Bioprospecting of desert actinobacteria with special emphases on griseoviridin, mitomycin C and a new bacterial metabolite producing Streptomyces sp. PU-KB10-4.

BACKGROUND: Bioprospecting of actinobacteria isolated from Kubuqi desert, China for antibacterial, antifungal and cytotoxic metabolites production and their structure elucidation. RESULTS: A total of 100 actinobacteria strains were selectively isolated from Kubuqi desert, Inner Mongolia, China. The taxonomic characterization revealed Streptomyces as the predominant genus comprising 37 different species, along with the rare actinobacterial genus Lentzea. The methanolic extracts of 60.8% of strains exhibited potent antimicrobial activities against Staphylococcus aureus, Micrococcus luteus, Bacillus subtilis, Escherichia coli, Salmonella enterica, Saccharomyces cerevisiae and high to mild in vitro cytotoxicity against PC3 (prostate cancer) and A549 (lung carcinoma) cell lines. The metabolomics analysis by TLC, HPLC-UV/vis, HPLC-MS and NMR showed the presence of compounds with molecular weights ranging from 100 to 1000 Da. The scale-up fermentation of the prioritized anti-Gram-negative strain PU-KB10-4 (Streptomyces griseoviridis), yielded three pure compounds including; griseoviridin (1; 42.0 mgL- 1) with 20 fold increased production as compared to previous reports and its crystal structure as monohydrate form is herein reported for the first time, mitomycin C (2; 0.3 mgL- 1) and a new bacterial metabolite 4-hydroxycinnamide (3; 0.59 mgL- 1). CONCLUSIONS: This is the first report of the bioprospecting and exploration of actinobacteria from Kubuqi desert and the metabolite 4-hydroxycinnamide (3) is first time isolated from a bacterial source. This study demonstrated that actinobacteria from Kubuqi desert are a potential source of novel bioactive natural products. Underexplored harsh environments like the Kubuqi desert may harbor a wider diversity of actinobacteria, particularly Streptomyces, which produce unique metabolites and are an intriguing source to develop medicinally valuable natural products.

Georgenia halotolerans sp. nov., a halotolerant actinobacterium isolated from Taklamakan desert soil.

A Gram-stain-positive, aerobic, non-motile, non-spore-forming and rod-shaped actinobacterium, designated strain 10Sc9-8T, was isolated from Taklamakan desert soil sampled in the Xinjiang Uygur Autonomous Region, China. Strain 10Sc9-8T grew at 8‒37 °C (optimum, 28‒30 °C), pH 6.0‒10.0 (optimum, pH 7.0-8.0) and in the presence of 0‒15 % (w/v) NaCl (optimum, 0-3 %). Phylogenetic analysis based on 16S rRNA gene sequence suggested that strain 10Sc9-8T was affiliated with members of the genus Georgenia and showed the highest 16S rRNA gene sequence similarity to Georgenia yuyongxinii Z443T (97.4 %). Phylogenomic analysis based on the whole genome sequences indicated that strain 10Sc9-8T should be assigned into the genus Georgenia. The average nucleotide identity and digital DNA-DNA hybridization values calculated from the whole genome sequences indicated that strain 10Sc9-8T was clearly separated from other closely related species of the genus Georgenia with values below the thresholds for species delineation. Chemotaxonomic analyses showed that the cell-wall peptidoglycan was in a variant of A4α type with an interpeptide bridge comprising l-Lys-l-Ala-Gly-l-Asp. The predominant menaquinone was MK-8(H4). The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, several unidentified phospholipids, glycolipids and one unidentified lipid. The major fatty acids were anteiso-C15 : 0, anteiso-C15 : 1 A and C16 : 0. The genomic DNA G+C content was 72.7 mol%. On the basis of phenotypic, phylogenetic and phylogenomic data, strain 10Sc9-8T represents a novel species of the genus Georgenia, for which the name Georgenia halotolerans sp. nov. is proposed. The type strain is 10Sc9-8T (=JCM 33946T=CPCC 206219T).

Isolation, Structure Elucidation, and First Total Synthesis of Quinomycins K and L, Two New Octadepsipeptides from the Maowei Sea Mangrove-Derived Streptomyces sp. B475.

Mangrove actinomycetia have been proven to be one of the promising sources for discovering novel bioactive natural products. Quinomycins K (1) and L (2), two rare quinomycin-type octadepsipeptides without intra-peptide disulfide or thioacetal bridges, were investigated from the Maowei Sea mangrove-derived Streptomyces sp. B475. Their chemical structures, including the absolute configurations of their amino acids, were elucidated by a combination of NMR and tandem MS analysis, electronic circular dichroism (ECD) calculation, advanced Marfey's method, and further unequivocally confirmed by the first total synthesis. The two compounds displayed no potent antibacterial activity against 37 bacterial pathogens and had no significant cytotoxic activity against H460 lung cancer cells.

Mesobaculum littorinae gen. nov., sp. nov., a novel bacterium isolated from a sea snail Littorina scabra.

Members within the family Rhodbacteraceae are morphologically and genetically highly diverse, and originate mostly from coastal marine environments. In this study, a novel species of this family, designated M0103T, was isolated from the surface of a sea snail Littorina scabra. Strain M0103T is Gram-stain-negative, halophilic, non-motile and non-Bacteriochlorophyll a-producing bacterium. Several phenotypic characteristics of the isolate were similar to other species within this family, such as the sole respiratory quinone Q-10 and major fatty acid components C18 : 1 ω7c, C18 : 0 and C16 : 0. Strain M0103T contains a diphosphatidylglycerol, a phosphatidylglycerol, a phosphatidylcholine, a phosphatidy ethanolamine, a phosphatidylinositol, five unidentified phospholipids and four unidentified polar lipids. Based on the 16S rRNA gene sequence analysis, this isolate showed the closest phylogenetic relationship with 'Palleronia pontilimi' GH1-23T (95.1 %). Values of average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) of genome sequences were of 70.1-76.4 % and 18.3-20.9 % between the isolate and 24 closely related type strains. Analysis the 4.0 Mb genome of strain M0103T revealed several putative genes associated with cellular stress resistance, which may play protective roles for the isolate in the adaptation to a marine environment. Phylogenetic, phenotypic and chemotaxonomic analyses suggested that strain M0103T represents a novel genus and novel species of the family Rhodobacteraceae, for which the name Mesobaculum littorinae gen. nov., sp. nov. is proposed. The type strain is M0103T (=MCCC 1K03619T=KCTC 62358T).

Hoyosella lacisalsi sp. nov., a halotolerant actinobacterium isolated from the Lake Gudzhirganskoe.

A Gram-stain-positive, aerobic, non-motile, non-spore-forming and coccus-shaped strain, designated strain G463T, was isolated from the rhizosphere soil of Salicornia europaea L. collected from Lake Gudzhirganskoe in Siberia. Based on 16S rRNA gene phylogeny, strain G463T belonged to the genus Hoyosella, with the highest 16S rRNA gene sequence similarity to Hoyosella altamirensis DSM 45258T (96.1%). The major fatty acids were C17:1 ω8c, C16:0, C15 : 0 and C17:0. The strain contained meso-diaminopimelic acid as the cell-wall diagnostic diamino acid and arabinose, galactose and ribose as the whole-cell sugars. MK-8 and MK-7 were the predominant menaquinones. The polar lipid profile comprised diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, one unidentified phosphoglycolipid, two unidentified glycolipids and several unidentified lipids. Acetyl was the muramyl residue. Mycolic acids (C28-C34) were present. The G+C content of the genomic DNA was 68.3 mol%. Based on its phylogenetic, phenotypic and chemotaxonomic features, strain G463T was considered to represent a novel species of the genus Hoyosella, for which the name Hoyosella lacisalsi sp. nov. is proposed. The type strain is G463T (=JCM 33650T=CGMCC 1.17230T).

Phycicoccus flavus sp. nov., a novel endophytic actinobacterium isolated from branch of Kandelia candel.

A Gram-stain-positive, aerobic, non-motile, non-endospore-forming and rod-shaped actinobacterium, designated strain CMS6Z-2T, was isolated from a surface-sterilized branch of Kandelia candel collected from the Maowei Sea, Guangxi Zhuang Autonomous Region, PR China. Strain CMS6Z-2T grew at 10-37 °C (optimum, 37 °C), pH 6.0-9.0 (optimum, pH 7.0-8.0) and in the presence of 0-10.0 % (w/v) NaCl (optimum, 0-1.0 %). Strain CMS6Z-2T possessed meso-diaminopimelic acid as the diamino acid of the peptidoglycan and MK-8 (H4) as the predominant menaquinone. The major fatty acids were iso-C15 : 0, C16 : 0 and C18 : 1 ω9c. The polar lipids comprised diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and two unknown phospholipids. The G+C content of the genomic DNA was 74.1 mol%. Comparative analysis of 16S rRNA genes showed that strain CMS6Z-2T should be assigned to the genus Phycicoccus and its closest relative was Phycicoccus endophyticus IP6SC6T with 98.3 % similarity. Phylogenetic analyses based on 16S rRNA gene sequence and phylogenomic analysis based on core proteomes alignment revealed that strain CMS6Z-2T belonged to the genus Phycicoccus and formed a robust cluster with Phycicoccus endophyticus IP6SC6T within the genus Phycicoccus. The average nucleotide identity value and estimated digital DNA-DNA hybridization value between strain CMS6Z-2T and the type strain of Phycicoccus endophyticus were 81.5 and 23.9 %, respectively. On the basis of phylogenetic, phenotypic and chemotaxonomic characteristics, strain CMS6Z-2T represents a novel species of the genus Phycicoccus, for which the name Phycicoccus flavus sp. nov. is proposed. The type strain is CMS6Z-2T (=KCTC 49240T=CGMCC4.7549T).

Schumannella soli sp. nov., a novel actinomycete isolated from mangrove soil by in situ cultivation.

A novel actinobacterial strain, designated 10F1D-1T, was isolated from soil sample collected from Futian mangrove nature reserve, China using of the in situ cultivation technique. Preliminary analysis based on the 16S rRNA gene sequence revealed that strain 10F1D-1T was the member of genus Schumannella with sharing highest sequence similarity (99.7%) to Schumannella luteola DSM 23141T. Phylogenetic analyses based on 16S rRNA gene sequences and core proteome consistently exhibited that strain 10F1D-1T formed a monophyletic clade with Schumannella luteola DSM 23141T. Comparative genomic analyses clearly separated strain 10F1D-1T from the only species of the genus Schumannella based on average nucleotide identity (ANI), average amino acid identity (AAI) and digital DNA-DNA hybridization (dDDH) values below the thresholds for species delineation. The genome of strain 10F1D-1T contains the biosynthetic gene clusters for osmoprotectants to adapt to the salt environment of mangrove. Strain 10F1D-1T also contains the biosynthetic gene clusters for bioactive compounds as secondary metabolites. On the basis of the polyphasic analysis, strain 10F1D-1T is considered to represent a novel species of the genus Schumannella, for which the name Schumannella soli sp. nov. (type strain 10F1D-1T = CGMCC1.16699T = JCM 33146T) is proposed.

Metabolomics Tools Assisting Classic Screening Methods in Discovering New Antibiotics from Mangrove Actinomycetia in Leizhou Peninsula.

Mangrove actinomycetia are considered one of the promising sources for discovering novel biologically active compounds. Traditional bioactivity- and/or taxonomy-based methods are inefficient and usually result in the re-discovery of known metabolites. Thus, improving selection efficiency among strain candidates is of interest especially in the early stage of the antibiotic discovery program. In this study, an integrated strategy of combining phylogenetic data and bioactivity tests with a metabolomics-based dereplication approach was applied to fast track the selection process. A total of 521 actinomycetial strains affiliated to 40 genera in 23 families were isolated from 13 different mangrove soil samples by the culture-dependent method. A total of 179 strains affiliated to 40 different genera with a unique colony morphology were selected to evaluate antibacterial activity against 12 indicator bacteria. Of the 179 tested isolates, 47 showed activities against at least one of the tested pathogens. Analysis of 23 out of 47 active isolates using UPLC-HRMS-PCA revealed six outliers. Further analysis using the OPLS-DA model identified five compounds from two outliers contributing to the bioactivity against drug-sensitive A. baumannii. Molecular networking was used to determine the relationship of significant metabolites in six outliers and to find their potentially new congeners. Finally, two Streptomyces strains (M22, H37) producing potentially new compounds were rapidly prioritized on the basis of their distinct chemistry profiles, dereplication results, and antibacterial activities, as well as taxonomical information. Two new trioxacarcins with keto-reduced trioxacarcinose B, gutingimycin B (16) and trioxacarcin G (20), together with known gutingimycin (12), were isolated from the scale-up fermentation broth of Streptomyces sp. M22. Our study demonstrated that metabolomics tools could greatly assist classic antibiotic discovery methods in strain prioritization to improve efficiency in discovering novel antibiotics from those highly productive and rich diversity ecosystems.

Beilunmycin, a new virginiamycins antibiotic from mangrove-derived Streptomyces sp. 2BBP-J2 and the antibacterial activity by inhibiting protein translation.

One new virginiamycin derivative, 'beilunmycin' (1), and three known virginiamycin antibiotics, 16-hydroxy-virginiamycin M1 (2), virginiamycin M2 (3), and virginiamycin M1 (4), were isolated from the culture of a mangrove-derived endophytic Streptomyces sp. 2BBP-J2. The structures were characterized on the basis of their spectroscopic data, and the absolute configuration of 1 was established by ECD calculations. Compounds 1-4 exhibited antibacterial activities against Gram-positive bacteria, with MIC values in the range of 0.5-16 µg/ml. All the compounds demonstrated strong protein translation-stalling activity, with minimal concentrations detected with pDualrep2 in the range of 1.9-5.9 nmol.

Nocardioides vastitatis sp. nov., isolated from Taklamakan desert soil.

A Gram-stain-positive, aerobic, non-motile, rod-shaped actinobacterium, designated strain 21Sc5-5T, was isolated from a soil sample collected in the Taklamakan desert in Xinjiang Uygur Autonomous Region, PR China and investigated by using a polyphasic approach. Strain 21Sc5-5T grew at 10-37 °C (optimum, 28-30 °C), pH 6.0-9.0 (optimum, pH 7.0) and in the presence of 0-3 % (w/v) NaCl (optimum, 0 %). Phylogenetic analysis based on 16S rRNA gene sequences suggested that strain 21Sc5-5T formed a distinct lineage within the genus Nocardioides and had the highest similarity to Nocardioides albidus THG-S11.7T (97.30 %), followed by Nocardioides kongjuensis A2-4T (97.22 %), Nocardioides nitrophenolicus NSP 41T (97.15 %) and Nocardioides caeni MN8T (97.15 %). The results of chemotaxonomic analyses showed that the isolate possessed ll-diaminopimelic acid as the diagnostic diamino acid of the peptidoglycan and MK-8(H4) as the predominant menaquinone. The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, an unidentified phospholipid and three unidentified lipids. The major fatty acids were iso-C16 : 0 and 10-methyl C18 : 0. The genome length of strain 21Sc5-5T was 4.67 Mb containing 372 contigs and with a DNA G+C content of 70.4 mol%. On the basis of data from phylogenetic, phenotypic and chemotaxonomic analyses, strain 21Sc5-5T represents a novel species of the genus Nocardioides, for which the name Nocardioides vastitatis sp. nov. is proposed. The type strain is 21Sc5-5T (=JCM 33365T=CGMCC 4.7608T).

Glycomyces buryatensis sp. nov., an actinobacterium isolated from steppe soil.

A novel actinobacterial strain, designated 18T, was isolated from a steppe soil sample collected in Buryatia, Russia and subjected to polyphasic taxonomic characterization. The strain was aerobic and Gram-stain-positive. The 16S rRNA gene sequence of strain 18T exhibited highest similarity to Glycomyces paridis CPCC 204357T (97.2 %). Results of phylogenetic analysis showed that strain 18T formed a distinct branch clearly affiliated to the genus Glycomyces. Whole-cell hydrolysates of the isolate contained meso-diaminopimelic acid as the cell-wall diamino acid. The whole-cell sugar profile was found to contain galactose, glucose, ribose and xylose. MK-10(H4) and MK-11(H4) were the predominant menaquinones. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, five unidentified phospholipids and four unidentified polar lipids. The major fatty acids identified were anteiso-C15 : 0 and iso-C15 : 0. The G+C content of the genomic DNA of strain 18T was 68.0 mol% (draft genome sequence). Based on its phylogenetic, phenotypic and chemotaxonomic features, strain 18T was considered to represent a novel species of the genus Glycomyces, for which the name Glycomyces buryatensis sp. nov. is proposed. The type strain of Glycomyces buryatensis is 18T (=JCM 33362T=CGMCC 4.7610T).

Desertihabitans brevis sp. nov., an actinobacterium isolated from sand of the Taklamakan desert, and emended description of the genus Desertihabitans.

A novel actinobacterium, designated strain 16Sb5-5T, was isolated from a sand sample collected in the Taklamakan desert in Xinjiang Uygur Autonomous Region, China. The strain was examined by a polyphasic approach to clarify its taxonomic position. Cells of the isolate were Gram-staining-positive, aerobic, non-motile and short-rod shaped. Strain 16Sb5-5T grew optimally at 37 °C, pH 7.0 and with 0‒2 % (w/v) NaCl. The cell-wall peptidoglycan was of the A3γ type and contained alanine, glycine, glutamic acid and ll-diaminopimelic acid (ll-DAP). Ribose, arabinose and glucose were detected in the whole-cell hydrolysates. The predominant menaquinone was MK-9(H4). The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, an unidentified phospholipid, three unidentified glycolipids and three unidentified lipids. The major whole-cell fatty acids were anteiso-C15 : 0 and iso-C15 : 0. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 16Sb5-5T was closely related to Desertihabitans aurantiacus CPCC 204711T (99.8 % similarity) and formed a robust clade with D. aurantiacus in the phylogenetic trees. In silico genomic comparisons showed that strain 16Sb5-5T exhibited ANI values of 94.8-94.9 % and GGDC value of 59.5 % to D. aurantiacus CPCC 204711T. The genomic G+C content was 73.3 mol%. On the basis of phylogenetic, phenotypic and chemotaxonomic analyses, strain 16Sb5-5T could be distinguishable from its closest phylogenetic relative and represents a novel species of the genus Desertihabitans, for which the name Desertihabitans brevis sp. nov. is proposed. The type strain is 16Sb5-5T (=KCTC 49116T=CGMCC 1.16553T). The description of the genus Desertihabitans has also been emended.

Planctomonas psychrotolerans sp. nov., isolated from rhizosphere soil of Suaeda salsa.

A psychrotolerant actinobacterium, designated strain J5903T, was isolated from an alkaline soil sample from the rhizosphere of Suaeda salsa collected in desertification land surrounding Jiuliancheng Nur in Hebei Province, PR China. Cells of the isolate were Gram-stain-positive, aerobic, non-motile and non-spore-forming cocci. Strain J5903T grew optimally at 20‒25 °C, at pH 7.0‒7.5 and with <1 % (w/v) NaCl. The cell-wall peptidoglycan type was B2γ with d-2,4-diaminobutyric acid and l-2,4-diaminobutyric acid as diagnostic amino acids. The muramyl residue was acetyl type. The menaquinones were MK-11, MK-12, MK-10 and MK-13. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and one unidentified glycolipid. The major whole-cell fatty acids were anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0. The genomic DNA G+C content was 69.1 mol%. It shared the highest average nucleotide identity and digital DNA-DNA hybridization values with Planctomonas deserti 13S1-3T. Phylogenies based on genome sequence showed that strain J5903T and P. deserti 13S1-3T formed a robust cluster with high bootstrap support. Strain J5903T shared typical chemotaxonomic characteristics with P. deserti 13S1-3T. Combining the polyphasic taxonomic evidence, strain J5903T represents a novel species of the genus Planctomonas, for which the name Planctomonas psychrotolerans sp. nov. is proposed. The type strain is J5903T (=DSM 101894T=CGMCC 1.15523T).

Arthrobacter mobilis sp. nov., a novel actinobacterium isolated from Cholistan desert soil.

A Gram-stain-positive, aerobic, catalase-positive, oxidase-negative, non-mycelium-forming, motile, rod-shaped with one polar flagellum actinobacterium, designated E918T, was isolated from a desert soil collected in Cholistan desert, Pakistan. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain E918T belonged to the genus Arthrobacter and was most closely related to Arthrobacter deserti CGMCC 1.15091T (97.2 % similarity). The peptidoglycan was of the A3α type and the whole-cell sugar profile was found to contain galactose. The major menaquinone was MK-9(H2). The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two unidentified glycolipids. The major fatty acids identified were anteiso-C15 : 0 and anteiso-C17 : 0. The G+C content of the genomic DNA was 68.69 mol%. The digital DNA-DNA hybridization and average nucleotide identity values between strain E918T and A. deserti CGMCC 1.15091T were 28.0 and 83.4%, respectively. On the basis of its phylogenetic, phenotypic and chemotaxonomic features, strain E918T was considered to represent a novel species of the genus Arthrobacter, for which the name Arthrobacter mobilis sp. nov. is proposed. The type strain of Arthrobacter mobilis is E918T (=JCM 33392T=CGMCC 1.16978T).

Auraticoccus cholistanensis sp. nov., an actinomycete isolated from soil of the Cholistan Desert, and emended description of the genus Auraticoccus.

A Gram-stain-positive, aerobic, non-motile and non-spore-forming actinobacterium, designated as F435T, was isolated from soil sample collected from the Cholistan Desert, Pakistan. The taxonomic position of the strain was established by using a polyphasic taxonomic approach. The cells were coccoid-shaped and found in single or arrangement of pairs. The novel strain grew at 15‒37 °C (optimum, 25‒30 °C), pH 7‒11 (optimum, pH 7-8) and in the presence of 0‒8% (w/v) NaCl (optimum, 0 %). Results of blast analysis based on 16S rRNA gene sequences showed that Auraticoccus monumenti MON 2.2T was its closest relative with 97.4 % similarity followed by Desertihabitans aurantiacus CPCC 204711T (95.2 %). In phylogenetic trees, strain F435T formed a robust cluster with the only member of the genus Auraticoccus. The peptidoglycan isomer present in the cell wall was ll-diaminopimelic acid. The major fatty acid was determined to be anteiso-C15 : 0. Characteristic polar lipids of the strain were diphosphatidylglycerol, phosphatidylglycerol, phosphoglycolipids and glycolipids. The predominant menaquinone was MK-9(H4). The genomic G+C content was calculated as 73.5 mol%. The digital DNA-DNA hybridization (GGDC) and average nucleotide identity (ANI) values between strain F435T and A. monumenti MON 2.2T were 24.6 and 81.8 %, respectively. Based on the results of phenotypic, chemotaxonomic, phylogenetic and phylogenomic analyses, strain F435T represents a novel specie of the genus Auraticoccus, for which the name Auraticoccus cholistanensis sp. nov. is proposed. The type strain is F435T (=JCM 33648T=CGMCC 1.17443T). The description of the genus Auraticoccus has also been emended.

Phytoactinopolyspora mesophila sp. nov., isolated from a saline-alkaline soil.

A novel moderately halophilic, filamentous actinobacterium, designated as XMNu-373T, was isolated from a saline-alkaline soil sample collected from the Mongolia Plateau, Dongwu County, Inner Mongolia Autonomous Region, PR China. The isolate grew optimally at 28‒37 °C, pH 7.0‒8.0 and with 2-5 % (w/v) NaCl. The substrate mycelia fragmented into rod-like elements, and the white aerial mycelia formed spore chains at maturity. The predominant menaquinone was MK-9(H4). The polar lipids were diphosphatidylglycerol, three unidentified phosphoglycolipids, an unidentified aminophospholipid, two phosphatidylinositol mannosides, four unidentified phospholipids, phosphatidylglycerol and two unidentified lipids. The major cellular fatty acids were iso-C16 : 0, anteiso-C17 : 0 and anteiso-C15 : 0. The genomic DNA G+C content was 66.2 mol%. It shared high 16S rRNA gene sequence similarities to Phytoactinopolyspora halotolerans YIM 96448T (96.1 %) and Phytoactinopolyspora endophytica EGI 60009T (96.0 %). Phylogenetic trees based on 16S rRNA gene sequences revealed that strain XMNu-373T resided in the clade of family Jiangellaceae, and it formed a monophyletic branch distinct from four other recognized type species in the subclade of the genus Phytoactinopolyspora. On the basis of polyphasic taxonomic evidence, strain XMNu-373T represents a novel species of the genus Phytoactinopolyspora, for which the name Phytoactinopolyspora mesophila sp. nov. is proposed. The type strain is XMNu-373T (=JCM 33740T=CGMCC 4.7654T).

Hetiamacin E and F, New Amicoumacin Antibiotics from Bacillus subtilis PJS Using MS/MS-Based Molecular Networking.

To combat escalating levels of antibiotic resistance, novel strategies are developed to address the everlasting demand for new antibiotics. This study aimed at investigating amicoumacin antibiotics from the desert-derived Bacillus subtilis PJS by using the modern MS/MS-based molecular networking approach. Two new amicoumacins, namely hetiamacin E (1) and hetiamacin F (2), were finally isolated. The planar structures were determined by analysis of extensive NMR spectroscopic and HR-ESI-MS data, and the absolute configurations were concluded by analysis of the CD spectrum. Hetiamacin E (1) showed strong antibacterial activities against methicillin-sensitive and resistant Staphylococcus epidermidis at 2-4 µg/mL, and methicillin-sensitive and resistant Staphylococcus aureus at 8-16 µg/mL. Hetiamacin F (2) exhibited moderate antibacterial activities against Staphylococcus sp. at 32 µg/mL. Both compounds were inhibitors of protein biosynthesis demonstrated by a double fluorescent protein reporter system.

Kocuria soli sp. nov., an actinobacterium isolated from soil.

A Gram-stain-positive, aerobic, coccoid-shaped, non-spore-forming actinobacterial strain, designated M5W7-7T, was isolated from a hot spring soil sample collected from Anshan, Liaoning province, PR China. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain M5W7-7T clustered closely with species of the genus Kocuria, and showed the highest sequence similarity of 97.1 % to Kocuria subflava YIM 13062T. Strain M5W7-7T grew at 10-37 °C (optimum, 37 °C), pH6.0-11.0 (pH 6.0-7.0) and in the presence of 0-7 % (w/v) NaCl (0 %). Substrate mycelia and aerial mycelia were not formed, and diffusible pigments were not observed on any media tested. Strain M5W7-7T contained MK-6(H2) and MK-7(H2) as the dominant menaquinones. The polar lipid profile of strain M5W7-7T contained diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids, an unidentified phospholipid and an unidentified lipid. The predominant whole-cell sugars were galactose and glucose. The predominant fatty acid was anteiso-C15 : 0. The DNA G+C content of strain M5W7-7T was 67.0 mol%. On the basis of phylogenetic relationships, phenotypic characterization and chemotaxonomic analyses, strain M5W7-7T represents a novel species of the genus Kocuria, for which the name Kocuriasoli sp. nov. is proposed. The type strain is M5W7-7T (=KCTC 49195T =CGMCC 1.13744T).

Nakamurella deserti sp. nov., isolated from rhizosphere soil of Reaumuria in the Taklamakan desert.

A Gram-stain-positive, aerobic, non-motile, non-spore-forming, coccus-shaped actinobacterium, designated strain 12Sc4-1T, was isolated from a soil sample collected in the Taklamakan desert in Xinjiang Uygur Autonomous Region, China. Strain 12Sc4-1T grew at 8‒35 °C (optimum, 28‒30 °C), pH 6.0‒9.0 (optimum, pH 7.0) and in the presence of 0‒3 % (w/v) NaCl (optimum, 0 %). Phylogenetic analysis based on 16S rRNA gene sequence suggested that strain 12Sc4-1T belonged to the genus Nakamurella and shared the highest 16S rRNA gene sequence similarity to Nakamurella silvestris S20-107T (96.94 %). Strain 12Sc4-1T showed <96.0 % 16S rRNA gene sequence similarities to all other recognized members of the genus Nakamurella. Chemotaxonomic analyses showed that the isolate possessed meso-diaminopimelic acid as the diagnostic diamino acid of the peptidoglycan, glucose, mannose and galactose as whole-cell sugars, and MK-8(H4) as the predominant menaquinone. The polar lipids comprised diphosphatidylglycerol, phosphatidylethanolamine, an unidentified aminophospholipid, phosphatidylinositol, an unidentified phospholipid, an unidentified phosphoglycolipid and an unidentified glycolipid. The major fatty acids were C16 : 0 and anteiso-C15 : 0. The DNA G+C content was 72.1 mol% (draft genome sequence). On the basis of phylogenetic, phenotypic and chemotaxonomic analyses, strain 12Sc4-1T represents a novel species of the genus Nakamurella, for which the name Nakamurelladeserti sp. nov. is proposed. The type strain is 12Sc4-1T (=KCTC 49114T=CGMCC 1.16555T).

Planctomonas deserti gen. nov., sp. nov., a new member of the family Microbacteriaceae isolated from soil of the Taklamakan desert.

A Gram-staining-positive, aerobic, irregular coccoid- to ovoid-shaped, non-spore-forming and motile bacterium, designated strain 13S1-3T, was isolated from a soil sample from the rhizosphere of Tamarix collected in the Taklamakan desert in Xinjiang Uygur Autonomous Region, PR China. The strain was examined by a polyphasic approach to clarify its taxonomic position. Strain 13S1-3T grew optimally at 28-30 °C, pH 7.0 and with 0-1 % (w/v) NaCl. The cell-wall peptidoglycan was of the B2γ type and contained d-alanine, d-glutamic acid, glycine, d-2,4-diaminobutyric acid and l-2,4-diaminobutyric acid. Ribose, xylose, glucose and galactose were detected as cell-wall sugars. The acyl type of the muramic acid was acetyl. The predominant menaquinones were MK-12, MK-11, MK-13 and MK-10. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids and one unidentified phospholipid. The major whole-cell fatty acids were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0. The DNA G+C content was 70.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that 13S1-3T represented a member of the family Microbacteriaceae and showed the highest level of 16S rRNA gene sequence similarity with Frondihabitans australicus E1HC-02T (97.11 %). Phylogenetic trees revealed that 13S1-3T formed a distinct lineage with respect to closely related genera within the family Microbacteriaceae. On the basis of the results of phylogenetic, phenotypic and chemotaxonomic analyses, 13S1-3T is distinguishable from phylogenetically related genera in the family Microbacteriaceae, and represents a novel species of a new genus, for which the name Planctomonas deserti gen. nov., sp. nov. is proposed. The type strain is 13S1-3T (=KCTC 49115T=CGMCC 1.16554T).