Actinomadura terrae sp. nov. and Actinomadura litoris OS3-89, isolated from rhizosphere soil of cactus.

Two mycelium-forming actinobacterial strains, designated OS3-83 T and OS3-89, were isolated from rhizosphere soil of a cactus (Opuntia ficus-indica) sampled on Mara Island, Jeju, Republic of Korea. Both of the isolates were found to grow at 20-37 °C, pH 6.0-10.0 and with 0-2 % (w/v) NaCl. Their taxonomic positions were investigated by a polyphasic approach. Strains OS3-83T and OS3-89 were most closely related to the type strain of Actinomadura litoris (99.5 % and 98.9 % 16S rRNA gene sequence similarity, respectively). Both of the isolates shared 99.2 % sequence similarity to each other. Morphological and chemotaxonomic characteristics supported the affiliation of the two isolates to the genus Actinomadura. 16S rRNA gene phylogeny exhibited that strain OS3-83T formed a tight cluster with A. litoris, while strain OS3-89 occupied a position located remotely from A. litoris. Nevertheless, phylogenomic analysis based on 92 core gene sequences showed that both of the isolates formed a tight clade with A. litoris. The values of average nucleotide identity and digital DNA-DNA hybridization between strain OS3-83T and the closest relative, A. litoris, were 92.2 and 46.2 %, respectively, whereas strain OS3-89 shared an average nucleotide identity value of 97.5 % and a digital DNA-DNA hybridization value of 76.9 % with A. litoris. These results strongly suggested that strain OS3-83T (=KACC 19752T=NBRC 114688T) represents a novel species and strain OS3-89 (=KACC 19753=NBRC 114400) is a strain of A. litoris. On the basis of the data obtained here, strain OS3-83T is considered to represent a new species of the genus Actinomadura, for which the name Actinomadura terrae sp. nov. is proposed.

Actinomadura spongiicola sp. nov., isolated from the marine sponge Leucetta chagosensis.

A novel actinomycete strain, named LHW52907T, was isolated from a marine sponge (Leucetta chagosensis) collected in the South China Sea. The strain developed branched mycelia without fragmentation and short spore chains in hook-and- spiral form with wrinkled surfaces, bearing no more 10 spores. The cell-wall hydrolysates contained meso-diaminopimelic acid as the diagnostic diamino acid. The sugars in whole-cell hydrolysates consisted of mannose, ribose, glucose, galactose and madurose. The major fatty acids of the strain were C16 : 0, C17 : 0 and C18 : 1 ω9c. The predominant menaquinone was MK-9(H6). The strain had the highest 16S rRNA gene sequence similarity of 99.72 % to Actinomadura pelletieri DSM 43383T. However, the average nucleotide identity and in silico DNA-DNA hybridization values between them were 93.6 and 52.6 %, respectively, readily distinguishing them as two different species. The results indicate that strain LHW52907T represents a novel species of the genus Actinomadura, for which we propose the name Actinomadura spongiicola sp. nov, with the type strain LHW52907T (=DSM 106571T=CGMCC 4.7596T).

Antibacterial Spirotetronate Polyketides from an Actinomadura sp. Strain A30804.

Large scale cultivation and chemical investigation of an extract obtained from Actimonadura sp. resulted in the identification of six previously undescribed spirotetronates (pyrrolosporin B and decatromicins C-G; 7-12), along with six known congeners, namely decatromicins A-B (1-2), BE-45722B-D (3-5), and pyrrolosporin A (6). The chemical structures of compounds 1-12 were characterized via comparison with previously reported data and analysis of 1D/2D NMR and MS data. The structures of all new compounds were highly related to the spirotetronate type compounds, decatromicin and pyrrolosporin, with variations in the substituents on the pyrrole and aglycone moieties. All compounds were evaluated for antibacterial activity against the Gram-negative bacteria, Acinetobacter baumannii and Gram-positive bacteria, Staphylococcus aureus and were investigated for their cytotoxicity against the human cancer cell line A549. Of these, decatromicin B (2), BE-45722B (3), and pyrrolosporin B (7) exhibited potent antibacterial activities against both Gram-positive (MIC90 between 1-3 µM) and Gram-negative bacteria (MIC90 values ranging from 12-36 µM) with weak or no cytotoxic activity against A549 cells.

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 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.

Niclosamide Is Active In Vitro against Mycetoma Pathogens.

Redox-active drugs are the mainstay of parasite chemotherapy. To assess their repurposing potential for eumycetoma, we have tested a set of nitroheterocycles and peroxides in vitro against two isolates of Madurella mycetomatis, the main causative agent of eumycetoma in Sudan. All the tested compounds were inactive except for niclosamide, which had minimal inhibitory concentrations of around 1 µg/mL. Further tests with niclosamide and niclosamide ethanolamine demonstrated in vitro activity not only against M. mycetomatis but also against Actinomadura spp., causative agents of actinomycetoma, with minimal inhibitory concentrations below 1 µg/mL. The experimental compound MMV665807, a related salicylanilide without a nitro group, was as active as niclosamide, indicating that the antimycetomal action of niclosamide is independent of its redox chemistry (which is in agreement with the complete lack of activity in all other nitroheterocyclic drugs tested). Based on these results, we propose to further evaluate the salicylanilides, niclosamidein particular, as drug repurposing candidates for mycetoma.

Nomimicins B-D, new tetronate-class polyketides from a marine-derived actinomycete of the genus Actinomadura.

Three new tetronate-class polyketides, nomimicins B, C, and D, along with nomimicin, hereafter named nomimicin A, were isolated from the culture extract of Actinomadura sp. AKA43 collected from floating particles in the deep-sea water of Sagami Bay, Japan. The structures of nomimicins B, C, and D were elucidated through the interpretation of NMR and MS analytical data, and the absolute configuration was determined by combination of NOESY/ROESY and ECD analyses. Nomimicins B, C, and D showed antimicrobial activity against Gram-positive bacteria, Kocuria rhizophila and Bacillus subtilis, with MIC values in the range of 6.5 to 12.5 µg/mL. Nomimicins B and C also displayed cytotoxicity against P388 murine leukemia cells with IC50 values of 33 and 89 µM, respectively.

Actinomycetoma Caused by Actinomadura mexicana, A Neglected Entity in the Caribbean.

Mycetoma is a chronic infection that is slow to develop and heal. It can be caused by fungi (eumycetoma) or bacteria (actinomycetoma). We describe a case of actinomycetoma caused by Actinomadura mexicana in the Caribbean region.

Description of the bacterial RNA polymerase inhibitor GE23077-producer Actinomadura sp. NRRL B-65521T as Actinomadura lepetitiana sp. nov.

The filamentous actinomycete that produces the antibiotic GE23077 was isolated by the Lepetit Research Group from a soil sample collected in Thailand, and it was classified as a member of the genus Actinomadura on the basis of its morphology and cell-wall composition. Phylogenetic analysis based on 16S rRNA gene sequences indicated that this strain formed a distinct monophyletic line within the genus Actinomadura, and it was most closely related to Actinomadura bangladeshensis DSM 45347T (99.31 % similarity) and Actinomadura mexicana DSM 44485T (98.94 %). The GE23077-producing strain formed an extensively branched, non-fragmented vegetative mycelium; no pseudosporangia were formed and the arthrospores were organized in slightly twisted chains. The cell wall contained meso-2,6-diaminopimelic acid and the diagnostic sugar was madurose. The predominant menaquinone was MK-9(H6), with minor amounts of MK-9(H8) and MK-9(H4). The diagnostic phospholipids were phosphatidylinositol and diphosphatidylglycerol. The major cellular fatty acids were C16 : 0 and tuberculostearic acid (10-methyloctadecanoic acid), followed by minor amounts of C18:1ω9c, C16:1ω7c and 10-methylheptadecanoic acid. The genomic DNA G+C content was 71.77 mol%. Significant differences in the morphological, chemotaxonomic and biochemical data, and the low DNA-DNA relatedness between the GE23077-producing strain and closely related type strains clearly demonstrate that it represents a novel species of the genus Actinomadura, for which the name Actinomadura lepetitiana sp. nov. is proposed. The type strain is NRRL B-65521T(=LMG 31258T=DSM 109019T).

Actinomadura rubteroloni sp. nov. and Actinomadura macrotermitis sp. nov., isolated from the gut of the fungus growing-termite Macrotermes natalensis.

The taxonomic positions of two novel aerobic, Gram-positive actinobacteria, designated strains RB29T and RB68T, were determined using a polyphasic approach. Based on 16S rRNA gene sequence analysis, the closest phylogenetic neighbours of RB29T were identified as Actinomadura rayongensis DSM 102126T (99.2 % similarity) and Actinomadura atramentaria DSM 43919T (98.7 %), and for strain RB68T was Actinomadura hibisca DSM 44148T (98.3 %). Digital DNA-DNA hybridization (dDDH) between RB29T and its closest phylogenetic neighbours, A. rayongensis DSM 102126T and A. atramentaria DSM 43919T, resulted in similarity values of 53.2 % (50.6-55.9 %) and 26.4 % (24.1-28.9 %), respectively. Additionally, the average nucleotide identity (ANI) was 93.2 % (94.0 %) for A. rayongensis DSM 102126T and 82.3 % (78.9 %) for A. atramentaria DSM 43919T. dDDH analysis between strain RB68T and A. hibisca DSM 44148T gave a similarity value of 24.5 % (22.2-27.0 %). Both strains, RB29T and RB68T, revealed morphological characteristics and chemotaxonomic features typical for the genus Actinomadura, such as the presence of meso-diaminopimelic acid in the cell wall, galactose and glucose as major sugar components within whole-cell hydrolysates and the absence of mycolic acids. The major phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannoside. Predominant menaquinones were MK-9(H6) and MK-9(H8) for RB29T and MK-9(H4) and MK-9(H6) for RB68T. The main fatty acids were identified as 10-methyloctadecanoic acid (10-methyl C18:0), 14-methylpentadecanoic acid (iso-C16:0), hexadecanoic acid (C16:0) and cis-9-octadecanoic acid (C18 : 1 ω9c). Here, we propose two novel species of the genus Actinomadura: Actinomadura rubteroloni sp. nov. with the type strain RB29T (=CCUG 72668T=NRRL B-65537T) and Actinomadura macrotermitis sp. nov. with the type strain RB68T (=CCUG 72669T=NRRL B-65538T).

Actinomadura harenae sp. nov., a novel actinomycete isolated from sea sand in Sanya.

A novel actinomycete, designated strain NEAU-Ht49T, was isolated from sea sand sampled in Sanya and characterized by using a polyphasic approach. The 16S rRNA gene sequence analysis showed that strain NEAU-Ht49T was most closely related to Actinomadura rhizosphaerae SDA37T (98.8 %), Actinomadura logoneensis NEAU-G17T (98.6 %), Actinomadura oligospora ATCC 43269T (98.6 %) and Actinomadura gamaensis NEAU-Gz5T (98.6 %). The results of phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain NEAU-Ht49T formed a cluster with A. rhizosphaerae SDA37T, A. logoneensis NEAU-G17T, A. oligospora ATCC 43269T, A. gamaensis NEAU-Gz5T and Actinomadura rupiterrae CS5-AC15T (96.4 %). Meso-diaminopimelic acid was detected in its cell walls and glucose, madurose, mannose and ribose were detected in whole-cell hydrolysate. The polar lipids were found to consist of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositolmannoside and two unidentified lipids. The majoy menaquinone was MK-10(H6) and the minor menaquinones were MK-9(H4) and MK-9(H8). The major fatty acids were C16 : 0, C18 : 1ω9c, 10-methyl C18 : 0 and iso-C16 : 0. Moreover, morphological and chemotaxonomic characteristics of properties of strain NEAU-Ht49T also confirmed the affiliation of the isolate to the genus Actinomadura. However, DNA-DNA relatedness, physiological and biochemical data showed that strain NEAU-Ht49T could be distinguished from its closest relatives. Therefore, strain NEAU-Ht49T represents a novel species of the genus Actinomadura, for which the name Actinomadura harenae sp. nov. is proposed, with strain NEAU-Ht49T (=CGMCC 4.7499T=JCM 32659T) as the type strain.

Actinomadura roseirufa sp. nov., producer of semduramicin, a polyether ionophore.

The taxonomic position of 'Actinomadura roseorufa' LMG 30035T, a semduramicin-producing mutant of strain ATCC 53666P, which was isolated from a soil sample collected in Yamae Village, Kamamoto, Japan, was clarified in the present study using a polyphasic approach. This Gram-positive, aerobic actinomycete formed a well-developed, extensively branched, non-fragmenting substrate and aerial mycelia which differentiated into single, smooth-appearing spores. Based on analysis of nearly complete 16S rRNA gene sequence, strain LMG 30035T was found to be closely related to the type strains of Actinomadura fibrosa ATCC 49459T (98.88 %) and Actinomadura formosensis JCM 7474T (98.82 %) (pairwise similarity values in parentheses). Digital DNA-DNA hybridisation experiments revealed unambiguously that strain LMG 30035T represents a novel Actinomadura species (OrthoANIu values less than 83.1 %; dDDH values less than 27.2 % with type strains of validly named Actinomadura species). Analysis of the cell wall revealed the presence of meso-diaminopimelic acid in the peptidoglycan. The whole-cell sugars were glucose, madurose, galactose, ribose and rhamnose. The major polar lipids included phosphatidylinositol and diphosphatidylglycerol. The predominant menaquinones were MK-9(H6), MK-9(H8), MK-9(H4) and MK-9(H2). The major fatty acids were C16 : 00, 10-methyl C18 : 0, C18 : 1 ω9c and C18 : 00. The DNA G+C content of its genome was 72.5 mol%. In summary, these characteristics distinguish strain LMG 30035T from validly named species of the genus Actinomadura, and therefore, we propose to classify this strain formally as the novel species Actinomadura roseirufa sp. nov. with LMG 30035T (=CECT 9808T,=ATCC 53664T) as the type strain.

Actinomadura craniellae sp. nov., isolated from a marine sponge in the South China Sea.

A novel marine actinomycete, designated LHW63021T, was isolated from a marine sponge, genus Craniella, collected in the South China Sea. A polyphasic approach was applied to characterize the taxonomic position of this strain. The strain was found to have scarce aerial mycelia that differentiated into spore chains. The cell-wall hydrolysates contained meso-diaminopimelic acid as the diagnostic diamino acid. Glucose, galactose, mannose and madurose were found in the whole-cell hydrolysates. The dominant polar lipids were phosphatidylinositol and diphosphatidylglycerol. MK-9(H6) and MK-9(H8) were the predominant menaquinones. The major fatty acids were iso-C16 : 0, iso-C18 : 0, 10-methyl C17 : 0 and C18 : 1 ω9c. The DNA G+C content based on the draft genome sequence was 72.0 mol%. 16S rRNA gene sequence analysis indicated that strain LHW63021T was a member of the genus Actinomadura and had the highest similarity to Actinomadura echinospora DSM 43163T (97.3 %). Phylogenetic trees supported their close relationship. The average nucleotide identity and digital DNA-DNA hybridization values between the whole genome sequences of strain LHW63021T and A. echinospora DSM 43163T were 79.13 and 23.20 %, respectively. The evidence from the polyphasic study shows that strain LHW63021T represents a novel species of the genus Actinomadura, for which the name Actinomadura craniellae sp. nov. is proposed. The type strain is LHW63021T (=DSM 106125T=CCTCC AA 2018015T).

Actinomadura logoneensis sp. nov., a novel actinomycete isolated from the soil.

One novel actinobacterial isolate, designated strain NEAU-G17T, was isolated from muddy soil collected from a riverbank in Chad and characterised using polyphasic approach. Morphological and chemotaxonomic characteristics of this strain coincided with those of the genus Actinomadura. The 16S rRNA gene sequence analysis showed that strain NEAU-G17T was most closely related to Actinomadura oligospora JCM 10648T (98.7 %) and Actinomadura gamaensis NEAU-Gz5T (98.6 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain NEAU-G17T formed a cluster with Actinomadura oligospora JCM 10648T, Actinomadura gamaensis NEAU-Gz5T and Actinomadura rupiterrae CS5-AC15T (96.4 %). However, the combination of DNA-DNA hybridisation values and some phenotypic characteristics allowed the isolate to be differentiated from their most closely related species. The major menaquinones were identified as MK-9(H4), MK-9(H6) and MK-9(H8). Their polar lipid profile was found to contain diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside, an unidentified phospholipid and an unidentified lipid. The major fatty acids were identified as C16 : 0, iso-C16 : 0 and C18 : 1 ω9c. Therefore, it is proposed that strain NEAU-G17T should be classified as representative of a novel species of the genus Actinomadura, for which the name Actinomadura logoneensis sp. nov. is proposed. The type strains is NEAU-G17T (=CGMCC 4.7411T=DSM 105122T).

Actinomadura litoris sp. nov., an actinobacterium isolated from sandy soil in Sanya.

A novel actinobacterium, designated strain NEAU-AAG5T, was isolated from sandy soil collected from Niuwang island in Sanya, Hainan Province, PR China. The taxonomic position of the strain was investigated using a polyphasic approach. On the basis of 16S rRNA gene sequence analysis, strain NEAU-AAG5T belongs to the genus Actinomadura and shared highest sequence similarity with Actinomadura macra NBRC 14102T (98.8 %). Strain NEAU-AAG5T grows at 20-40 °C (optimum, 28 °C), pH 6-10 (optimum, pH 7) and has NaCl tolerance of 0-3 %. The menaquinones were identified as MK-9(H4) (4.2 %), MK-9(H6) (49.2 %) and MK-9(H8) (46.5 %). The major fatty acids were C16 : 0 (31.4 %), 10-methyl C18 : 0 (21.3 %) and C18 : 1 ω9c (15.7 %). The polar lipids were diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositolmannoside, phosphatidylglycerol and phosphoglycolipid. The genomic DNA G+C content of strain NEAU-AAG5T based on whole genome sequences was 72.8 mol%. Digital DNA-DNA hybridization between strain NEAU-AAG5T and its closest phylogenetic neighbour, A. macra NBRC 14102T, resulted in similarity value of 28.0 % (<70 %). Additionally, the average nucleotide identity was 84.2 % for A. macra NBRC 14102T. On the basis of phenotypic, genotypic and phylogenetic data, strain NEAU-AAG5T can be characterized to represent a novel species of the genus Actinomadura, for which the name Actinomadura litoris sp. nov. is proposed. The type strain is NEAU-AAG5T (=JCM 33456T=CCTCC AA 2019043T).

Actinomadura rhizosphaerae sp. nov., isolated from rhizosphere soil of the plant Azadirachta indica.

A novel actinomycete, strain SDA37T, belonging to the genus Actinomadura, was isolated from rhizosphere soil collected from Udon Thani Province, Thailand. The taxonomic position of the strain was characterized using a polyphasic approach. Meso-diaminopimelic acid, glucose, ribose, galactose and madurose were detected in cell-wall and whole-cell hydrolysates. The N-acyl type of muramic acid was acetyl. Menaquinones were MK-9(H6), MK-9(H8) and MK-9(H4). The predominant cellular fatty acids were iso-C16 : 0, C16 : 0, 10-methyl C18 : 0 and iso-C14 : 0. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol and phosphatidylinositol. blast analysis of the almost-complete 16S rRNA gene sequence showed 98.8 % similarity to Actinomadura oligospora NBRC 104149T, 98.7 % similarity to Actinomadura gamaensis DSM 100815T and 97.2 % similarity to Actinomadura rupiterrae KCTC 19559T. The DNA G+C content was 73.1 mol%. Strain SDA37T showed low DNA-DNA relatedness (44.3±7.3 to 58.5±8.7 %) to A. oligospora NBRC 104149T, Actinomadura gamaensis DSM 100815T and Actinomadura rupiterrae KCTC 19559T. The new strain could also be distinguished from its closely related strains by the differences in the phenotypic characteristics. The results of taxonomic analysis suggested that strain SDA37T represented a novel species of the genus Actinomadura for which the name Actinomadura rhizosphaerae sp. nov. is proposed. The type strain is SDA37T (=KCTC 39965T=NBRC 112909T=TISTR 2523T).

Actinomadura barringtoniae sp. nov., an endophytic actinomycete isolated from the roots of Barringtonia acutangula (L.) Gaertn.

A novel actinomycete strain, designated GKU 128T, isolated from the roots of an Indian oak tree [Barringtonia acutangula (L.) Gaertn.] at Khao Khitchakut district, Chantaburi province, Thailand, was characterized by using a polyphasic approach. The strain formed a branched substrate and aerial mycelia which differentiated into straight to flexuous chains of smooth-ornamented spores. Analysis of the cell wall revealed the presence of meso-diaminopimelic acid and N-acetylmuramic acid in the peptidoglycan. The whole-cell sugars were glucose, madurose, mannose, rhamnose and ribose. Mycolic acids were absent. The major phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and phosphatidylinositolmannoside. The predominant menaquinones were MK-9(H6), MK-9(H8), MK-9(H0) and MK-9(H4). The major fatty acids were C16 : 0, C18 : 1ω9c and 10-methyl C18 : 0 (tuberculostearic acid). The genomic DNA G+C content was 70.5 mol%. Based on 16S rRNA gene sequence analysis, strain GKU 128T was closely related to the type strains of Actinomadura nitritigenes NBRC 15918T (99.2 % sequence similarity) and Actinomadura fibrosa JCM 9371T (98.7 %). The levels of DNA-DNA relatedness between strain GKU 128T and the closely related type species were less than 19 %. On the basis of phenotypic and genotypic characteristics, strain GKU 128T could be distinguished from its closely related type strains and represents a novel species of the genus Actinomadura, for which the name Actinomadura barringtoniae sp. nov. (=TBRC 7225T=NBRC 113074T) is proposed.

Natalenamides A⁻C, Cyclic Tripeptides from the Termite-Associated Actinomadura sp. RB99.

In recent years, investigations into the biochemistry of insect-associated bacteria have increased. When combined with analytical dereplication processes, these studies provide a powerful strategy to identify structurally and/or biologically novel compounds. Non-ribosomally synthesized cyclic peptides have a broad bioactivity spectrum with high medicinal potential. Here, we report the discovery of three new cyclic tripeptides: natalenamides A⁻C (compounds 1⁻3). These compounds were identified from the culture broth of the fungus-growing termite-associated Actinomadura sp. RB99 using a liquid chromatography (LC)/ultraviolet (UV)/mass spectrometry (MS)-based dereplication method. Chemical structures of the new compounds (1⁻3) were established by analysis of comprehensive spectroscopic methods, including one-dimensional (¹H and 13C) and two-dimensional (¹H-¹H-COSY, HSQC, HMBC) nuclear magnetic resonance spectroscopy (NMR), together with high-resolution electrospray ionization mass spectrometry (HR-ESIMS) data. The absolute configurations of the new compounds were elucidated using Marfey's analysis. Through several bioactivity tests for the tripeptides, we found that compound 3 exhibited significant inhibitory effects on 3-isobutyl-1-methylxanthine (IBMX)-induced melanin production. The effect of compound 3 was similar to that of kojic acid, a compound extensively used as a cosmetic material with a skin-whitening effect.

Structure elucidation and in silico docking studies of a novel furopyrimidine antibiotics synthesized by endolithic bacterium Actinomadura sp. AL2.

On screening of endolithic actinobacteria from a granite rock sample of Meghalaya for antibacterial compound, a novel antibacterial compound CCp1 was isolated from the fermentation broth of Actinomadura sp. AL2. On purification of the compound based on chromatographic techniques followed by characterization with FT-IR, UV-visible, 1H NMR, 13C NMR and mass spectrometry, the molecular formula of the compound was generated as C20H17N3O2, a furopyrimidine derivative. In vitro antibacterial activity of the compound was evaluated against both Gram positive and negative bacteria by agar well diffusion assay. The compound had lowest MIC (2.00 µg/ml) for Bacillus subtilis and highest MIC (> 64 µg/ml) for Staphylococcus epidermidis and Pseudomonas aeruginosa. The study revealed that the compound has potential antibacterial activity. The mode of action of the antibacterial compound was evaluated through in silico studies for its ability to bind DNA gyrase, 30S RNA molecules, OmpF porins and N-Acetylglucosamine-1-phosphate uridyltransferase (GlmU). The antibacterial compound demonstrated more favorable docking with DNA gyrase, 30S RNA molecules and OmpF porins than GlmU which support the antibacterial compound CCp1 can be as a promising broad spectrum antibiotic agent with "multitarget" characteristics.

Actinomadura adrarensis sp. nov., an actinobacterium isolated from Saharan soil.

A novel actinobacterial strain, designated ACD12T, was isolated from a Saharan soil sample collected from Adrar province, southern Algeria. A polyphasic study was carried out to establish the taxonomic position of this strain. Strain ACD12T was observed to form extensively branched substrate mycelia. Aerial mycelium was absent or was weakly produced on all media tested, while spore chains were short with a hooked and irregular spiral form (2-3 turns). The dominant diaminopimelic acid isomer in the cell wall was meso-diaminopimelic acid. Glucose, ribose, galactose, mannose and madurose occured in whole-cell hydrolysates. The major phospholipid was diphosphatidylglycerol and phosphatidylinositol. The predominant menaquinone was MK-9(H6). The fatty acid profile was characterized by the presence of C16 : 0, C17 : 0, C15 : 0, C18 : 0, C18 : 1 cis9 and iso-C16 : 0. Results of 16S rRNA gene sequence comparisons revealed that strain ACD12T shared the highest degree of 16S rRNA gene sequence similarity with Actinomadura sputi DSM 45233T (98.3 %) and Actinomadura hallensis DSM 45043T (97.8 %). All tree-making algorithms used also supported strain ACD12T forming a distinct clade with its most closely related species. In addition, DNA-DNA hybridization indicated only 39.8 % relatedness with A. sputi DSM 45233T and 18.7 % relatedness with A. hallensis DSM 45043T. The combined phenotypic and genotypic data show that the novel isolate represents a novel species of the genus Actinomadura, for which the name Actinomadura adrarensis sp. nov., is proposed, with the type strain ACD12T (=DSM 46745T =CECT 8842T).