Description of Streptomyces siderophoricus sp. nov., a promising nocardamine-producing species isolated from the rhizosphere soil of Mangifera indica.

An actinomycete, designated strain CH9-7T, was isolated from the rhizosphere soil of Mangifera indica. The morphological and chemotaxonomic properties, such as the production of spiral spore chains and the presence of LL-diaminopimelic acid in the peptidoglycan, showed that it belongs to the genus Streptomyces. Based on the 16S rRNA gene analysis, it was confirmed that strain CH9-7T was a member of the genus Streptomyces and revealed 99.9% 16S rRNA gene sequence similarity to its closest relative strains, Streptomyces lydicus NBRC 13058 T and Streptomyces chattanoogensis NBRC 12754 T. Although the strain showed high 16S rRNA gene sequence similarity values, however, genome relatedness indexes exhibited that the average nucleotide identity based on the MUMmer (ANIm) algorithm, the average amino acid identity (AAI), and the digital DNA-DNA hybridization values between strain CH9-7T and its closest phylogenomic relatives were below the threshold values for delineation of a novel species, (ANIm ranging from 87.5 to 88.6, AAI ranging from 80.6 to 84.6, and dDDH ranging from 28.4 to 31.7), respectively. A taxonomic position of strain CH9-7T in the phylogenomic tree showed that the closest relative strain was S. lydicus NBRC 13058 T. The comparative phenotypic studies between strain CH9-7T and its closest relatives revealed that strain CH9-7T could be classified as a novel species of the genus Streptomyces. Thus, the name Streptomyces siderophoricus sp. nov. is proposed for the strain. The type strain is CH9-7T ( = TBRC 17833 T = NBRC 116426 T). The chemical investigation led to the isolation of four known compounds (compounds 1-4). Among these compounds, compound 1 was identified to be nocardamine, a promising bioactive substance.

Pradimicin U, a promising antimicrobial agent isolated from a newly found Nonomuraea composti sp. nov.

Pradimicin U is a new dihydrobenzo[a]naphthacenequinone compound found to be active on a screen designed to investigate compounds with antimicrobial activity, produced by the actinomycete designated strain FMUSA5-5T. The strain was isolated from a bio-fertilizer of Musa spp. collected from Suphanburi province, Thailand. The chemotaxonomic characteristics and 16S rRNA gene analysis revealed that strain FMUSA5-5T is a member of the genus Nonomuraea. Low genome-based taxonomic criteria, average nucleotide identity (ANI) (82.8-88.3%), average amino-acid identity (AAI) (79.4-87.3%), and digital DNA-DNA hybridization (dDDH) (29.5-38.5%) values and several phenotypic differences between strain FMUSA5-5T and its closest type strains of the genus Nonomuraea indicated that strain FMUSA5-5T represents a novel species of the genus Nonomuraea and the name Nonomuraea composti sp. nov. is proposed for the strain. The crude extract from the culture broth of strain FMUSA5-5T displayed promising antimicrobial activity against several pathogens and led to the isolation of a novel secondary metabolite, pradimicin U. Interestingly, this compound displayed a broad spectrum of biological activities such as antimalarial activity against Plasmodium falciparum K1 (IC50 value = 3.65 µg/mL), anti-Mycobacterium tuberculosis H37Ra (MIC value = 25.0 µg/mL), anti-Alternaria brassicicola BCC 42724 (MIC value = 25.0 µg/mL), anti-Bacillus cereus ATCC 11778 and anti-Staphylococcus aureus ATCC 29213 (MIC values = 6.25 and 1.56 µg/mL, respectively). Moreover, the compound possessed strong anti-human small cell lung cancer (NCI-H187) activity with IC50 value of 5.69 µg/mL, while cytotoxicity against human breast cancer (MCF-7) and Vero cells was very weak (IC50 values of 52.49 and 21.84 µg/mL, respectively).

Fructose promotes pyoluteorin biosynthesis via the CbrAB-CrcZ-Hfq/Crc pathway in the biocontrol strain Pseudomonas PA1201.

Biocontrol strain Pseudomonas PA1201 produces pyoluteorin (Plt), which is an antimicrobial secondary metabolite. Plt represents a promising candidate pesticide due to its broad-spectrum antifungal and antibacterial activity. Although PA1201 contains a complete genetic cluster for Plt biosynthesis, it fails to produce detectable level of Plt when grown in media typically used for Pseudomonas strains. In this study, minimum medium (MM) was found to favor Plt biosynthesis. Using the medium M, which contains all the salts of MM medium except for mannitol, as a basal medium, we compared 10 carbon sources for their ability to promote Plt biosynthesis. Fructose, mannitol, and glycerol promoted Plt biosynthesis, with fructose being the most effective carbon source. Glucose or succinic acid had no significant effect on Plt biosynthesis, but effectively antagonized fructose-dependent synthesis of Plt. Promoter-lacZ fusion reporter strains demonstrated that fructose acted through activation of the pltLABCDEFG (pltL) operon but had no effect on other genes of plt gene cluster; glucose or succinic acid antagonized fructose-dependent pltL induction. Mechanistically, fructose-mediated Plt synthesis involved carbon catabolism repression. The two-component system CbrA/CbrB and small RNA catabolite repression control Z (crcZ) were essential for fructose-induced Plt synthesis. The small RNA binding protein Hfq and Crc negatively regulated fructose-induced Plt. Taken together, this study provides a new model of fructose-dependent Plt production in PA1201 that can help improve Plt yield by biosynthetic approaches.

Streptomyces zingiberis sp. nov., an endophytic actinobacterium isolated from the root tissue of Zingiber montanum.

An endophytic actinobacterium, designated strain PLAI 1-29T, was isolated from the root tissue of Zingiber montanum collected from Pathum Thani province, Thailand. Strain PLAI 1-29T was characterized using a polyphasic taxonomic approach. It typically exhibited morphological and chemotaxonomic properties of the genus Streptomyces. Strain PLAI 1-29T produced a spiral spore chain on aerial mycelium and grew at 15-40 °C, pH 6-10 on International Streptomyces Project 2 agar. The maximum NaCl concentration for growth was 9 % (w/v). Cells of strain PLAI 1-29T presented ll-diaminopimelic acid, arabinose, galactose and ribose. The detected phospholipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannoside. The major menaquinones were MK-9(H6) and MK-9(H8). The major cellular fatty acids were iso-C16 : 0, anteiso-C15 : 0 and anteiso-C17 : 0. The genome-based taxonomic details revealed the assignment of strain PLAI 1-29T to the genus Streptomyces and exhibited low threshold values for the delineation of a novel species by average nucleotide identity-blast (84.0%), average amino acid identity (80.0%) and digital DNA-DNA hybridization (27.6%) with its closest type strain, Streptomyces xinghaiensis S187T. Furthermore, several differential physiological and biochemical characteristics were detected between strain PLAI 1-29T and the closest type strain. Based on the combined phenotypic and genomic features, strain PLAI 1-29T (=TBRC 7645T=NBRC 113170T) is considered to represent a new Streptomyces species, for which we propose the name Streptomyces zingiberis sp. nov.

Micromonospora solifontis sp. nov., an actinobacterium isolated from hot spring soil.

An actinobacterium strain, PPF5-17T, was isolated from hot spring soil collected from Chiang Rai province, Thailand. The strain exhibited morphological and chemotaxonomic properties similar to those of members of the genus Micromonospora. Colonies of PPF5-17T were strong pinkish red and turned black after sporulation in ISP 2 agar medium. Cells formed single spores directly on the substrate mycelium. Growth was observed from 15 to 45 °C and at pH 5-8. Maximum NaCl concentration for growth was 3 % (w/v). PPF5-17T was found to have meso-diaminopimelic acid, xylose, mannose and glucose in the whole-cell hydrolysate. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositolmannosides were observed as the membrane phospholipids. MK-10(H6), MK-9(H6), MK-10(H4) and MK-9(H4) were the major menaquinones. The predominant cellular fatty acids were iso-C15 : 0, iso-C17 : 0, anteiso-C17 : 0 and iso-C16 : 0. PPF5-17T shared the highest 16S rRNA gene sequence similarity with Micromonospora fluminis LMG 30467T (99.3 %). A genome-based taxonomic study revealed that PPF5-17T was closely related to Micromonospora aurantinigra DSM 44815T in the phylogenomic tree with an average nucleotide identity by blast (ANIb) of 87.7 % and a digital DNA-DNA hybridization (dDDH) value of, 36.1 % which were below the threshold values for delineation of a novel species. Moreover, PPF5-17T could be distinguished from its closest neighbours, M. fluminis LMG 30467T and M. aurantinigra DSM 44815T, with respect to a broad range of phenotypic properties. Thus, PPF5-17T represents a novel species, for which the name Micromonospora solifontis sp. nov. is proposed. The type strain is PPF5-17T (= TBRC 8478T = NBRC 113441T).

Streptomyces telluris sp. nov., a promising terrestrial actinobacterium with antioxidative potentials.

An actinomycete strain, AA8T, which produced a long straight chain of spores (verticillati type), was isolated from the rhizosphere soil of Mangifera indica in Bangkok, Thailand. A polyphasic taxonomic study was carried out to establish the taxonomic position of the strain. Strain AA8T formed a tight taxonomic position in the 16S rRNA gene tree with Streptomyces roseifaciens MBT76T. In contrast, the genome-based taxonomic analysis showed that strain AA8T shared low average nucleotide identity-BLAST (94.1%), the digital DNA-DNA hybridization (58.2%), and the average amino acid identity (93.6%) values with S. roseifaciens MBT76T. Moreover, a combination of physiological and biochemical properties indicated that strain AA8T was distinguished from all Streptomyces species with effectively published names. Strain AA8T, therefore, represents a novel species of Streptomyces, and the name Streptomyces telluris is proposed for the strain. The type strain is AA8T (= TBRC 8483T = NBRC 113461T). The chemical investigation led to the isolation of nine known compounds (compounds 1-9). Among these compounds, compound 7 (3,4-dihydroxybenzaldehyde) possesses strong antioxidant activity equal to ascorbic acid, a powerful antioxidative agent.

Streptomyces salinarius sp. nov., an actinomycete isolated from solar saltern soil.

An actinobacterium, designated strain SS06011T, was isolated from solar saltern soil collected from Samut Sakhon province, Thailand. The taxonomic position of this strain was established using the polyphasic taxonomic approach. The strain produced grey aerial spore mass on International Streptomyces Project 2 seawater agar that differentiated into spiral spore chains with rugose-surfaced spores. Strain SS06011T was found to have ll-diaminopimelic acid in the cell peptidoglycan. Whole-cell hydrolysates contained galactose, glucose and ribose. MK-9(H6) and MK-9(H4) were major menaquinones. The major cellular fatty acids comprised iso-C16 : 0, anteiso-C15 : 0 and anteiso-C17 : 0. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylinositol were detected in cells. These characteristics were coincident with the typical morphological and chemotaxonomic properties of the genus Streptomyces. The taxonomic affiliation at the genus level of this strain could also be confirmed by its 16S rRNA gene sequence data. Strain SS06011T showed the highest 16S rRNA gene sequence similarity to Streptomyces ardesiacus NRRL B-1773T (99.1 %), Streptomyces coelicoflavus NBRC 15399T (99.1 %) and Streptomyces hyderabadensis OU-40T (99.1 %). Digital DNA-DNA hybridization (dDDH), average nucleotide identity-blast (ANIb) and average amino acid identity (AAI) values between strain SS06011T and its closely related type strains, S. ardesiacus NBRC 15402T, S. coelicoflavus NBRC 15399T and S. hyderabadensis JCM 17657T, were in the range of 45.4-48.4 % (for dDDH), 90.8-91.9 % (for ANIb) and 90.8-91.7 % (for AAI), respectively, which are lower than the cut-off criteria for species delineation. The DNA G+C content of genomic DNA was 71.9 mol%. With the differences in physiological, biochemical and genotypic data, strain SS06011T could be discriminated from its closest neighbours. Thus, strain SS06011T should be recognized as representing a novel species of the genus Streptomyces, for which the name Streptomyces salinarius sp. nov. is proposed. The type strain is SS06011T (=TBRC 9951T=NBRC 113998T).

Gordonia aquimaris sp. nov., a novel marine actinobacterium isolated from seawater in the upper gulf of Thailand.

An actinobacterium strain, SW21T, was isolated from seawater collected in the upper Gulf of Thailand. Cells were Gram-stain-positive, aerobic and rod-shaped. Growth was observed from 15 to 37 °C and at pH 6-8. Maximum NaCl for growth was 14 % (w/v). meso-Diaminopimelic acid, arabinose, galactose, glucose, rhamnose and ribose were detected in the whole-cell hydrolysate. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannoside were detected as the phospholipids in the cells. The major menaquinones were MK-9(H2) and MK-7(H2). The major cellular fatty acids were C16 : 0, C18 : 1 ω9c, C18 : 0 and C18 : 010-methyl (TBSA). The 16S rRNA gene sequence data supported the assignment of strain SW21T to the genus Gordonia and showed that Gordonia mangrovi KCTC 49383T (98.7 %) was the closest relative. Moreover, the average nucleotide identity-blast (85.5 %) and digital DNA-DNA hybridization (30.7 %) values between strain SW21T and its closest neighbour were below the threshold values for delineation of a novel species. The combination of genotypic and phenotypic data indicated that strain SW21T is representative of novel species of the genus Gordonia. The name Gordonia aquimaris sp. nov. is proposed for strain SW21T. The type strain is SW21T (=TBRC 15691T=NBRC 115558T).

New insights into the neuroprotective and beta-secretase1 inhibitor profiles of tirandamycin B isolated from a newly found Streptomyces composti sp. nov.

Tirandamycin (TAM B) is a tetramic acid antibiotic discovered to be active on a screen designed to find compounds with neuroprotective activity. The producing strain, SBST2-5T, is an actinobacterium that was isolated from wastewater treatment bio-sludge compost collected from Suphanburi province, Thailand. Taxonomic characterization based on a polyphasic approach indicates that strain SBST2-5T is a member of the genus Streptomyces and shows low average nucleotide identity (ANI) (81.7%), average amino-acid identity (AAI) (78.5%), and digital DNA-DNA hybridization (dDDH) (25.9%) values to its closest relative, Streptomyces thermoviolaceus NBRC 13905T, values that are significantly below the suggested cut-off values for the species delineation, indicating that strain SBST2-5T could be considered to represent a novel species of the genus Streptomyces. The analysis of secondary metabolites biosynthetic gene clusters (smBGCs) in its genome and chemical investigation led to the isolation of TAM B. Interestingly, TAM B at 20 µg/mL displayed a suppressive effect on beta-secretase 1 (BACE1) with 68.69 ± 8.84% inhibition. Molecular docking simulation reveals the interaction mechanism between TAM B and BACE1 that TAM B was buried in the pocket of BACE-1 by interacting with amino acids Thr231, Asp 228, Gln73, Lys 107 via hydrogen bond and Leu30, Tyr71, Phe108, Ile118 via hydrophobic interaction, indicating that TAM B represents a potential active BACE1 inhibitor. Moreover, TAM B can protect the neuron cells significantly (% neuron viability = 83.10 ± 9.83% and 112.72 ± 6.83%) from oxidative stress induced by serum deprivation and Aß1-42 administration models at 1 ng/mL, respectively, without neurotoxicity on murine P19-derived neuron cells nor cytotoxicity against Vero cells. This study was reportedly the first study to show the neuroprotective and BACE1 inhibitory activities of TAM B.

Micromonospora thermarum sp. nov., an actinobacterium isolated from hot spring soil.

An actinomycete, designated strain HSS6-12T, was isolated from hot spring sediment collected from Ranong province, Thailand. The strain showed taxonomic characteristics consistent with those of members of the genus Micromonospora. HSS6-12T produced a single spore directly on the substrate mycelium, and no aerial mycelium was detected. The isomer of diamino acid presented in cell wall peptidoglycan was meso-diaminopimelic acid. Arabinose, xylose, glucose, and ribose were detected in whole-cell hydrolysates. MK-10(H4), MK-9(H4), and MK-10(H6) were major menaquinones. Major cellular fatty acids were iso-C16:0, iso-C15:0, and iso-C17:0. Phospholipid profile was composed of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, and phosphatidylinositolmannosides. 16S rRNA gene analysis revealed that HSS6-12T shared the highest 16S rRNA gene sequence similarity with Micromonospora inositola DSM 43819T (99.3%). In contrast, the genome analysis showed that HSS6-12T formed a tight taxonomic position in a phylogenomic tree with Micromonospora endolithica DSM 44398T. Moreover, the average nucleotide identity-blast, the digital DNA-DNA hybridization, and the average amino acid identity values between HSS6-12T and M. inositola DSM 43819T and M. endolithica DSM 44398T were 83.1-84.0%, 27.5-28.7%, and 80.4-82.2%, respectively, indicating that HSS6-12T was different species with both closely related Micromonospora-type strains. In addition, HSS6-12T could be discriminated from its closely related type strains by many physiological and biochemical characteristics. Thus, HSS6-12T could be considered a novel species of the genus Micromonospora, and the name Micromonospora thermarum is proposed for the strain. The type strain is HSS6-12T (= BCC 41915T = JCM 17127T).

Antimalarial and antimicrobial substances isolated from the endophytic actinomycete, Streptomyces aculeolatus MS1-6.

Seven undescribed compounds, including four naphthoquinone terpenoids (aculeolatins A - D), one rare 2-nitropyrrole terpenoid (nitropyrrolin F), and two hydroxamate siderophores (aculeolamides A and B) and one further undescribed compound (2,5,7-trihydroxy-3,6-dimethylnaphthalene-1,4-dione), together with eleven known compounds (arromycin, phenaziterpene A, nitropyrrolin A, heronapyrroles A and B, salaceyin A, 5,7-dihydroxy-2-isopropylchromone, 1-hydroxyphenazine, 1-methoxyphenazine, 1-acetyl-ß-carboline, and N-(2-phenylethyl) acetamide), were isolated from the cultures of the endophytic Streptomyces aculeolatus MS1-6. The structures of the isolated compounds were determined using NMR spectroscopy and corroborated using chemical modification. These compounds exhibited a broad spectrum of biological activities, including antimalarial (IC50 6.03-9.84 µg/mL), antitubercular (MIC 3.13-6.25 µg/mL), anti-plant pathogenic fungal (MIC 25.0-50.0 µg/mL), and antibacterial (MIC 3.03-50 µg/mL) activities; however, they displayed unremarkable cytotoxicity against cancerous (MCF-7 and NCI-H187) and non-cancerous (Vero) cell lines.

Streptomyces sennicomposti sp. nov., an actinomycete isolated from compost of Senna siamea (Lam.).

A member of the genus Streptomyces, designated RCPT1-4T, was isolated from compost of Senna siamea (Lam.), collected from an agricultural area in Rayong province, Thailand. The spore morphology and the presence of ll-diaminopimelic acid in the peptidoglycan indicate that RCPT1-4T shows the typical properties of members of the genus Streptomyces. On the basis of the results of 16S rRNA gene sequence analysis, the strain should be classified as representing a member of the genus Streptomyces and was most closely related to Streptomyces fumigatiscleroticus NBRC 12999T with the highest 16S rRNA gene sequence similarity of 99.2 %, followed by Streptomyces spiralis NBRC 14215T (99.0 %). In addition, RCPT1-4T shared the highest average nucleotide identity by blast (ANIb) (86.0 %), and digital DNA-DNA hybridization (dDDH) (32.1 %) values with S. spiralis NBRC 14215T. Furthermore, several physiological and biochemical differences were observed between RCPT1-4T and the closely related type strains of species with validly published names. These taxonomic data indicated that RCPT1-4T could be considered to represent a novel species of the genus Streptomyces and the name Streptomyces sennicomposti sp. nov. is proposed for this strain. The type strain is RCPT1-4T (=TBRC 11260T=NBRC 114303T).

Nocardia coffeae sp. nov., an endophytic actinobacterium isolated from the root of Coffea arabica (L.).

The polyphasic taxonomic study of a novel endophytic actinobacterium strain (CA2R105T) was carried out. The strain formed fragmented substrate mycelium and showed chemotaxonomic properties typical of members of the genus Nocardia, i.e. the presence of mycolic acid and MK-8 (H4ω-cycl) in its cells. Strain CA2R105T exhibited the highest 16S rRNA gene sequence similarity to Nocardia jiangxiensis NBRC 101359T (99.2%). The genome-based taxonomic analysis revealed low average nucleotide identity-blast and digital DNA-DNA hybridization values (<93.7, and <65.2%, respectively) to its closest relative. Moreover, many different phenotypic characteristics were observed between strain CA2R105T and all related Nocardia-type strains. This taxonomic evidence suggested that strain CA2R105T should be judged as representing a novel species of the genus Nocardia and the name, Nocardia coffeae sp. nov. is proposed. The type strain is CA2R105T (=TBRC 11247T=NBRC 114292T).

Streptomyces epipremni sp. nov., an endophytic actinomycete isolated from the root of Epipremnum aureum.

An endophytic Streptomyces-like micro-organism, designated strain PRB2-1T was isolated from root tissue of Epipremnum aureum (Linden and André) G.S. Bunting. The typical morphological and chemotaxonomic characteristics, i.e. the ability to produce straight spore chains directly on aerial mycelium and the presence of ll-diaminopimelic acid in cell-wall peptidoglycan, were consistent with its assignment to the genus Streptomyces. 16S rRNA gene analysis showed that strain PRB2-1T is a member of the genus Streptomyces with the highest similarity to Streptomyces bryophytorum DSM 42183T (98.4 %). Moreover, the draft genome sequence of strain PRB2-1T exhibited low average nucleotide identity by blast (79.9-83.8 %) and digital DNA-DNA hybridization (24.9-28.3 %) values to the reference strains, which were well below the species circumscription threshold. The DNA G+C content of genomic DNA was 73.6 mol%. Comparison of phenotypic characteristics and whole-genome sequence between strain PRB2-1T and its close relatives indicated that strain PRB2-1T could be classified as a novel species of the genus Streptomyces. Thus the name, Streptomyces epipremni sp. nov. is proposed for the strain. The type strain is PRB2-1T (=TBRC 7642T=NBRC 113169T).

Biological insights into the piericidin family of microbial metabolites.

Extensively produced by members of the genus Streptomyces, piericidins are a large family of microbial metabolites, which consist of main skeleton of 4-pyridinol with methylated polyketide side chain. Nonetheless, these metabolites show differences in their bioactive potentials against micro-organisms, insects and tumour cells. Due to its close structural similarity with coenzyme Q, piericidins also possess an inhibitory activity against NADH dehydrogenase as well as Photosystem II. This review studied the latest research progress of piericidins, covering the chemical structure and physical properties of newly identified members, bioactivities, biosynthetic pathway with gene clusters and future prospect. With the increasing incidence of drug-resistant human pathogen strains and cancers, this review aimed to provide clues for the development of either new potential antibiotics or anti-tumour agents.

Streptomyces acidipaludis sp. nov., an actinobacterium isolated from peat swamp forest soil.

An actinobacterium strain PLK6-54T was isolated from Lankwai peat swamp forest soil collected from Yala province, Thailand. Strain PLK6-54T exhibited morphological and chemotaxonomic properties described for the genus Streptomyces. It formed a spiral spore chain directly on aerial mycelium. Growth was observed between 20 and 40 °C and at pH 5-8. The maximum NaCl for growth was 2 % (w/v). ll-Diaminopimelic acid, arabinose and ribose were detected in the whole-cell hydrolysate. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositolmannoside were detected as the phospholipids. The major menaquinones were MK-10(H2) and MK-9(H6). The major cellular fatty acids were iso-C16 : 0, anteiso-C15 : 0 and iso-C14 : 0. 16S rRNA gene sequence data supported the assignment of strain PLK6-54T to the genus Streptomyces and showed that Streptomyces rubidus NBRC 102073T (99.0 %) was the closest relative. Moreover, the average nucleotide identity-blast (85.5 %) and digital DNA-DNA hybridization (30.7 %) values reported between strain PLK6-54T and its closest neighbour were below the threshold values for delineation of a novel species. Strain PLK6-54T could be distinguished from related validly described Streptomyces species by several phenotypic properties. The combination of genotypic and phenotypic data indicated that strain PLK6-54T is representative of a novel species of the genus Streptomyces. The name Streptomyces acidipaludis sp. nov. is proposed for strain PLK6-54T. The type strain is PLK6-54T (=TBRC 11250T=NBRC 114297T).

Nocardia acididurans sp. nov., an acid-tolerant actinobacterium isolated from bio-fertilizer of Musa species.

A novel acid-tolerant actinobacterium (strain LPG 2T), which formed fragmented substrate mycelia, was isolated from bio-fertiliser of Musa spp. collected from Lampang Province, Thailand. Its morphological and chemotaxonomic properties, e.g., the presence of mycolic acid and MK-8 (H4ω-cycl) in the cells, showed that strain LPG 2T was a member of the genus Nocardia. 16S rRNA gene sequence analysis revealed that this strain was closely related to Nocardia otitidiscaviarum NBRC 14405T (98.7 %). The low average nucleotide identity-blast and digital DNA-DNA hybridization values (<78.6 and <24.0 %, respectively), and several phenotypic differences between strain LPG 2T and its related Nocardia type strains, indicated that the strain merits classification as representing a novel species of the genus Nocardia, for which we propose the name Nocardia acididurans sp. nov. The type strain is LPG 2T (=TBRC 11242T=NBRC 114293T).

H-NS family protein MvaU downregulates phenazine-1-carboxylic acid (PCA) biosynthesis via binding to an AT-rich region within the promoter of the phz2 gene cluster in the rhizobacterium Pseudomonas strain PA1201.

Histone-like nucleoid-structuring (H-NS) proteins are key regulators in gene expression silencing and in nucleoid compaction. The H-NS family member proteins MvaU in Pseudomonas aeruginosa are thought to bind the same AT-rich regions of chromosomes and function to coordinate the control of a common set of genes. Here, we explored the molecular mechanism by which MvaU controls PCA biosynthesis in P. aeruginosa PA1201. We present evidence suggesting that MvaU is self-regulated. Deletion of mvaU significantly increased PCA production, and PCA production sharply decreased when mvaU was over-expressed. MvaU transcriptionally repressed phz2 cluster expression and consequently reduced PCA biosynthesis. ß-galactosidase assays confirmed that base pairing near the -35 box is required when MvaU regulates PCA production in PA1201. Electrophoretic mobility shift assays (EMSA) and additional point mutation analysis demonstrated that MvaU directly bound to an AT-rich motif within the promoter of the phz2 cluster. Chromatin immunoprecipitation (ChIP) analysis also indicated that MvaU directly bound to the P5 region of the phz2 cluster promoter. MvaU repression of PCA biosynthesis was independent of QscR and OxyR in PA1201 and neither PCA or H2O2 were the environmental signals that induced mvaU expression. These findings detail a new MvaU-dependent regulatory pathway of PCA biosynthesis in PA1201 and provide a foundation to increase PCA fermentation titer by genetic engineering.

Streptomyces endocoffeicus sp. nov., an endophytic actinomycete isolated from Coffea arabica (L.).

An aerobic, non-motile, Gram-stain positive actinomycete, designated strain CA3R110T, was isolated from the surface-sterilised root of Coffea arabica L. collected from Lampang Province, Thailand. 16S rRNA gene sequence analysis indicated that strain CA3R110T was a member of the genus Streptomyces and showed the closest similarities to Streptomyces buecherae AC541T (99.2%), followed by Streptomyces rapamycinicus NRRL B-5491T (99.1%), Streptomyces luteoverticillatus NBRC 3840T (99.1%), Streptomyces coerulescens NBRC 12758T (99.1%), and Streptomyces iranensis HM 35T (99.0%). Strain CA3R110T contained LL-diaminopimelic acid in cell peptidoglycan, MK-9(H6), and MK-9(H8) as major menaquinone, iso-C16:0, iso-C15:0, C16:0 as major fatty acids. Diphosphatidylglycerol, phosphatidylethanolamine, hydroxy-phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositolmannoside were detected in the cell. The chemotaxonomic characteristics possessed the typical properties of the genus Streptomyces. A low digital DNA-DNA hybridization (< 55.7%) and average nucleotide identity-blast (ANIb) (< 92.2%) values revealed that strain CA3R110T could be distinguished from any known Streptomyces species. With the differences in phenotypic and genotypic data, strain CA3R110T represents a novel species of genus Streptomyces, for which the name Streptomyces endocoffeicus sp. nov. is proposed. The type strain is CA3R110T (= TBRC 11245T = NBRC 114296T).

Streptomyces musisoli sp. nov., an actinomycete isolated from soil.

An actinobacterium, strain CH5-8T, which formed spiral chains of spore arising from the aerial mycelium, was isolated from rhizosphere soil of Musa spp. The organism exhibited vivid greenish yellow substrate mycelium and easily produced the medium grey aerial spore mass on ISP2 medium. The typical chemotaxonomic properties of members of the genus Streptomyces were observed for strain CH5-8T, e.g. ll-diaminopimelic acid in cell peptidoglycan, MK-9(H8), MK-9(H6), and MK-9(H4) as major menaquinones and anteiso-C15 : 0, iso-C16 : 0, and anteiso-C17 : 0 as major fatty acids. Diphosphatidylglycerol, phosphatidylethanolamine, hydroxyphosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannoside were detected in the cells. A combination of morphological and chemotaxonomic data supported the assignment to the genus Streptomyces. The analysis result obtained for the 16S rRNA gene sequence confirmed the taxonomic affiliation at the genus level of this strain. The novel strain CH5-8T showed the highest 16S rRNA gene sequence values to Streptomyces echinatus NBRC 12763T (98.9 %), followed by Streptomyces actinomycinicus RCU-197T (98.9 %). The average nucleotide identity by blast (ANIb) and digital DNA-DNA hybridization values between CH5-8T and its closest relatives, S. echinatus CECT 3313T and S. actinomycinicus RCU-197T, were ≤91.6 % and ≤47.4 %, respectively. The digital DNA G+C content of genomic DNA was 72.1 mol%. On the basis of these phenotypic and genotypic data, strain CH5-8T represents a novel species, for which the name Streptomyces musisoli sp. nov. is proposed. The type strain is CH5-8T (=TBRC 9950T=NBRC 113997T).