited antimicrobial and anticancer against diverse human pathogens and cancer cells. The chemical investigation of the crude extract led to the isolation of two new metabolites named nonomuric acid (1) and 3-hydroxy deoxydaunorubicinol aglycone (2), along with two known bioactive compounds [ε-rhodomycinone (3) and 7-deoxy-13-dihydrocarminomycinone (4)]. Compounds 1 and 3 showed antimalarial activity with the half maximal inhibitory concentration (IC₅₀) of 8.00 and 8.88 μg mL^-1, respectively. Compound 4 inhibited growth of Mycobacterium tuberculosis and Bacillus cereus at the minimum inhibitory concentrations of 50.0 and 12.50 μg mL^-1, respectively. Every compound exhibited cytotoxicity against cancer cells tested at IC₅₀ ≥ 6.34 μg mL^-1. These finding are the first report of bioactive metabolites produced by strain NR4-ASC07^T, suggesting that rare actinomycetes are yet promising sources for novel drug discovery.

Verrucosispora andamanensis sp. nov., isolated from a marine sponge

An actinomycete strain, SP03-05T, was isolated from a marine sponge sample (Xestospongia sp.) collected from Phuket Province of Thailand. The strain was aerobic, Gram-stain-positive and produced single spores at the tips of the substrate mycelium. Strain SP03-05T contained meso-diaminopimelic acid in the peptidoglycan; whole-cell sugars were arabinose, galactose, glucose, rhamnose, ribose and xylose. The polar lipid profile of strain SP03-05T consisted of phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides and unknown polar lipids. Morphological and chemotaxonomic characteristics of the strain identified it as a member of the family Micromonosporaceae . Phylogenetic analysis based on 16S rRNA gene sequences showed similarity of the strain to Verrucosispora lutea YIM 013T (96.90 %), Verrucosispora sediminis MS426T (96.90 %), Verrucosispora gifhornensis DSM 44337T (96.80 %), Verrucosispora maris AB-18-032T (96.80 %) and Verrucosispora qiuiae RtIII47T (95.40 %). The DNA G+C content was 72.4 mol%. The phenotypic, genotypic and DNA–DNA hybridization results supported the classification of this strain as a representative of a novel species in the genus Verrucosispora , for which the name Verrucosispora andamanensis sp. nov. is proposed. The type strain is SP03-05T ( = BCC 45620T = NBRC 109075T).

Micromonospora sediminicola sp. nov., isolated from marine sediment

An actinomycete strain, designated strain SH2-13(T), was isolated from a marine sediment sample collected from the Andaman Sea of Thailand. Applying a polyphasic approach, the isolate was identified as a member of the genus Micromonospora using morphological and chemotaxonomic characteristics, including the presence of meso-diaminopimelic acid in the peptidoglycan. Whole-cell sugars were arabinose, galactose, glucose, rhamnose, ribose and xylose. Diagnostic polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides and phosphoglycolipids. The major menaquinones were MK-10(H(2)), MK-10(H(4)) and MK-10(H(6)). 16S rRNA gene sequence analysis revealed similarity to Micromonospora marina JSM1-1(T) (99.1 %), Micromonospora coxensis 2-30-b(28)(T) (99.1 %), Micromonospora aurantiaca DSM 43813(T) (98.8 %) and Micromonospora chalcea DSM 43026(T) (98.7 %). However, a combination of DNA-DNA hybridization results and phenotypic properties indicated that strain SH2-13(T) ( = NBRC 107934(T) = BCC 45601(T)) should be classified as the type strain of a novel species, with the proposed name Micromonospora sediminicola sp. nov.