Micromonospora tulbaghiae sp. nov., isolated from the leaves of wild garlic, Tulbaghia violacea

Unveiling the bioactive potential of Actinomycetota from the Tagus River estuary

The increase in global travel and the incorrect and excessive use of antibiotics has led to an unprecedented rise in antibiotic resistance in bacterial and fungal populations. To overcome these problems, novel bioactive natural products must be discovered, which may be found in underexplored environments, such as estuarine habitats. In the present work, estuarine actinomycetotal strains were isolated with conventional and iChip techniques from the Tagus estuary in Alcochete, Portugal, and analysed for different antimicrobial bioactivities. Extracts were produced from the isolated cultures and tested for bioactivity against Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, Aspergillus fumigatus ATCC 240305, Candida albicans ATCC 10231 and Trichophyton rubrum FF5. Furthermore, bioactive extracts were subjected to dereplication by high-performance liquid chromatography (HPLC) and high-resolution mass spectrometry (HRMS) to putatively identify their chemical components. In total, 105 isolates belonging to 3 genera were obtained. One which was isolated, MTZ3.1 T, represents a described novel taxon for which the name Streptomyces meridianus was proposed. Regarding the bioactivity testing, extracts from 12 strains proved to be active against S. aureus, 2 against E. coli, 4 against A. fumigatus, 3 against C. albicans and 10 against T. rubrum. Dereplication of bioactive extracts showed the presence of 28 known bioactive molecules, 35 hits have one or more possible matches in the DNP and 18 undescribed ones. These results showed that the isolated bacteria might be the source of new bioactive natural products.

Biotechnological and Ecological Potential of Micromonospora provocatoris sp. nov., a Gifted Strain Isolated from the Challenger Deep of the Mariana Trench

A Micromonospora strain, isolate MT25^T, was recovered from a sediment collected from the Challenger Deep of the Mariana Trench using a selective isolation procedure. The isolate produced two major metabolites, n-acetylglutaminyl glutamine amide and desferrioxamine B, the chemical structures of which were determined using 1D and 2D-NMR, including ¹H-¹⁵N HSQC and ¹H-¹⁵N HMBC 2D-NMR, as well as high resolution MS. A whole genome sequence of the strain showed the presence of ten natural product-biosynthetic gene clusters, including one responsible for the biosynthesis of desferrioxamine B. Whilst 16S rRNA gene sequence analyses showed that the isolate was most closely related to the type strain of Micromonospora chalcea, a whole genome sequence analysis revealed it to be most closely related to Micromonospora tulbaghiae 45142^T. The two strains were distinguished using a combination of genomic and phenotypic features. Based on these data, it is proposed that strain MT25^T (NCIMB 15245^T, TISTR 2834^T) be classified as Micromonospora provocatoris sp. nov. Analysis of the genome sequence of strain MT25^T (genome size 6.1 Mbp) revealed genes predicted to responsible for its adaptation to extreme environmental conditions that prevail in deep-sea sediments.

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

During a bioprospection of bacteria with antimicrobial activity, the actinomycete strain A38^T 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 A38^T 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 isoC_15:0, 10 methyl C_17:0, anteiso-C_17:0 and iso-C_17:0. 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 45142^T (99.5 %), Micromonospora citrea DSM 43903^T (99.4 %), Micromonospora marina DSM 45555^T (99.4 %), Micromonospora maritima DSM 45782^T (99.3 %), Micromonospora sediminicola DSM 45794^T (99.3 %), Micromonospora aurantiaca DSM 43813^T (99.2 %) and Micromonospora chaiyaphumensis DSM 45246^T (99.2 %). The results of OrthoANIu analysis showed the highest similarity to Micromonospora chalcea DSM 43026^T (96.4 %). However, the 16S rRNA and gyrB gene sequence-based phylogeny and phenotypic characteristics provided support to distinguish strain A38^T as a novel species. On the basis of the results presented here, we propose to classify strain A38^T (=LMG 30467^T=CECT 30034^T) as the type strain of the novel species Micromonospora fluminis sp. nov.

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

A new bacterial strain, designated HM134^T, was isolated from a sample of soil collected from a Chinese mangrove Avicennia marina forest. Assessed by a polyphasic approach, the taxonomy of strain HM134^T 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 HM134^T formed a distinct lineage with the most closely related species, including M. rifamycinica AM105^T, M. wenchangensis CCTCC AA 2012002^T and M. mangrovi 2803GPT1-18^T. The ANI values between strain HM134^T 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 HM134^T 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 HM134^T was 73.2 mol%. Analysis of phylogenetic, genomic, phenotypic and chemotaxonomic characteristics revealed that strain HM134^T 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 HM134^T 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 HM134^T 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.

Genomic Insight into Three Marine Micromonospora sp. Strains from the Gulf of California

Three actinomycete strains, designated BL1, BL4, and CV4, were isolated from sediment samples from the Gulf of California in 2009 together with nearly 300 other actinobacteria. Genome mining and analysis of their ∼6.4-Mb sequences confirmed the bioprospecting potential of these three bacteria belonging to the genus Micromonospora.

Three actinomycete strains, designated BL1, BL4, and CV4, were isolated from sediment samples from the Gulf of California in 2009 together with nearly 300 other actinobacteria. Genome mining and analysis of their ∼6.4-Mb sequences confirmed the bioprospecting potential of these three bacteria belonging to the genus Micromonospora.

Uncovering the potential of novel micromonosporae isolated from an extreme hyper-arid Atacama Desert soil

The taxonomic status, biotechnological and ecological potential of several Micromonospora strains isolated from an extreme hyper arid Atacama Desert soil were determined. Initially, a polyphasic study was undertaken to clarify the taxonomic status of five micromonosporae, strains LB4, LB19, LB32^T, LB39^T and LB41, isolated from an extreme hyper-arid soil collected from one of the driest regions of the Atacama Desert. All of the isolates were found to have chemotaxonomic, cultural and morphological properties consistent with their classification in the genus Micromonospora. Isolates LB32^T and LB39^T were distinguished from their nearest phylogenetic neighbours and proposed as new species, namely as Micromonospora arida sp. nov. and Micromonospora inaquosa sp. nov., respectively. Eluted methanol extracts of all of the isolates showed activity against a panel of bacterial and fungal indicator strains, notably against multi-drug resistant Klebsiella pneumoniae ATCC 700603 while isolates LB4 and LB41 showed pronounced anti-tumour activity against HepG2 cells. Draft genomes generated for the isolates revealed a rich source of novel biosynthetic gene clusters, some of which were unique to individual strains thereby opening up the prospect of selecting especially gifted micromonosporae for natural product discovery. Key stress-related genes detected in the genomes of all of the isolates provided an insight into how micromonosporae adapt to the harsh environmental conditions that prevail in extreme hyper-arid Atacama Desert soils.

Actinobacteria associated with stingless bees biosynthesize bioactive polyketides against bacterial pathogens

Strong activity against the bacteria Paenibacillus larvae ATCC9545, the causative agent of the American Foulbrood disease of honey bees.

Actinoplanes deserti sp. nov., isolated from a desert soil sample

A novel actinomycete, designated strain YIM CF22^T, was isolated from a desert soil sample collected from Turpan in Xinjiang Uyghur Autonomous Region, north-western China. The taxonomic position of the strain YIM CF22^T is described based on a polyphasic approach. Strain YIM CF22^T was found to form irregular sporangia on agar media. It contains meso-diaminopimelic acid in the cell wall peptidoglycan. The major menaquinone was identified as MK-9(H₄); the polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, two unidentified phospholipids and two unidentified glycolipids. The whole cell sugars were found to be ribose, mannose, galactose, glucose and xylose. The major cellular fatty acids were found to be (> 5%) iso-C_16:0 (43.5%), anteiso-C_17:0 (10.2%), iso-C_15:0 (7.1%), C_17:1 ω8c (6.3%) and iso H-C_16:1 (5.9%). The G+C content was determined to be 70.8%. 16S rRNA gene sequence analysis of strain YIM CF22^T showed high similarity (97.0%) to Actinoplanes rishiriensis NBRC 108556^T. The strain also showed high 16S rRNA gene sequence similarities to Verrucosispora sediminis CGMCC 4.3550^T (96.9%) and Micromonospora tulbaghiae DSM 45142^T (96.8%). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain YIM CF22^T clusters with A. rishiriensis NBRC 108556^T, Actinoplanes globisporus JCM 3186^T and Actinoplanes rhizophilus NEAU-A-2^T. Based on the differential phenotypic characteristics and the results of DNA-DNA relatedness and phylogenetic analysis, it is proposed that strain YIM CF22^T represents a novel species of the genus Actinoplanes, for which the name Actinoplanes deserti sp. nov. is proposed. The type strain is YIM CF22^T (= KCTC 39543^T = CCTCC AB2018113^T).

Biological Control of Mango Dieback Disease Caused by Lasiodiplodia theobromae Using Streptomycete and Non-streptomycete Actinobacteria in the United Arab Emirates

Dieback caused by the fungus Lasiodiplodia theobromae is an important disease on mango plantations in the United Arab Emirates (UAE). In this study, 53 actinobacterial isolates were obtained from mango rhizosphere soil in the UAE, of which 35 (66%) were classified as streptomycetes (SA) and 18 (34%) as non-streptomycetes (NSA). Among these isolates, 19 (12 SA and 7 NSA) showed antagonistic activities against L. theobromae associated with either the production of diffusible antifungal metabolites, extracellular cell-wall-degrading enzymes (CWDEs), or both. Using a "novel" mango fruit bioassay, all isolates were screened in vivo for their abilities to reduce lesion severity on fruits inoculated with L. theobromae. Three isolates, two belonging to Streptomyces and one to Micromonospora spp., showed the strongest inhibitory effect against this pathogen in vitro and were therefore selected for tests on mango seedlings. Our results revealed that the antifungal action of S. samsunensis UAE1 was related to antibiosis, and the production of CWDEs (i.e., chitinase) and siderophores; whilst S. cavourensis UAE1 and M. tulbaghiae UAE1 were considered to be associated with antibiotic- and CWDE-production, respectively. Pre-inoculation in greenhouse experiments with the most promising actinobacterial isolates resulted in very high levels of disease protection in mango seedlings subsequently inoculated with the pathogen. This was evident by the dramatic reduction in the estimated disease severity indices of the mango dieback of individual biocontrol agent (BCA) applications compared with the pathogen alone, confirming their potential in the management of mango dieback disease. L. theobromae-infected mango seedlings treated with S. samsunensis showed significantly reduced number of defoliated leaves and conidia counts of L. theobromae by 2- and 4-fold, respectively, in comparison to the other two BCA applications. This indicates that the synergistic antifungal effects of S. samsunensis using multiple modes of action retarded the in planta invasion of L. theobromae. This is the first report of BCA effects against L. theobromae on mango seedlings by microbial antagonists. It is also the first report of actinobacteria naturally existing in the soils of the UAE or elsewhere that show the ability to suppress the mango dieback disease.

Genome-based classification of micromonosporae with a focus on their biotechnological and ecological potential

There is a need to clarify relationships within the actinobacterial genus Micromonospora, the type genus of the family Micromonosporaceae, given its biotechnological and ecological importance. Here, draft genomes of 40 Micromonospora type strains and two non-type strains are made available through the Genomic Encyclopedia of Bacteria and Archaea project and used to generate a phylogenomic tree which showed they could be assigned to well supported phyletic lines that were not evident in corresponding trees based on single and concatenated sequences of conserved genes. DNA G+C ratios derived from genome sequences showed that corresponding data from species descriptions were imprecise. Emended descriptions include precise base composition data and approximate genome sizes of the type strains. antiSMASH analyses of the draft genomes show that micromonosporae have a previously unrealised potential to synthesize novel specialized metabolites. Close to one thousand biosynthetic gene clusters were detected, including NRPS, PKS, terpenes and siderophores clusters that were discontinuously distributed thereby opening up the prospect of prioritising gifted strains for natural product discovery. The distribution of key stress related genes provide an insight into how micromonosporae adapt to key environmental variables. Genes associated with plant interactions highlight the potential use of micromonosporae in agriculture and biotechnology.

Micromonospora phytophila sp. nov. and Micromonospora luteiviridis sp. nov., isolated as natural inhabitants of plant nodules

Two actinobacterial isolates, strains SG15T and SGB14T, were recovered through a microbial diversity study of nitrogen fixing nodules from Pisum sativum plants collected in Salamanca (Spain). The taxonomic status of these isolates was determined using a polyphasic approach and both presented chemotaxonomic and morphological properties consistent with their classification in the genus Micromonospora. For strains SG15T and SGB14T, the highest 16S rRNA gene sequence similarities were observed with Micromonospora coxensis JCM 13248T (99.2 %) and Micromonospora purpureochromogenes DSM 43821T (99.4 %), respectively. However, strains SG15T and SGB14T were readily distinguished from their phylogenetic neighbours both genetically and phenotypically indicating that they represent two new Micromonospora species. The following names are proposed for these species: Micromonosporaphytophila sp. nov. type strain SG15T (=CECT 9369T; =DSM 105363T), and Micromonosporaluteiviridis sp. nov. type strain SGB14T (=CECT 9370T; =DSM 105362T).

Micromonospora terminaliae sp. nov., an endophytic actinobacterium isolated from the surface-sterilized stem of the medicinal plant Terminalia mucronata

An endophytic actinobacterium, strain TMS7T, was isolated from the stem of a Thai medicinal plant collected from the grounds of the Phujong-Nayoa National park, Ubon Ratchathani province, Thailand. As a result of a polyphasic taxonomy study, this strain was identified as a member of the genus Micromonospora. This strain was a Gram-stain-positive, aerobic actinobacterium with well-developed substrate mycelium with hyphae forming a single microspore was non-motile. Stran TMS7T was identified according to its 16S rRNA gene sequence as a new member of the genus Micromonospora. The closest phylogenetic members sharing a similarity were Micromonospora chersina DSM 44151T at 99.4 % and Micromonospora rosaria DSM 803T, Micromonospora tulbaghiae TVU1T, Micromonospora inositola DSM 43819T and Micromonospora endolithica DSM 44398T all at 99.2 %. Chemotaxonomic data including cell wall components, major menaquinones and major fatty acids confirmed the affiliation of strain TMS7T to the genus Micromonospora. The results of the phylogenetic analysis, addition to physiological and biochemical studies in combination with DNA-DNA hybridization, allowed the genotypic and phenotypic differentiation of strain TMS7T and the most closely related species with validly published names. The name proposed for the novel species is Micromonospora terminaliae sp. nov. The type strain is TMS7T (=DSM 101760T=NRRL B-65345T).

Pharmacological Potential of Phylogenetically Diverse Actinobacteria Isolated from Deep-Sea Coral Ecosystems of the Submarine Avilés Canyon in the Cantabrian Sea

Marine Actinobacteria are emerging as an unexplored source for natural product discovery. Eighty-seven deep-sea coral reef invertebrates were collected during an oceanographic expedition at the submarine Avilés Canyon (Asturias, Spain) in a range of 1500 to 4700 m depth. From these, 18 cultivable bioactive Actinobacteria were isolated, mainly from corals, phylum Cnidaria, and some specimens of phyla Echinodermata, Porifera, Annelida, Arthropoda, Mollusca and Sipuncula. As determined by 16S rRNA sequencing and phylogenetic analyses, all isolates belong to the phylum Actinobacteria, mainly to the Streptomyces genus and also to Micromonospora, Pseudonocardia and Myceligenerans. Production of bioactive compounds of pharmacological interest was investigated by high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) techniques and subsequent database comparison. Results reveal that deep-sea isolated Actinobacteria display a wide repertoire of secondary metabolite production with a high chemical diversity. Most identified products (both diffusible and volatiles) are known by their contrasted antibiotic or antitumor activities. Bioassays with ethyl acetate extracts from isolates displayed strong antibiotic activities against a panel of important resistant clinical pathogens, including Gram-positive and Gram-negative bacteria, as well as fungi, all of them isolated at two main hospitals (HUCA and Cabueñes) from the same geographical region. The identity of the active extracts components of these producing Actinobacteria is currently being investigated, given its potential for the discovery of pharmaceuticals and other products of biotechnological interest.

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

A novel actinobacterial strain, designated DS3010T, was isolated from a Black Sea marine sediment and characterized using a polyphasic approach. The strain was shown to have chemotaxonomic, morphological and phylogenetic properties consistent with classification as representing a member of the genus Micromonospora. Comparative 16S rRNA gene sequence studies showed that the strain was most closely related to the type strains of Micromonospora saelicesensis (99.5 %), Micromonospora chokoriensis (99.4 %) and Micromonospora violae (99.3 %). Similarly, a corresponding analysis based on partial gyrB gene sequences showed that it formed a distinct phyletic branch in a subclade that included the type strains of Micromonosporazamorensis, 'Micromonospora zeae', 'Micromonospora jinlongensis', M. saelicesensis and Micromonospora lupini. DS3010T was distinguished from its closest phylogenetic neighbours by low levels of DNA-DNA relatedness and by a combination of chemotaxonomic and phenotypic properties. On the basis of these data, it is proposed that the isolate should be assigned to the genus Micromonospora as Micromonospora profundi sp. nov. with isolate DS3010T (=DSM 45981T=KCTC 29243T) as the type strain.

Micromonospora sediminis sp. nov., isolated from mangrove sediment

The novel actinomycete, strain CH3-3T, was isolated from mangrove sediment collected from Chonburi Province, Thailand. On the basis of its spore morphology and chemotaxonomic characteristics, the strain belonged to the genus Micromonospora. It contained meso-diaminopimelic acid, glucose, mannose, xylose, ribose and rhamnose in the whole-cell hydrolysate, MK-10(H4), MK-10(H6) and MK-10(H8) as major menaquinones, and iso-C15 : 0, iso-C16 : 0 and iso-C17 : 0 as major cellular fatty acids. blast analysis of 16S rRNA gene sequences revealed that the strain showed highest similarity with Micromonospora palomenae NEAU-CX1T (98.97 %) and Micromonospora coxensis 2-30-b(28)T (98.97 %). Based on phylogenetic tree analysis of the 16S rRNA gene sequence, the strain formed a cluster with M. palomenae NEAU-CX1T, Micromonospora halophytica DSM 43171T, M. coxensis 2-30-b(28)T and Micromonospora purpureochromogenes DSM 43821T. On the basis of phenotypic differences and DNA-DNA relatedness evidence, strain CH3-3T could be clearly distinguished from the closely related species of the genus Micromonospora and represents a novel species of the genus Micromonospora for which the name Micromonospora sediminis sp. nov. is proposed. The type strain is CH3-3T (=JCM 18523T=PCU 350T=TISTR 2396T).

Micromonospora yasonensis sp. nov., isolated from a Black Sea sediment

A Micromonospora strain, designated DS3186(T), isolated from sediment collected from the Black Sea off the Yason Peninsula, Ordu, Turkey, was examinated using a polyphasic approach. The strain was found to have chemotaxonomic, morphological and phylogenetic properties consistent with its clasification in the genus Micromonospora. A comparative 16S rRNA gene sequence analysis showed that the strain was closely related to the type strains of Micromonospora olivasterospora (99.0 %), Micromonospora equina (98.8 %), Micromonospora rhizosphaerae (98.8 %) and Micromonospora viridifaciens (98.8 %); low levels of DNA-DNA relatednes were found between the isolate and the M. olivasterospora and M. rhizosphaerae strains. Corresponding phylogenetic analysis based on partial gyrB gene sequences showed that strain DS3186(T) formed a subclade with the type strains of Micromonospora eburnea, M. equina, Micromonospora narathiwatensis and M. viridifaciens. Strain DS3186(T) was distinguished from its close phylogenetic neighbours using a combination of chemotaxonomic, morphological and physiological properties. Consequently, it is proposed that strain DS3186(T) represents a novel Micromonospora species for which the name Micromonospora yasonensis sp. nov. is proposed. The type strain is DS3186(T) (=DSM 45980(T) = KCTC 29433(T)).

Micromonospora endophytica sp. nov., an endophytic actinobacteria of Thai upland rice (Oryza sativa)

An actinobacterial strain, DCWR9-8-2(T), was isolated from a leaf of Thai upland rice (Oryza sativa) collected in Chumporn province, Thailand. Strain DCWR9-8-2(T) is Gram-stain-positive aerobic bacteria that produce single spores directly on the vegetative hypha. Cell wall peptidoglycan of this strain exhibits meso-diaminopimelic acid and glycine, the reducing sugars of whole-cell hydrolysate are arabinose, glucose, ribose, xylose and small amount of mannose. The phospholipid profiles in the membrane are comprised of phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides. The major menaquinones are MK-9(H4) and MK-10(H6). The diagnostic cellular fatty acids are iso-C16:0 and iso-C15:0. The G+C content of the genomic DNA is 72.5 mol%. The result of 16S rRNA sequence analysis of the strain revealed that this strain was closely related to Micromonospora auratinigra TT1-11(T) (99.25%). On the other hand, the result of gyrB gene sequence analysis revealed that this strain was closed to M. eburnea JCM 12345(T) (96.30%). In addition, a combination of DNA-DNA hybridization results and some phenotypic properties supported that this strain should be judged as a novel species of the genus Micromonospora, for which the name M. endophytica sp. nov. is proposed. The type strain is DCWR9-8-2(T) (=BCC 67267(T)=NBRC 110008(T)).

Biotechnological application and taxonomical distribution of plant growth promoting actinobacteria

Plant growth promoting (PGP) bacteria are involved in various interactions known to affect plant fitness and soil quality, thereby increasing the productivity of agriculture and stability of soil. Although the potential of actinobacteria in antibiotic production is well-investigated, their capacity to enhance plant growth is not fully surveyed. Due to the following justifications, PGP actinobacteria (PGPA) can be considered as a more promising taxonomical group of PGP bacteria: (1) high numbers of actinobacteria per gram of soil and their filamentous nature, (2) genome dedicated to the secondary metabolite production (~5 to 10 %) is distinctively more than that of other bacteria and (3) number of plant growth promoter genera reported from actinobacteria is 1.3 times higher than that of other bacteria. Mechanisms by which PGPA contribute to the plant growth by association are: (a) enhancing nutrients availability, (b) regulation of plant metabolism, (c) decreasing environmental stress, (d) control of phytopathogens and (e) improvement of soil texture. Taxonomical and chemical diversity of PGPA and their biotechnological application along with their associated challenges are summarized in this paper.

Micromonospora is a normal occupant of actinorhizal nodules

Actinorhizal plants have been found in eight genera belonging to three orders (Fagales, Rosales and Cucurbitales). These all bear root nodules inhabited by bacteria identified as the nitrogen-fixing actinobacterium Frankia. These nodules all have a peripheral cortex with enlarged cells filled with Frankia hyphae and vesicles. Isolation in pure culture has been notoriously difficult, due in a large part to the growth of fast-growing contaminants where, it was later found, Frankia was slow-growing. Many of these contaminants, which were later found to be Micromonospora, were obtained from Casuarina and Coriaria. Our study was aimed at determining if Micromonospora were also present in other actinorhizal plants. Nodules from Alnus glutinosa, Alnus viridis, Coriaria myrtifolia, Elaeagnus x ebbingei, Hippophae rhamnoides, Myrica gale and Morella pensylvanica were tested and were all found to contain Micromonospora isolates. These were found to belong to mainly three species: Micromonospora lupini, Micromonospora coriariae and Micromonospora saelicesensis. Micromonospora isolates were found to inhibit some Frankia strains and to be innocuous to other strains.

Micromonospora equina sp. nov., isolated from soil from a racecourse

Two actinomycete strains were isolated from within the fynbos-rich area surrounded by the horseracing track at Kenilworth Racecourse in Cape Town, South Africa. Rapid molecular identification indicated that the isolates belonged to the family Micromonosporaceae . Based on 16S rRNA gene sequence blast analysis, the isolates were identified as members of the genus Micromonospora . Phylogenetic analysis showed that the isolates clustered with each other and were most closely related to Micromonospora viridifaciens DSM 43909T. Further 16S rRNA gene sequence analysis using EzTaxon revealed that the isolates are closely related to Micromonospora auratinigra TT1-11T, Micromonospora chaiyaphumensis MC5-1T, Micromonospora eburnea LK2-10T, Micromonospora nigra DSM 43818T and Micromonospora olivasterospora DSM 43868T. DNA–DNA hybridization and physiological tests allowed genotypic and phenotypic differentiation of both isolates from related species; however, their high DNA–DNA relatedness showed that they belong to the same genomic species. Strain Y22T ( = DSM 45644T = NRRL B-24859T) was selected as the type strain to represent this novel species, for which the name Micromonospora equina sp. nov. is proposed.

Micromonospora cremea sp. nov. and Micromonospora zamorensis sp. nov., isolated from the rhizosphere of Pisum sativum

Three actinobacterial strains, CR30(T), CR36 and CR38(T), were isolated from rhizosphere soil of Pisum sativum plants collected in Spain. The strains were filamentous, Gram-stain-positive and produced single spores. Phylogenetic, chemotaxonomic and morphological analyses confirmed that the three strains belonged to the genus Micromonospora. 16S rRNA gene sequence analysis of strains CR30(T) and CR36 showed a close relationship to Micromonospora coriariae NAR01(T) (99.3% similarity) while strain CR38(T) had a similarity of 99.0% with Micromonospora saelicesensis Lupac 09(T). In addition, gyrB gene phylogeny clearly differentiated the novel isolates from recognized Micromonospora species. DNA-DNA hybridization, BOX-PCR and ARDRA profiles confirmed that these strains represent novel genomic species. The cell-wall peptidoglycan of strains CR30(T) and CR38(T) contained meso-diaminopimelic acid. Both strains had MK-10(H(4)) as the main menaquinone and a phospholipid type II pattern. An array of physiological tests also differentiated the isolates from their closest neighbours. Considering all the data obtained, it is proposed that strains CR30(T) and CR36 represent a novel species under the name Micromonospora cremea sp. nov. (type strain CR30(T) = CECT 7891(T) = DSM 45599(T)), whereas CR38(T) represents a second novel species, for which the name Micromonospora zamorensis sp. nov. is proposed, with CR38(T) ( = CECT 7892(T) = DSM 45600(T)) as the type strain.

Micromonospora sediminicola sp. nov., isolated from marine sediment

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

Micromonospora yangpuensis sp. nov., isolated from a sponge

An actinomycete, strain FXJ6.011T, was isolated from a cup-shaped sponge collected at Dachan reef, Yangpu in the South China Sea. The strain had morphological characteristics of members of the family Micromonosporaceae. Phylogenetic analysis of the 16S rRNA gene sequence of strain FXJ6.011T indicated the highest similarity (98.7 %) to Micromonospora auratinigra JCM 12357T, Micromonospora chaiyaphumensis JCM 12873T and Micromonospora echinofusca JCM 3327T. Analysis of the gyrB gene sequence also showed that strain FXJ6.011T should be assigned to the genus Micromonospora. It contained dd-diaminopimelic acid as the major cell-wall diamino acid and MK-10(H2) as predominant menaquinone. The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidyl mannosides and phosphatidylinositol dimannoside. The major cellular fatty acids were iso-C16 : 0, C17 : 1ω8c and C16 : 0. Physiological and biochemical data and low DNA–DNA relatedness values enabled the strain to be differentiated from members of closely related species. Based on phenotypic and genotypic data, strain FXJ6.011T represents a novel Micromonospora species, for which the name Micromonospora yangpuensis sp. nov. is proposed; the type strain is FXJ6.011T ( = CGMCC 4.5736T = NBRC 107727T).

Micromonospora humi sp. nov., isolated from peat swamp forest soil

A novel actinomycete, strain P0402T, was isolated from peat swamp forest soil collected in Thailand. Its taxonomic position was determined by using a polyphasic taxonomic approach. The chemotaxonomic characteristics of this strain matched those of the genus Micromonospora, i.e. the presence of meso-diaminopimelic acid and N-glycolyl muramic acid in the peptidoglycan, whole-cell sugar pattern D, phospholipid type II, and cellular fatty acid type 3b. Phylogenetic analysis based on 16S rRNA gene sequences revealed a close relationship between strain P0402T and Micromonospora coxensis JCM 13248T (99.0 % similarity), Micromonospora eburnea JCM 12345T (99.0 %), Micromonospora marina JCM 12870T (98.9 %), Micromonospora halophytica JCM 3125T (98.7 %), Micromonospora chalcea JCM 3031T (98.7 %), Micromonospora purpureochromogenes JCM 3156T (98.6 %) and Micromonospora aurantiaca JCM 10878T (98.5 %). It could be clearly distinguished from these type strains based on low levels of DNA–DNA relatedness and phenotypic differences. On the basis of the data presented, strain P0402T is suggested to represent a novel species of the genus Micromonospora, for which the name Micromonospora humi sp. nov. is proposed. The type strain is P0402T ( = JCM 15292T  = PCU 315T  = TISTR 1883T).