Species Of Micromonospora Research Articles

Micromonospora cathayae sp. nov., isolated from the rhizosphere soil of Cathaya argyrophylla.

A novel actinobacterium, strain HUAS 3T, was isolated from the rhizosphere soil of Cathaya argyrophylla collected in Hunan Province, PR China. Strain HUAS 3T contained meso-diaminopimelic acid in the cell-wall peptidoglycan. The dominant menaquinones were MK-9(H4), MK-9(H6), MK-10(H2) and MK-9(H4). The polar lipids consisted of diphosphatidylglycerol, phospholipids, phosphatidylethanolamine, phosphatidylglycerol, phosphotidylinositol and phosphatidylinositol mannosides. The main cellular fatty acids (>5.0 %) were C17 : 1 ω8c, iso-C16 : 0, C18 : 1 ω9c, iso-C15 : 0, C16 : 0 and summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c). The DNA G+C content of the novel strain's genome sequence, consisting of 7 196 442 bp, was 72.8 mol%. The full-length 16S rRNA gene sequence analysis indicated that strain HUAS 3T belonged to the genus Micromonospora and showed highest similarities to Micromonospora fluminis A38T (99.44 %), Micromonospora echinospora DSM 43816T (99.23 %), Micromonospora tulbaghiae DSM 45142T (99.23 %), Micromonospora solifontis PPF5-17T (99.16 %) and Micromonospora endolithica DSM 44398T (98.96 %). Phylogenetic trees based on 16S rRNA gene sequences showed that strain HUAS 3T was closely related to M. fluminis A38T, M. tulbaghiae DSM 45142T and M. solifontis PPF5-17T. The phylogenomic tree revealed that strain HUAS 3T was closely related to Micromonospora pallida DSM 43817T. However, the average nucleotide identity (ANIb/ANIm) and the digital DNA-DNA hybridization values between them were 84.75 /88.16 and 30.80 %, respectively, far less than the 95-96 and 70 % cut-off points recommended for delineating species. Furthermore, strain HUAS 3T was distinct from the type strain of M. pallida in terms of phenotypic and chemotaxonomic characteristics. In summary, strain HUAS 3T represents a novel Micromonospora species, for which the name Micromonospora cathayae sp. nov. is proposed. The type strain is HUAS 3T (=MCCC 1K08599T=JCM 36275T).

Unveiling growth-promoting attributes of peanut root endophyte Micromonospora sp.

In this study, 20 endophytic actinobacteria were isolated from different parts of peanut plants growing in cropland with low and high salt in West Bengal, India. The endophytes underwent a rigorous morphological, biochemical, and genetic screening process to evaluate their effectiveness in enhancing plant growth. About 20% of these isolates were identified as potential plant growth-promoting endophytic actinobacteria, which showed high 16S rRNA gene sequence similarity (up to 99-100%) with different species of Micromonospora. Among these isolates, Micromonospora sp. ASENR15 produced the highest levels of indole acetic acid (IAA) and gibberellic acid (GA), while Micromonospora sp. ASENL2, Micromonospora sp. ANENR4, and Micromonospora sp. ASENR12 produced the highest level of siderophore. Among these leaf and root endophytic Micromonospora, strain ANENR4 was tested for its plant growth-promoting attributes. ANENR4 can be transmitted into the roots of a healthy peanut plant, enhances growth, and colonize the roots in abundance, suggesting the potential agricultural significance of the strain. Moreover, the study is the first report of endophytic Micromonospora in peanuts with PGP effects. The outcomes of this study open avenues for further research on harnessing the benefits of this endophytic Micromonospora for optimizing plant growth in agriculture.

Micromonospora parastrephiae sp. nov. and Micromonospora tarensis sp. nov., isolated from the rhizosphere of a Parastrephia quadrangularis plant growing in the Salar de Tara region of the Central Andes in Chile.

Two novel Micromonospora strains, STR1-7T and STR1S-6T, were isolated from the rhizosphere of a Parastrephia quadrangularis plant growing in the Salar de Tara region of the Atacama Desert, Chile. Chemotaxonomic, cultural and phenotypic features confirmed that the isolates belonged to the genus Micromonospora. They grew from 20 to 37 °C, from pH7 to 8 and in the presence of up to 3 %, w/v NaCl. The isolates formed distinct branches in Micromonospora gene trees based on 16S rRNA gene sequences and on a multi-locus sequence analysis of conserved house-keeping genes. A phylogenomic tree generated from the draft genomes of the isolates and their closest phylogenetic neighbours showed that isolate STR1-7T is most closely related to Micromonospora orduensis S2509T, and isolate STR1S-6 T forms a distinct branch that is most closely related to 12 validly named Micromonospora species, including Micromonospora saelicesensis the earliest proposed member of the group. The isolates were separated from one another and from their closest phylogenomic neighbours using a combination of chemotaxonomic, genomic and phenotypic features, and by low average nucleotide index and digital DNA-DNA hybridization values. Consequently, it is proposed that isolates STR1-7T and STR1S-6T be recognized as representing new species in the genus Micromonospora, namely as Micromonospora parastrephiae sp. nov. and Micromonospora tarensis sp. nov.; the type strains are STR1-7T (=CECT 9665T=LMG 30768T) and STR1S-6T (=CECT 9666T=LMG 30770T), respectively. Genome mining showed that the isolates have the capacity to produce novel specialized metabolites, notably antibiotics and compounds that promote plant growth, as well as a broad-range of stress-related genes that provide an insight into how they cope with harsh abiotic conditions that prevail in high-altitude Atacama Desert soils.

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

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

Exploring Micromonospora as Phocoenamicins Producers.

Over the past few years, new technological and scientific advances have reinforced the field of natural product discovery. The spirotetronate class of natural products has recently grown with the discovery of phocoenamicins, natural actinomycete derived compounds that possess different antibiotic activities. Exploring the MEDINA's strain collection, 27 actinomycete strains, including three marine-derived and 24 terrestrial strains, were identified as possible phocoenamicins producers and their taxonomic identification by 16S rDNA sequencing showed that they all belong to the Micromonospora genus. Using an OSMAC approach, all the strains were cultivated in 10 different media each, resulting in 270 fermentations, whose extracts were analyzed by LC-HRMS and subjected to High-throughput screening (HTS) against methicillin-resistant Staphylococcus aureus (MRSA), Mycobacterium tuberculosis H37Ra and Mycobacterium bovis. The combination of LC-UV-HRMS analyses, metabolomics analysis and molecular networking (GNPS) revealed that they produce several related spirotetronates not disclosed before. Variations in the culture media were identified as the most determining factor for phocoenamicin production and the best producer strains and media were established. Herein, we reported the chemically diverse production and metabolic profiling of Micromonospora sp. strains, including the known phocoenamicins and maklamicin, reported for the first time as being related to this family of compounds, as well as the bioactivity of their crude extracts. Although our findings do not confirm previous statements about phocoenamicins production only in unique marine environments, they have identified marine-derived Micromonospora species as the best producers of phocoenamicins in terms of both the abundance in their extracts of some major members of the structural class and the variety of molecular structures produced.

Micromonospora antibiotica sp. nov. and Micromonospora humidisoli sp. nov., two new actinobacterial species exhibiting antimicrobial potential.

Two novel actinobacterial strains, designated MMS20-R2-23T and MMS20-R2-29T, were isolated from riverside soil and subjected to taxonomic characterization. Both strains were Gram-stain-positive, aerobic, non-motile and filamentous, and formed orange to strong orange-brown coloured colonies, which later turned black. Both strains grew optimally at mesophilic temperatures, neutral to slightly alkaline pH and in the absence of NaCl. Analysis of 16S rRNA gene sequences indicated that the two novel strains fell into phylogenetic clusters belonging to the genus Micromonospora. Strains MMS20-R2-23T and MMS20-R2-29T showed the highest 16S rRNA gene sequence similarity to Micromonospora phytophila SG15T (99.3 %) and Micromonospora humida MMS20-R1-14T (99.4 %), respectively. Based on the comparative genome analysis, strain MMS20-R2-23T had the highest orthologous average nucleotide identity (orthoANI) value of 92.70 % with Micromonospora matsumotoense DSM 44100T, and MMS20-R2-29T shared 94.99 % with Micromonospora wenchangensis CCTCC AA 2012002T. Besides, the digital DNA-DNA hybridization (dDDH) values of MMS20-R2-23T and MMS20-R2-29T with the same species were 47.6 and 59.2% respectively, which were also highest among the compared species, thus confirming the separation of each strain at species level from related species. The orthoANI and dDDH values between MMS20-R2-23T and MMS20-R2-29T were 92.18 and 44.9% respectively. The genomes of strains MMS20-R2-23T and MMS20-R2-29T were estimated as 7.56 Mbp and 7.13 Mbp in size, and the DNA G+C contents were 72.5 and 72.9 mol%, respectively. The chemotaxonomic properties of both strains were consistent with those of the genus. The novel strains showed antimicrobial activity against a broad range of microbes, in particular Gram-positive bacteria and yeasts. It is evident that each of the isolated strains merits recognition as representing novel species of Micromonospora, for which the names Micromonospora antibiotica sp. nov. (type strain=MMS20-R2-23T=KCTC 49542T=JCM 34495T) and Micromonospora humidisoli sp. nov. (type strain=MMS20-R2-29T=KCTC 49543T=JCM 34496T) are proposed.

Phylogenetic Characterization and Detection of Polyketide Synthase Type I and Non-ribosomal Peptide Synthases Genes in Micromonospora Strains Isolated from Chilean Marine Sediments

There has been an increasing emphasis on the need to exploit un- and underexplored environments especially the marine environments for microbial and chemical diversity. Previous in-depth exploration of Chilean marine sediments have led to the isolation of members of the Micromonosporaceae, which require de-replication and characterization to establish taxonomic status along with screening of the isolates for the ability to produce bioactive compounds. This study was, therefore, embarked on with the aim of assessing phylogenetic relationship of the isolates and screening for novel polyketide synthases type I (PKS-I), non-ribosomal peptide synthases (NRPS) biosynthetic genes (BGC). This involved culture, de-replication by the traditional colour grouping to select representative strains, amplification of 16S rRNA, PKS-I and NRPS genes, sequencing and phylogenetic analysis. Thirty-four representative strains were selected from 66 Micromonospora species. Following the 16S rRNA gene sequence analysis, 11 belonged to the genus Micromonospora, 7 strains residing in the genera Exiguobacterium and Bacillus. The phylogenetic analysis of the 16S rRNA gene sequences of the strains inferred that these strains are novel members of this sub-order. The partial sequences of PKS-I and NRPS genes amplified from eight Micromonospora strains, produced matches with a variety of BGCs including Streptomyces noursei, S. neyagawaensis concanamycin A and Streptomyces sp. heptaene macrolide complex synthesis gene cluster. There exists an untapped microbial diversity in the Chilean marine sediments with great potential of been exploited for novel bioactive compounds as the search for newer and more potent natural products deepens.

Yield improvement of enediyne yangpumicins in Micromonospora yangpuensis through ribosome engineering and fermentation optimization.

Yangpumicins (YPMs), for example, YPM A, F, and G, are newly discovered enediynes from Micromonospora yangpuensis DSM 45577, which could be exploited as promising payloads of antibody-drug conjugates. However, the low yield of YPMs in the wild-type strain (∼1mg L-1 ) significantly hampers their further drug development. In this study, a combined ribosome engineering and fermentation optimization strategy has been used for yield improvement of YPMs. One gentamicin-resistant M. yangpuensis DSM 45577 strain (MY-G-1) showed higher YPMs production (7.4± 1.0mg L-1 ), while it exhibits delayed sporulation and slender mycelium under scanning electron microscopy. Whole genome re-sequencing of MY-G-1 reveals several deletion and single nucleotide polymorphism mutations, which were confirmed by PCR and DNA sequencing. Further Box-Behnken experiment and regression analysis determined that the optimal medium concentrations of soluble starch, D-mannitol, and pharmamedia for YPMs production in shaking flasks (10.0± 0.8mg L-1 ). Finally, the total titer of YPM A/F/G in MY-G-1 reached to 15.0± 2.5mg L-1 in 3 L fermenters, which was about 11-fold higher than the original titer of 1.3± 0.3mg L-1 in wild-type strain. Our study may be instrumental to develop YPMs into a clinical anticancer drug, and inspire the use of these multifaceted strategies for yield improvement in Micromonospora species. GRAPHICAL ABSTRACT LAY SUMMARY: ???

Micromonospora rubida sp. nov., a novel actinobacterium isolated from soil of Harbin.

A novel actinobacterium, designated strain NEAU-HG-1T, was isolated from soil collected from Harbin, Heilongjiang Province, Northeast China and characterised using a polyphasic approach. On the basis of 16S rRNA gene sequence analysis, strain NEAU-HG-1T belonged to the genus Micromonospora, and shared high sequence similarities with Micromonospora auratinigra DSM 44815T (98.9%) and Micromonospora coerulea DSM 43143T (98.7%). Morphological and chemotaxonomic characteristics of the strain also supported its assignment to the genus Micromonospora. Cell wall contained meso-diaminopimelic acid and the whole-cell sugars were arabinose and xylose. The polar lipid contained diphosphatidylglycerol, phosphatidylethanolamine, glycolipid and phosphatidylinositol. The predominant menaquinones were MK-10(H2), MK-10(H4) and MK-10(H6). The major fatty acids were C17:0 cycle, iso-C15:0, and iso-C16:0. Furthermore, strain NEAU-HG-1T displayed a DNA-DNA relatedness of 33.8 ± 2.2% with M. coerulea DSM 43143T. The level of digital DNA-DNA hybridization between strain NEAU-HG-1T and M. auratinigra DSM 44815T was 27.2% (24.8-29.7%). The value was well below the criteria for species delineation of 70% for dDDH. Whole-genome average nucleotide identity analyses result also indicated that the isolate should be assigned to a new species under the genus Micromonospora. Therefore, it is concluded that strain NEAU-HG-1T represents a novel species of the genus Micromonospora, for which the name Micromonospora rubida sp. nov. is proposed, with NEAU-HG-1T (= CGMCC 4.7479T = JCM 32386T) as the type strain.

Micromonospora species from rarely-exploited Egyptian habitats: chemical profile, antimicrobial, and antitumor activities through antioxidant property.

The development of new anticancer agents with a selective action mechanism has become a significant scientific challenge, especially as cancers remain the world's leading cause of death. Actinobacteria and its bioactive compounds have recently become a promising perspective alternative to cancer therapy. In this study, some extracted metabolites of Micromonospora exhibited potent antimicrobial with microbial inhibition zone ≥ 7 mm, and cytotoxic activities against MCF-7 and HepG2 cell lines with promising activities ≥ 85%. Additionally, treatment of DENA/CCl4 rats with the strain Micromonospora sp1 has induced a substantial amelioration of the liver functions, enhancing liver architecture near normal and antioxidant properties through elevation of antioxidant enzyme levels. So that these preliminary results can provide metabolites from Micromonospora sp1 as an anti-liver cancer therapy. Finally, we introduced the chemical profiling of Micromonospora sp1 metabolic extract by LC-QTOF-MS-MS technique, where eight compounds with reported antioxidant property anti-liver cancer activity were targeted, validated as iNOS inhibitor through molecular docking studies. The findings in this study can be a significant step towards studying natural bioactive products produced by Micromonospora spp. as agents for anti-liver cancer. KEY POINTS: • Metabolites of Micromonospora strain from unexploited Egyptian habitats were investigated with LC/MS library-based chemical profile and molecular docking studies as iNOS inhibitors. • Some Micromonospora strains exhibited potent antimicrobial with microbial inhibition zone ≥ 7 mm, and cytotoxic activities against MCF-7 and HepG2 cell lines with promising activities ≥ 85%. • Micromonospora extract exhibited anti-liver cancer activity in vivo through the antioxidant property by inhibiting the liver cancer biomarkers (LDH and AFP) and enhancing other biochemical parameters.

Exploring the Potential of Antibiotic Production From Rare Actinobacteria by Whole-Genome Sequencing and Guided MS/MS Analysis.

Actinobacteria are well recognized for their production of structurally diverse bioactive secondary metabolites, but the rare actinobacterial genera have been underexploited for such potential. To search for new sources of active compounds, an experiment combining genomic analysis and tandem mass spectrometry (MS/MS) screening was designed to isolate and characterize actinobacterial strains from a mangrove environment in Macau. Fourteen actinobacterial strains were isolated from the collected samples. Partial 16S sequences indicated that they were from six genera, including Brevibacterium, Curtobacterium, Kineococcus, Micromonospora, Mycobacterium, and Streptomyces. The isolate sp.01 showing 99.28% sequence similarity with a reference rare actinobacterial species Micromonospora aurantiaca ATCC 27029T was selected for whole genome sequencing. Organization of its gene clusters for secondary metabolite biosynthesis revealed 21 clusters encoded to antibiotic production, which is higher than other Micromonospora species. Of the genome-predicted antibiotics, kanamycin was found through guided MS/MS analysis producible by the M. aurantiaca strain for the first time. The present study highlighted that genomic analysis combined with MS/MS screening is a promising method to discover potential of antibiotic production from rare actinobacteria.

Characterisation of anti-pseudomonad activity of hyper-arid Micromonospora species

The opportunistic pathogen Pseudomonas aeruginosa is a major cause of nosocomial infections, and has been categorised by the World Health Organisation as a “Priority 1: Critical” target for research and development of novel antibiotics owing to its intrinsic multi-resistance and ability to acquire novel resistance mechanisms. One strategy for discovering novel antibiotics is the identification and characterisation of metabolites with antimicrobial activity. Members of the bacterial phylum Actinobacteria are historic source of these metabolites, in particular the genus Streptomyces. However, other genera have not received this same level of interest despite sharing the capacity to biosynthesise a diverse array of metabolites. One such genus is Micromonospora, responsible for production of the broad-spectrum aminoglycoside antibiotic gentamicin (M. purpurea). Here we present three Micromonospora species isolated from the Atacama Desert, Chile; that possess anti-pseudomonad bioactivity inducible by culture on International Streptomyces Project (ISP) Media. In addition, preliminary data indicates that this activity can be affected by the addition of P. aeruginosa conditioned media. In parallel, short-read Illumina sequencing was used to assemble draft genomes for these strains, enabling antiSMASH analysis of putative biosynthetic gene clusters. In addition to this, estimated Average Nucleotide Identity (ANI) as calculated by the autoMLST server indicates that these strains may all be novel Micromonospora species. The results of this work serve to highlight the biosynthetic capacity of an understudied genus of bacteria, as well as the value of examining underexplored environments and habitats in the search for novel bioactive molecules.

Actinomycetes from the Red Sea Sponge Coscinoderma mathewsi: Isolation, Diversity, and Potential for Bioactive Compounds Discovery.

The diversity of actinomycetes associated with the marine sponge Coscinoderma mathewsi collected from Hurghada (Egypt) was studied. Twenty-three actinomycetes were separated and identified based on the 16S rDNA gene sequence analysis. Out of them, three isolates were classified as novel species of the genera Micromonospora, Nocardia, and Gordonia. Genome sequencing of actinomycete strains has revealed many silent biosynthetic gene clusters and has shown their exceptional capacity for the production of secondary metabolites, not observed under classical cultivation conditions. Therefore, the effect of mycolic-acid-containing bacteria or mycolic acid on the biosynthesis of cryptic natural products was investigated. Sponge-derived actinomycete Micromonospora sp. UA17 was co-cultured using liquid fermentation with two mycolic acid-containing actinomycetes (Gordonia sp. UA19 and Nocardia sp. UA 23), or supplemented with pure mycolic acid. LC-HRESIMS data were analyzed to compare natural production across all crude extracts. Micromonospora sp. UA17 was rich with isotetracenone, indolocarbazole, and anthracycline analogs. Some co-culture extracts showed metabolites such as a chlorocardicin, neocopiamycin A, and chicamycin B that were not found in the respective monocultures, suggesting a mycolic acid effect on the induction of cryptic natural product biosynthetic pathways. The antibacterial, antifungal, and antiparasitic activities for the different cultures extracts were also tested.

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).

Secondary Metabolites from Marine Micromonospora: Chemistry and Bioactivities.

Marine Micromonospora was revealed to be a rather untapped and a rich source of chemically diverse and unique bioactive natural products. This review is aimed to make a comprehensive survey of secondary metabolites that were derived from marine Micromonospora including chemical diversity and biological activities. A total of 116 compounds from 41 marine Micromonospora species have been reported, covering the literatures from 1997 to 2019. These compounds contain several structural classes such as polyketides (PKS), nonribosomal peptides (NRPS), PKS-NRPS hybrids, terpenes and others, and they present cytotoxic, antibacterial, antiparasitic, chemopreventive or antioxidant activities.

Genome Sequence of Micromonospora terminaliae TMS7T, a New Endophytic Actinobacterium Isolated from the Medicinal Plant Terminalia mucronata.

Micromonospora terminaliae sp. nov., type strain TMS7T, is a gram-positive nonmotile aerobic actinobacterium that was recently isolated from a surface-sterilized stem of the medicinal plant Terminalia mucronata. This strain was described as a novel species in the Micromonospora genus. To elucidate the application potential of this species, its genome was completely sequenced, using the PacBio SMRT cell platform, and was compared with selected complete genome sequences of other Micromonospora species. Genomic analysis revealed that the genome of TMS7T consists of one circular DNA chromosome of 6,717,200 bp with a GC content of 73.35% and one plasmid of 24,912 bp with a GC content of 65.39%. The entire genome contains 6,311 predicted coding genes, 57 transfer RNAs, and nine ribosomal RNA genes. The genome contains a type III polyketide biosynthesis gene cluster, which encodes enzymes that catalyze the production of alkyl-O-dihydrogeranyl-methoxyhydroquinone. This information combined with the previous report that this strain can grow well on pH 10 medium with 4% NaCl (wt/vol) indicates that this strain may have potential biocontrol applications for economic plants cultivated on alkaline soil.

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.

Isolation of bacteria at different points of Pleurotus ostreatus cultivation and their influence in mycelial growth

Pleurotus ostreatus is one of the most cultivated edible mushrooms worldwide and few approaches have been done to analyze bacterial influence during its cultivation. Therefore, bacteria from commercial spawn, mycelial-colonized straw and fruiting bodies from healthy productive samples were counted, isolated and tested for their mycelial growth promoting ability. Bacterial cell numbers at different steps of the process showed low bacterial cell numbers in spawn and in fruiting bodies inner tissue compared to the high concentration in mycelial-colonized straw. The majority of the 38 isolates belonged to phyla Firmicutes and Actinobacteria were identified as Bacillus, Paenibacillus and Micromonospora species. Similarly, 16S rRNA gene bacterial clones obtained from mycelial biomass DNA samples showed bacterial presence of various genera including Bacillus and Paenibacillus.In the mycelial growth promoting ability tests, 30 isolates negatively affected mycelial growth, two isolates showed no effect on mycelial growth, and six isolates promoted mycelial growth. Moreover, mycelial thickness was influenced in different ways by the bacterial growth. In general, nearly all isolates growth-preventing were isolated from healthy spawn and mycelial-colonized straw, whereas fruiting bodies were the best source for isolation of mycelial growth-promoting bacteria. Characterization of bacterial isolates revealed that growth-preventing isolates exhibited various enzymatic activities in comparison with positive influencing bacteria that exhibited none or weak enzymatic activities. In addition, the influence of volatile compounds being present in the headspace of bi-plate co-cultures on P. ostreatus mycelial growth was demonstrated.The effect of isolates, that promoted mycelial growth in co-cultivation, to reduce P. ostreatus spawn running time, was evaluated on sterilized rye seeds. Results showed that not all mycelial promoted isolates were able to significantly promote P. ostreatus colonization. However, isolate M46F identified as Micromonospora lupini significantly reduce spawn running time. This is one of few studies to estimate cultivable bacteria from healthy samples of P. ostreatus cultivation, to evaluate a bacterial effect on mycelial growth, to show that fruiting bodies are a good source for mycelia growth-promoting isolates, and the first to report a shorter P. ostreatus spawn running time due to bacterial inoculation.

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).