Micromonospora humida sp. nov., exhibiting antimicrobial potential, isolated from riverside soil.

An actinobacterial strain designated MMS20-R1-14T was isolated from a riverside soil sample. Colonies on agar plates were orange to strong orange brown in colour, which later became black. The cells grew at 10-40 °C (optimum, 37 °C), pH 5.0-11.0 (pH 8.0) and in the presence of 0-4 % NaCl (1 %). The 16S rRNA gene sequence of strain MMS20-R1-14T showed highest similarities to Micromonospora wenchangensis CCTCC AA 2012002T (99.51 %) and Micromonospora rifamycinica AM105T (99.37 %). The orthoANI values between strain MMS20-R1-14T and the two type strains were 95.72 and 90.99 %, and the digital DNA-DNA hybridization values were 63.6 and 40.8 %, respectively, thus confirming the distinction of strain MMS20-R1-14T from its mostly related species. The DNA G+C content of strain MMS20-R1-14T was 72.9 mol%. The strain contained meso-diaminopimelic acid as the major cell-wall amino acid, and the characteristic whole-cell sugars were arabinose, xylose, glucose, ribose and rhamnose. The main cellular fatty acids were C18 : 1 ω9c, iso-C15 : 0 and iso-C16 : 0, the diagnostic polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine, and the predominant menaquinones were MK-10(H4) and MK-10(H6), all of which were consistent with those of Micromonospora. Strain MMS20-R1-14T showed antimicrobial activity against a range of bacterial and yeast species. The genome of the strain was found to contain 33 potential biosynthetic gene clusters for secondary metabolites, thus showing a high potential as a producer of bioactive compounds. On the basis of these phenotypic, genotypic and chemotaxonomic data, strain MMS20-R1-14T merits recognition as representing a novel species of the genus Micromonospora, for which the name Micromonospora humida sp. nov. (type strain=MMS20 R1-14T=KCTC 49541T=JCM 34494T) is proposed.

Micromonospora tarapacensis sp. nov., a bacterium isolated from a hypersaline lake.

Strain Llam7T was isolated from microbial mat samples from the hypersaline lake Salar de Llamará, located in Taracapá region in the hyper-arid core of the Atacama Desert (Chile). Phenotypic, chemotaxonomic and genomic traits were studied. Phylogenetic analyses based on 16S rRNA gene sequences assigned the strain to the family Micromonosporaceae with affiliation to the genera Micromonospora and Salinispora. Major fatty acids were C17 : 1ω8c, iso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0. The cell walls contained meso-diaminopimelic acid and ll-2,6 diaminopimelic acid (ll-DAP), while major whole-cell sugars were glucose, mannose, xylose and ribose. The major menaquinones were MK-9(H4) and MK-9(H6). As polar lipids phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol and several unidentified lipids, i.e. two glycolipids, one aminolipid, three phospholipids, one aminoglycolipid and one phosphoglycolipid, were detected. Genome sequencing revealed a genome size of 6.894 Mb and a DNA G+C content of 71.4 mol%. Phylogenetic analyses with complete genome sequences positioned strain Llam7T within the family Micromonosporaceae forming a distinct cluster with Micromonospora (former Xiangella) phaseoli DSM 45730T. This cluster is related to Micromonospora pelagivivens KJ-029T, Micromonospora craterilacus NA12T, and Micromonospora craniellae LHW63014T as well as to all members of the former genera Verrucosispora and Jishengella, which were re-classified as members of the genus Micromonospora, forming a clade distinct from the genus Salinispora. Pairwise whole genome average nucleotide identity (ANI) values, digital DNA-DNA hybridization (dDDH) values, the presence of the diamino acid ll-DAP, and the composition of whole sugars and polar lipids indicate that Llam7T represents a novel species, for which the name Micromonospora tarapacensis sp. nov. is proposed, with Llam7T (=DSM 109510T,=LMG 31023T) as the type strain.

Micromonospora veneta sp. nov., an endophytic actinobacterium with potential for nitrogen fixation and for bioremediation.

Strain CAP181T, an endophytic actinobacterium, was isolated from a surface sterilized root sample of a native pine tree, Flinders University, Adelaide, South Australia. Chemotaxonomic data including cell wall components, major fatty acids, and major menaquinones confirmed the affiliation of strain CAP181T to the genus Micromonospora. This strain was Gram stain positive with well-developed substrate mycelia to form a single spore with hairy surface. The phylogenetic tree showed that M. coerulea NBRC 13504 T is the closest phylogenetic neighbour, sharing 99.2% 16S rRNA gene similarity and the next closest neighbor is M. chaiyaphumensis DSM 45246 T (98.7%). Genome mining of this strain revealed genes encoding to enzymes relating to nitrogen fixation and bioremediation. Based on genotypic and phenotypic studies including DNA-DNA hybridization data, strain CAP181T was different from any of the closely related species with valid names. The name proposed for the new species is Micromonospora veneta sp. nov. The type strain is CAP181T (= DSM 109713 T = NRRL B-65535 T).

A New Micromonospora Strain with Antibiotic Activity Isolated from the Microbiome of a Mid-Atlantic Deep-Sea Sponge.

To tackle the growing problem of antibiotic resistance, it is essential to identify new bioactive compounds that are effective against resistant microbes and safe to use. Natural products and their derivatives are, and will continue to be, an important source of these molecules. Sea sponges harbour a diverse microbiome that co-exists with the sponge, and these bacterial communities produce a rich array of bioactive metabolites for protection and resource competition. For these reasons, the sponge microbiota constitutes a potential source of clinically relevant natural products. To date, efforts in bioprospecting for these compounds have focused predominantly on sponge specimens isolated from shallow water, with much still to be learned about samples from the deep sea. Here we report the isolation of a new Micromonospora strain, designated 28ISP2-46T, recovered from the microbiome of a mid-Atlantic deep-sea sponge. Whole-genome sequencing reveals the capacity of this bacterium to produce a diverse array of natural products, including kosinostatin and isoquinocycline B, which exhibit both antibiotic and antitumour properties. Both compounds were isolated from 28ISP2-46T fermentation broths and were found to be effective against a plethora of multidrug-resistant clinical isolates. This study suggests that the marine production of isoquinocyclines may be more widespread than previously supposed and demonstrates the value of targeting the deep-sea sponge microbiome as a source of novel microbial life with exploitable biosynthetic potential.

Micromonospora fluminis sp. nov., isolated from mountain river sediment.

During a bioprospection of bacteria with antimicrobial activity, the actinomycete strain A38T was isolated from a sediment sample of the Carpintero river located in the Gran Piedra Mountains, Santiago de Cuba province (Cuba). This strain was identified as a member of the genus Micromonospora by means of a polyphasic taxonomy study. Strain A38T was an aerobic Gram-positive filamentous bacterium that produced single spores in a well-developed vegetative mycelium. An aerial mycelium was absent. The cell wall contained meso-diaminopimelic acid and the whole-cell sugars were glucose, mannose, ribose and xylose. The major cellular fatty acids were isoC15:0, 10 methyl C17:0, anteiso-C17:0 and iso-C17:0. The predominant menaquinones were MK-10(H4) and MK-10(H6). Phylogenetic analysis of 16S rRNA gene sequences revealed that this strain was closely related to Micromonospora tulbaghiae DSM 45142T (99.5 %), Micromonospora citrea DSM 43903T (99.4 %), Micromonospora marina DSM 45555T (99.4 %), Micromonospora maritima DSM 45782T (99.3 %), Micromonospora sediminicola DSM 45794T (99.3 %), Micromonospora aurantiaca DSM 43813T (99.2 %) and Micromonospora chaiyaphumensis DSM 45246T (99.2 %). The results of OrthoANIu analysis showed the highest similarity to Micromonospora chalcea DSM 43026T (96.4 %). However, the 16S rRNA and gyrB gene sequence-based phylogeny and phenotypic characteristics provided support to distinguish strain A38T as a novel species. On the basis of the results presented here, we propose to classify strain A38T (=LMG 30467T=CECT 30034T) as the type strain of the novel species Micromonospora fluminis sp. nov.

Induction of Antibacterial Metabolites by Co-Cultivation of Two Red-Sea-Sponge-Associated Actinomycetes Micromonospora sp. UR56 and Actinokinespora sp. EG49.

Liquid chromatography coupled with high resolution mass spectrometry (LC-HRESMS)-assisted metabolomic profiling of two sponge-associated actinomycetes, Micromonospora sp. UR56 and Actinokineospora sp. EG49, revealed that the co-culture of these two actinomycetes induced the accumulation of metabolites that were not traced in their axenic cultures. Dereplication suggested that phenazine-derived compounds were the main induced metabolites. Hence, following large-scale co-fermentation, the major induced metabolites were isolated and structurally characterized as the already known dimethyl phenazine-1,6-dicarboxylate (1), phenazine-1,6-dicarboxylic acid mono methyl ester (phencomycin; 2), phenazine-1-carboxylic acid (tubermycin; 3), N-(2-hydroxyphenyl)-acetamide (9), and p-anisamide (10). Subsequently, the antibacterial, antibiofilm, and cytotoxic properties of these metabolites (1-3, 9, and 10) were determined in vitro. All the tested compounds except 9 showed high to moderate antibacterial and antibiofilm activities, whereas their cytotoxic effects were modest. Testing against Staphylococcus DNA gyrase-B and pyruvate kinase as possible molecular targets together with binding mode studies showed that compounds 1-3 could exert their bacterial inhibitory activities through the inhibition of both enzymes. Moreover, their structural differences, particularly the substitution at C-1 and C-6, played a crucial role in the determination of their inhibitory spectra and potency. In conclusion, the present study highlighted that microbial co-cultivation is an efficient tool for the discovery of new antimicrobial candidates and indicated phenazines as potential lead compounds for further development as antibiotic scaffold.

Micromonospora pelagivivens sp. nov., a new species of the genus Micromonospora isolated from deep-sea sediment in Japan.

A novel marine actinomycete, designated strain KJ-029T, was isolated from a marine sediment sample (water depth of 226 m) in Kagoshima, Japan. 16S rRNA gene sequence analysis revealed that the new isolate was most closely related to Micromonospora craniellae LHW 63014T (99.3 % similarity). Phylogenetic analyses of the genus Micromonospora based on 16S rRNA gene sequences showed that strain KJ-029T was clustered with Micromonospora craniellae LHW 63014T and Micromonospora endophytica 202201T. However, digital DNA-DNA hybridization analyses presented low levels of relatedness in the range of 24.8-32.9 % between strain KJ-029T and the above closely related strains. The novel strain contained meso-diaminopimelic acid and 3-OH-diaminopimelic acid, d-glutamic acid, glycine and d-alanine in the cell-wall peptidoglycan. The acyl type of the peptidoglycan was glycolyl and mycolic acids were absent. The major menaquinone was MK-9(H4). The whole-cell sugars consisted of glucose, mannose, xylose and ribose. Phosphatidylethanolamine was detected as the major phospholipid and corresponded to phospholipid type II. The predominant cellular fatty acid was iso-C16 : 0. The DNA G+C content of the genomic DNA was 71.5 mol%. Based on the present polyphasic study, strain KJ-029T represents a novel species of the genus Micromonospora, for which the name Micromonospora pelagivivens sp. nov. is proposed. The type strain is KJ-029T (=NBRC 113519T=TBRC 9233T).

Micromonospora zhangzhouensis sp. nov., a Novel Actinobacterium Isolated from Mangrove Soil, Exerts a Cytotoxic Activity in vitro.

A new bacterial strain, designated HM134T, was isolated from a sample of soil collected from a Chinese mangrove Avicennia marina forest. Assessed by a polyphasic approach, the taxonomy of strain HM134T was found to be associated with a range of phylogenetic and chemotaxonomic properties consistent with the genus Micromonospora. Phylogenetic analysis based on the 16s rRNA gene sequence indicated that strain HM134T formed a distinct lineage with the most closely related species, including M. rifamycinica AM105T, M. wenchangensis CCTCC AA 2012002T and M. mangrovi 2803GPT1-18T. The ANI values between strain HM134T and the reference strains ranged from 82.6% to 95.2%, which was below the standard criteria for classifying strains as the same species (96.5%). Strain HM134T and related species shared in silico dDDH similarities values below the recommended 70% cut-off for the delineation of species (range from 25.7-62.6%). The DNA G+C content of strain HM134T was 73.2 mol%. Analysis of phylogenetic, genomic, phenotypic and chemotaxonomic characteristics revealed that strain HM134T is considered to represent a novel species of the genus Micromonospora, for which the name M. zhangzhouensis sp. nov. is proposed. The extract of strain HM134T was demonstrated to exhibit cytotoxic activity against the human cancer cell lines HepG2, HCT-116 and A549. Active substance presented in the fermentation broth of strain HM134T was isolated by bioassay-guided analysis and purified afterwards. A new derivative of diterpenoid was identified through electrospray ionizing mass spectrometry (MS) and nuclear magnetic resonance (NMR). The compound showed different cytotoxic activities against cancer cells, with the highest cytotoxicity against HCT-116, corresponding to IC50 value of 38.4 µg/mL.

Genome-based classification of Micromonospora craterilacus sp. nov., a novel actinobacterium isolated from Nemrut Lake.

A novel actinobacterial strain, designated NA12T, was isolated from coastal sediment sample of Nemrut Lake, a crater lake in eastern Anatolia, Turkey. The taxonomic position of the strain was established using a polyphasic approach. Cultural and chemotaxonomic characteristics of the strain were consistent with its classification within the family Micromonosporaceae. The 16S rRNA gene sequence analysis of strain NA12T showed that the strain closely related to M. radicis AZ1-13T, M. zingiberis PLAI 1-1T, M. craniella LHW63014T and M. endophytica 202201T with pairwise sequence identity values ranging from 99.4 to 99.3%. Digital DNA-DNA hybridization values between strain NA12T and the closely related type strains were ranged from 41.0 to 18.3% while the average nucleotide identity values were between 87.3 and 86.5%, which are well below the designed cut-off points of 70 and 95%, respectively. The G + C content of genomic DNA was 71.5%. Whole-cell hydrolysates of strain NA12T contained 3-hydroxydiaminopimelic acid and meso-diaminopimelic acid. Cell-wall sugars were composed of arabinose, fucose, glucose, mannose, rhamnose and xylose. The polar lipid profile contained phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol, phosphatidylglycerol, glycophospholipid, amino-phospholipid and two unidentified phospholipids. The predominant menaquinones were MK-9(H6) and MK-9(H4). Major fatty acids were iso-C16:0 and C17:1ω8c. Based upon the consensus of phenotypic and phylogenetic analyses as well as whole genome comparisons, strain NA12T (DSM 100982T = KCTC 39647T) is proposed to represent the type strain of a novel species, Micromonospora craterilacus sp. nov.

Micromonospora deserti sp. nov., isolated from the Karakum Desert.

An isolate, 13K206T, with typical morphological characteristics of the genus Micromonospora was obtained during a study searching for novel actinobacteria with biosynthetic potential from the Karakum Desert. A polyphasic approach was adopted to determine taxonomic affiliation of the strain. The strain showed chemotaxonomical properties consistent with its classification in the genus Micromonospora such as meso- and 3-OH-A2pm in the cell-wall peptidoglycan, xylose in whole-cell hydrolysate and diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol as major polar lipids. The results of phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain was closely related to 'Micromonospora spongicola' S3-1T, Micromonospora nigra DSM 43818T and Micromonospora yasonensis DS3186T with sequence similarities of 98.6, 98.5 and 98.4 %, respectively. Digital DNA-DNA hybridization and average nucleotide identity analyses in addition to gyrB gene analysis confirmed the assignment of the strain to a novel species within the genus Micromonospora for which the name Micromonospora deserti sp. nov. is proposed. The type strain is 13K206T (=JCM 32583T=DSM 107532T). The DNA G+C content of the type strain is 72.4 mol%.

Micromonospora orduensis sp. nov., isolated from deep marine sediment.

A novel actinobacterial strain, designated S2509T, was isolated from marine sediment collected by a dredge at a depth of 45 m along Melet River offshore of the southern Black Sea coast, Ordu, Turkey. The cell wall peptidoglycan of strain was found to contain meso-diaminopimelic acid and 3-OH-diaminopimelic acid. The whole cell sugars detected were arabinose, glucose, rhamnose, ribose and xylose. The diagnostic phospholipids of strain S2509T were found to be diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, a glycolipid and two unidentified phospholipids. The predominant menaquinones were identified as MK-9(H8), MK-9(H6), MK-10(H8), MK-9(H4), MK-10(H4) and MK-10(H6). The major cellular fatty acids were found to be iso-C16:0, iso-C15:0 and 10-methyl C17:0. The taxonomic position of the strain was established using a polyphasic approach, showing that S2509T strain belongs to the genus Micromonospora. Phylogenetic analysis based on the 16S rRNA gene sequence of strain S2509T showed that it is closely related to the type strain of Micromonospora chokoriensis DSM 45160T (99.37% sequence similarity), and phylogenetically clustered with Micromonospora inaquosa LB39T (99.37%), Micromonospora lupini Lupac 14NT (99.16%), Micromonospora violae NEAU-zh8T (99.23%) and Micromonospora taraxaci NEAU-P5T (99.03%). The phylogenetic analysis based on the gyrB gene sequence of strain S2509T confirmed its close relationship with M. chokoriensis JCM 13247T (96.5% sequence similarity). Whole genome sequences confirmed by digital DNA-DNA hybridization analysis that the strain S2509T represents a novel species in the genus Micromonospora, for which the name Micromonospora orduensis sp. nov. is proposed. The type strain is S2509T (=DSM 45926T = KCTC 29201T).

High taxonomic diversity of Micromonospora strains isolated from Medicago sativa nodules in Western Spain and Australia.

The genus Micromonospora has been found in nodules of several legumes and some new species of this genus were isolated from these plant organs. In this study we analysed the taxonomic diversity of Micromonospora strains isolated from alfalfa nodules in Spain and Australia on the basis of three phylogenetic markers, the rrs and gyrB genes and 16S-23S intergenic spacer (ITS). The genome analysis of selected strains representative of different clusters or lineages found after rrs, gyrB and ITS analyses confirmed the results obtained with these phylogenetic markers. They showed that the analysed strains belong to at least 18 Micromonospora species including previously described ones, such as Micromonospora noduli, Micromonospora ureilytica, Micromonospora taraxaci, Micromonospora zamorensis, Micromonospora aurantiaca and Micromonospora tulbaghiae. Most of these strains belong to undescribed species of Micromonospora showing the high taxonomic diversity of strains from this genus inhabiting alfalfa nodules. Although Micromonospora strains are not able to induce the formation of these nodules, and it seems that they do not contribute to fix atmospheric nitrogen, they could play a role related with the mechanisms of plant growth promotion and pathogen protection presented by Micromonospora strains isolated from legume nodules.

Micromonospora acroterricola sp. nov., a novel actinobacterium isolated from a high altitude Atacama Desert soil.

A Micromonospora strain, designated 5R2A7T, isolated from a high altitude Atacama Desert soil was examined by using a polyphasic approach. Strain 5R2A7T was found to have morphological, chemotaxonomic and cultural characteristics typical of members of the genus Micromonospora. The cell wall contains meso- and hydroxy-diaminopimelic acid, the major whole-cell sugars are glucose, ribose and xylose, the predominant menaquinones MK-10(H4), MK-10(H6), MK-10(H8) and MK-9(H6), the major polar lipids diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and an unknown glycolipid, and the predominant cellular fatty acids iso-C16 : 0, iso-C15 : 0 and 10-methyl C17 : 0. The digital genomic DNA G+C content is 72.3 mol%. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain 5R2A7T was closely related to Micromonospora coriariae DSM 44875T (99.8 %) and Micromonospora cremea CR30T (99.7 %), and was separated readily from the latter, its closest phylogenetic neighbour, based on gyrB and multilocus sequence data, by low average nucleotide identity (92.59 %) and in silico DNA-DNA relatedness (51.7 %) values calculated from draft genome assemblies and by a range of chemotaxonomic and phenotypic properties. Consequently, strain 5R2A7T is considered to represent a novel species of Micromonospora for which the name Micromonospora acroterricola sp. nov. is proposed. The type strain is 5R2A7T (=LMG 30755T=CECT 9656T).

Micromonospora radicis sp. nov., isolated from roots of Azadirachta indica var. siamensis Valenton, and reclassification of Jishengella zingiberis as Micromonospora zingiberis comb. nov.

A novel endophytic actinomycete strain AZ1-13T was isolated from roots of Azadirachta indica, and its taxonomic position was investigated using a polyphasic approach. Pairwise 16S rRNA gene sequence similarities of strain AZ1-13T and its closest species, Jishegella zingiberis PLAI1-1T and Micromonospora endophytica 202201T, were 99.7 and 99.2 %, respectively. Phylogenetic analyses of the family Micromonosporaceae based on 16S rRNA gene sequences indicated strains AZ1-13T and J. zingiberis PLAI1-1Tare located within the genus Micromonospora. The approximate genome size of the strain was 5.96 Mb with 71.9 mol% of G+C content. The strain AZ1-13T exhibited ANIb values of 87.4 % with J. zingiberis PLAI1-1T and 85.1 % with M. endophytica 202201T. Chemotaxonomic characteristics of strain AZ1-13T were consistent within the genus Micromonospora: cell-wall peptidoglycan of the strain contained meso-diaminopimelic acid; glucose, mannose, ribose and xylose are presented as the whole-cell sugars; the predominant menaquinones were MK-9(H4) and MK-9(H6); major cellular fatty acids were iso-C15 : 0, 10-methyl C17 : 0, C17 : 0, anteiso-C17 : 0 and iso-C17 : 1ω8c; diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol were detected as distinguished phospholipids. Based on phenotypic properties, phylogeny and genomic data, the strain AZ1-13T could be distinguished from its closest neighbours, representing a novel species of the genus Micromonospora, for which the name Micromonospora radicis sp. nov. is proposed. The type strain is AZ1-13T (=KCTC 39786T=NBRC 112324T=JCM 32147T = TISTR 2404T). This study also proposed that J. zingiberisis transferred to the genus Micromonospora as Micromonospora zingiberis comb. nov. (type strain PLAI1-1T=TBRC 7644T=NBRC 113144T=JCM 32592T).

Rare actinobacteria: a potential source of bioactive polyketides and peptides.

Polyketides and peptides obtained from actinobacteria are important therapeutic compounds which include front line antibiotics and anticancer drugs. Many screening programs are directed towards isolation of bioactive compounds from these organisms but the chances of finding novel antimicrobial leads among common actinobacteria are fast dwindling. As a result, the focus has shifted to the members of less exploited genera of rare actinobacteria. Three isolates, MMS8, MMS16 and KCR3 found to be potent polyketide and peptide producers were identified by 16S rRNA gene sequencing and their sequences deposited in the GenBank under the accession numbers MG407702, MG372012 and MG430204 respectively. MMS8 identified as Micromonospora auratinigra, yielded one potent compound determined to be chloroanthraquinone with an minimum inhibitory concentration (MIC) of 8 µg/ml against Bacillus subtilis and an IC50 value of 10 µg/ml and 4 µg/ml against HeLa and IMR cell lines respectively. This is the first report of the production of chloroanthraquinone by M. auratinigra. MMS16, identified as a member of the family Micromonosporaceae, yielded a potent compound MMS16B analyzed to be a novel bafilomycin analogue. The MIC of the compound was found to be 7 µg/ml against B.subtilis and IC50 value against HeLa and IMR was observed to be 9 µg/ml and 14 µg/ml respectively. MMS16B was also found to exhibit anti-quorum sensing (AQS) activity at sublethal concentrations. KCR3 identified as Kocuria kristinae yielded a novel antimicrobial peptide with antibacterial, antifungal and AQS activity. To the best of our knowledge, no antimicrobial activity has ever been reported from K. kristinae.

Micromonospora caldifontis sp. nov., isolated from hot spring soil.

A single spore forming actinomycete, designated strain HSS6-8T, was isolated from a sample of hot spring soil. The strain had the chemotaxonomic properties consistent with its classification in the genus Micromonospora. The strain was found to have meso-diaminopimelic acid in the cell-wall peptidoglycan. The acyl type of the cell-wall muramic acid was glycolyl. The reducing sugars in the cell hydrolysates were glucose, arabinose, xylose, ribose, mannose, galactose and rhamnose. The phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphoglycolipid. The major menaquinones were MK-10(H6) and MK-10(H4). The major cellular fatty acids were iso-C16 : 0, anteiso-C17 : 0, C17 : 0 and anteiso-C15 : 0. The G+C content of the genomic DNA was 70.5 mol%. 16S rRNA gene sequence analysis revealed that strain HSS6-8T was closely related to Micromonospora nigra DSM 43818T (98.2 %), Micromonospora eburnea DSM 44814T (98.2 %) and Micromonospora spongicola S3-1T (98.1 %). The physiological and DNA-DNA hybridization data allowed the differentiation of strain HSS6-8T from its related species. Thus, the strain represents a novel species of the genus Micromonospora, for which the name Micromonospora caldifontis sp. nov. is proposed. The type strain is HSS6-8T (=TBRC 8927T=JCM 17126T).

Micromonospora craniellae sp. nov., isolated from a marine sponge, and reclassification of Jishengella endophytica as Micromonospora endophytica comb. nov.

A novel marine actinomycete, designated LHW63014T, isolated from a marine sponge, Craniella species, collected in the South China Sea, was examined using a polyphasic approach. The 16S rRNA gene sequence of strain LHW63014T showed highest similarities to Jishengella endophytica 202201T (98.9 %), Micromonospora olivasterospora DSM 43868T (98.7 %), Micromonospora maris AB-18-032T (98.6 %) and Micromonospora gifhornensis DSM 44337T (98.6 %). Phylogenetic analyses of the family Micromonosporaceae based on the 16S rRNA and gyrB gene sequences indicated that strain LHW63014T and J. endophytica 202201T located within the genus Micromonospora. Morphological and chemotaxonomic characteristics confirmed their affiliation to the genus Micromonospora. Based on phenotypic characteristics, phylogenetic data and digital DNA-DNA hybridization results, strain LHW63014T could be distinguished from its closest taxa, representing a novel species of the genus Micromonospora, for which the name Micromonospora craniellae sp. nov., is proposed, with the type strain LHW63014T (=DSM 106193T=CCTCC AA 2018012T). It is also proposed that J. endophytica be transferred to genus Micromonospora as Micromonospora endophytica comb. nov. (type strain 202201T =CGMCC 4.5597T=DSM 45430T).

Micromonospora azadirachtae sp. nov., isolated from roots of Azadirachta indica A. Juss. var. siamensis Valeton.

A Gram-stain positive actinomycete, strain AZ1-19T, isolated from roots of Azadirachta indica A. Juss. var. siamensis Valeton, collected from Chachoengsao province, Thailand, was characterised taxonomically by using a polyphasic approach. Strain AZ1-19T was found to have characteristics consistent with those of members of the genus Micromonospora. The cell wall peptidoglycan of the strain was found to contain meso-diaminopimelic acid. The predominant phospholipids were identified as diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol. The characteristic whole-cell sugars were identified as glucose, xylose, galactose and mannose. The major menaquinones were found to be MK-9(H6), MK-10(H6) and MK-10(H8), and the major cellular fatty acids were identified as iso-C16:0, iso-C15:0, anteiso-C15:0 and anteiso-C17:0. Comparative analysis of 16S rRNA gene sequences revealed that strain AZ1-19T is closely related to Micromonospora costi CS1-12T (98.75% similarity), Micromonospora avicenniae 268506T (98.75%), Micromonospora haikouensis 232617T (98.68%) and Micromonospora siamensis TT2-4T (98.61%), whilst the corresponding phylogenetic analysis based on partial gyrase subunit B (gyrB) gene sequences indicated that strain AZ1-19T forms a clade with M. avicenniae 268506T with a high bootstrap value. The DNA G + C content was determined to be 69.8 mol%. Moreover, a combination of DNA-DNA relatedness values and some phenotypic and chemotaxonomic properties indicated that the strain could be distinguished from closely related species. Therefore, it is considered that strain AZ1-19T represents a novel Micromonospora species for which the name Micromonospora azadirachtae sp. nov. is proposed. The type strain is AZ1-19T (= KCTC 39941T = NBRC 112784T = JCM 32148T = TISTR 2559T).

A study of three bacteria isolated from marine sediment and description of Micromonospora globispora sp. nov.

During a study looking for the isolation of new actinobacteria strains with potential for antibiotic production from deep marine sediment, three strains were collected with a morphology similar to the one described for the Micromonospora genus. A polyphasic study was designed to determine the taxonomic affiliation of the strains S2901T, S2903, and S2904. All the strains showed chemotaxonomic properties in line with their classification in the genus Micromonospora, meso-diaminopimelic acid in the wall peptidoglycan, a tetrahydrogenated menaquinone with nine isoprene units as major respiratory quinone, iso-C15:0 and iso-C16:0 as major fatty acids and diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol as major polar lipids. The 16S rRNA gene sequences of strain S2901T, S2903, and S2904 showed the highest similarity (99.2%) with the type strain of Micromonospora halophytica DSM 43171T, forming an independent branch in the phylogenetic gene tree. Their independent position was confirmed with gyrB gene and MLSA phylogenies. Whole genome sequences confirmed by digital DNA-DNA hybridization analysis that the isolates should be assigned to a new species within the genus Micromonospora for which the name Micromonospora globispora sp. nov. (S2901T, S2903 and S2904) is proposed.

Hunting for cultivable Micromonospora strains in soils of the Atacama Desert.

Innovative procedures were used to selectively isolate small numbers of Micromonospora strains from extreme hyper-arid and high altitude Atacama Desert soils. Micromonosporae were recognised on isolation plates by their ability to produce filamentous microcolonies that were strongly attached to the agar. Most of the isolates formed characteristic orange colonies that lacked aerial hyphae and turned black on spore formation, whereas those from the high altitude soil were dry, blue-green and covered by white aerial hyphae. The isolates were assigned to seven multi- and eleven single-membered groups based on BOX-PCR profiles. Representatives of the groups were assigned to either multi-membered clades that also contained marker strains or formed distinct phyletic lines in the Micromonospora 16S rRNA gene tree; many of the isolates were considered to be putatively novel species of Micromonospora. Most of the isolates from the high altitude soils showed activity against wild type strains of Bacillus subtilis and Pseudomonas fluorescens while those from the rhizosphere of Parastrephia quadrangulares and from the Lomas Bayas hyper-arid soil showed resistance to UV radiation.