Tandem LC-MS Identification of Antitubercular Compounds in Zones of Growth Inhibition Produced by South African Filamentous Actinobacteria

Novel antitubercular compounds are urgently needed to combat drug-resistant Mycobacterium tuberculosis (Mtb). Filamentous actinobacteria have historically been an excellent source of antitubercular drugs. Despite this, drug discovery from these microorganisms has fallen out of favour due to the continual rediscovery of known compounds. To increase the chance of discovering novel antibiotics, biodiverse and rare strains should be prioritised. Subsequently, active samples need to be dereplicated as early as possible to focus efforts on truly novel compounds. In this study, 42 South African filamentous actinobacteria were screened for antimycobacterial activity using the agar overlay method against the Mtb indicator Mycolicibacterium aurum under six different nutrient growth conditions. Known compounds were subsequently identified through extraction and high-resolution mass spectrometric analysis of the zones of growth inhibition produced by active strains. This allowed the dereplication of 15 hits from six strains that were found to be producing puromycin, actinomycin D and valinomycin. The remaining active strains were grown in liquid cultures, extracted and submitted for screening against Mtb in vitro. Actinomadura napierensis B60^T was the most active sample and was selected for bioassay-guided purification. This resulted in the identification of tetromadurin, a known compound, but which we show for the first time to have potent antitubercular activity, with the MIC₉₀s within the range of 73.7-151.6 nM against M. tuberculosis H37Rv^Tin vitro under different test conditions. This shows that South African actinobacteria are a good source of novel antitubercular compounds and warrant further screening. It is also revealed that active hits can be dereplicated by HPLC-MS/MS analysis of the zones of growth inhibition produced by the agar overlay technique.

Discovery of Novel Cyclic Ethers with Synergistic Antiplasmodial Activity in Combination with Valinomycin

With drug resistance threatening our first line antimalarial treatments, novel chemotherapeutics need to be developed. Ionophores have garnered interest as novel antimalarials due to their theorized ability to target unique systems found in the Plasmodium-infected erythrocyte. In this study, during the bioassay-guided fractionation of the crude extract of Streptomyces strain PR3, a group of cyclodepsipeptides, including valinomycin, and a novel class of cyclic ethers were identified and elucidated. Further study revealed that the ethers were cyclic polypropylene glycol (cPPG) oligomers that had leached into the bacterial culture from an extraction resin. Molecular dynamics analysis suggests that these ethers are able to bind cations such as K⁺, NH₄⁺ and Na⁺. Combination studies using the fixed ratio isobologram method revealed that the cPPGs synergistically improved the antiplasmodial activity of valinomycin and reduced its cytotoxicity in vitro. The IC₅₀ of valinomycin against P. falciparum NF54 improved by 4-5-fold when valinomycin was combined with the cPPGs. Precisely, it was improved from 3.75 ± 0.77 ng/mL to 0.90 ± 0.2 ng/mL and 0.75 ± 0.08 ng/mL when dosed in the fixed ratios of 3:2 and 2:3 of valinomycin to cPPGs, respectively. Each fixed ratio combination displayed cytotoxicity (IC₅₀) against the Chinese Hamster Ovary cell line of 57-65 µg/mL, which was lower than that of valinomycin (12.4 µg/mL). These results indicate that combinations with these novel ethers may be useful in repurposing valinomycin into a suitable and effective antimalarial.

Phylogenomic revision of the family Streptosporangiaceae, reclassification of Desertactinospora gelatinilytica as Spongiactinospora gelatinilytica comb. nov. and a taxonomic home for the genus Sinosporangium in the family Streptosporangiaceae

In recent years, the results of genome-based phylogenetic analyses have contributed to microbial systematics by increasing the availability of sequenced microbial genomes. Therefore, phylogenomic analysis within large taxa in the phylum Actinobacteria has appeared as a useful tool to clarify the taxonomic positions of ambiguous groups. In this study, we provide a revision of the actinobacterial family Streptosporangiaceae using a large collection of genome data and phylogenomics approaches. The phylogenomic analyses included the publicly available genome data of the members of the family Streptosporangiaceae and the state-of-the-art tools are used to infer the taxonomic affiliation of these species within the family. By comparing genome-based and 16S rRNA gene-based trees, as well as pairwise genome comparisons, the recently described genera Spongiactinospora and Desertactinospora are combined in the genus Spongiactinospora. In conclusion, a comprehensive phylogenomic revision of the family Streptosporangiaceae is proposed.

Bailinhaonella thermotolerans gen. nov., sp. nov., a new member of the order Streptosporangiales

A Gram-positive, aerobic, non-motile actinobacterium, designated YIM 75507^T, that was isolated from a soil sample collected from a dry-hot valley, was subjected to a polyphasic taxonomic study. The isolate formed branched hyphae and no fragmentation was found. Clustered spore chains were borne from aerial mycelium. The cell-wall peptidoglycan contained glutamic acid, alanine and meso-diaminopimelic acid. Whole-cell sugars were galactose, mannose, glucosamine, glucose and ribose. The major menaquinones were MK-9(H6), MK-9(H8) and MK-10(H6). The polar phospholipids contained phosphatidylmethylethanolamine, phosphatidylethanolamine and ninhydrin-positive phosphoglycolipid. Major fatty acids were iso-C16 : 0 and 10-methyl-C17 : 0. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain YIM 75507^T formed a stable and distinct lineage clustered with the genus Sinosporangium in the family Streptosporangiaceae. The draft genome sequence of strain YIM 75507^T exhibited low average nucleotide identity to the closest related strain, Sinosporangium album CPCC 201354^T (83.97 %), well below the 95-96 % species circumscription threshold. The G+C content of the genomic DNA was 73.8 mol%. On the basis of morphological, chemotaxonomic and phylogenetic evidence, strain YIM 75507^T is assigned to a novel species of a new genus, for which the name Bailinhaonella thermotolerans gen. nov., sp. nov. is proposed. The type strain of Bailinhaonella thermotolerans is YIM 75507^T (=KCTC 49229^T=CGMCC 4.7547^T).

Spongiactinospora rosea gen. nov., sp. nov., a new member of the family Streptosporangiaceae

A novel aerobic, spore-forming, marine actinomycete, designated strain LHW63015^T, was isolated from a Craniella marine sponge collected in the South China Sea. The strain formed extensively branched substrate and aerial mycelia which carried long and crooked spore chains composed of ridged spores and spherical pseudosporangia. Strain LHW63015^T contained meso-diaminopimelic acid as the diagnostic diamino acid. Glucose, ribose, mannose, galactose and madurose occured in whole-cell hydrolysates. The predominant polar lipids were hydroxyl-phosphatidylethanolamine, phosphoglycolipid and ninhydrin-positive phosphoglycolipid. MK-10(H4) and MK-10(H6) were the predominant menaquinones. The major fatty acids were 10-methyl C17 : 0 and C17 : 1ω8c. The G+C content of the genomic DNA was 70.8 mol%. In phylogenetic analysis based on 16S rRNA gene sequences, strain LHW63015^T fell within the family Streptosporangiaceae and formed a distinct monophyletic lineage adjacent to the genus Sphaerisporangium, and shared the highest 16S rRNA gene sequence similarity of 96.2 % with Sphaerisporangium album YIM 48782^T. On the basis of the polyphasic evidence, a novel genus and species of the family Streptosporangiaceae, for which the name Spongiactinospora rosea gen. nov., sp. nov., is proposed, with the type strain LHW63015^T (=DSM 106635^T=CCTCC AA 2018019^T).

Sphaerisporangium rhizosphaerae sp. nov., an actinomycete isolated from the rhizosphere soil of a rubber tree (Hevea brasiliensis Muell. Arg)

A novel actinomycete, designated strain NEAU-mq3^T, was isolated from the rhizosphere soil of a rubber tree (Hevea brasiliensis Muell. Arg) collected from Xianglu Mountain in Heilongjiang Province, north-east China, and characterized by using a polyphasic approach. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that the organism should be assigned to the genus Sphaerisporangium and that it forms a monophyletic clade with its closest relatives 'Sphaerisporangium dianthi' NEAU-CY18^T (99.2 % 16S rRNA gene sequence similarity) and Sphaerisporangium cinnabarinum JCM 3291^T (98.8 %). Morphological and chemotaxonomic properties of strain NEAU-mq3^T were also consistent with the description of the genus Sphaerisporangium. The whole-cell sugars were madurose, mannose, ribose and glucose. The menaquinones were MK-9(H2), MK-9(H4), MK-9(H0) and MK-9(H6). The diagnostic diamino acid of the peptidoglycan was meso-diaminopimelic acid. The phospholipid profile consisted of diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, phosphatidylinositol mannoside, an unidentified polar lipid and an unidentified phospholipid. The major fatty acids were identified as iso-C16 : 0, 10-methyl C17 : 0, C16 : 1ω7c and C17 : 1ω7c. DNA-DNA hybridization experiments and phenotypic tests were carried out between strain NEAU-mq3^T and its most closely related strains, which further clarified their relatedness and demonstrated that NEAU-mq3^T could be distinguished from these strains. Therefore, it is concluded that strain NEAU-mq3^T represents a novel species of the genus Sphaerisporangium, for which the name Sphaerisporangium rhizosphaerae sp. nov. is proposed. The type strain is NEAU-mq3^T (=CGMCC 4.7429^T=JCM 32389^T).

High-Quality Draft Genome Sequence of Sphaerisporangium cinnabarinum ATCC 31213

A high-quality draft genome sequence of Sphaerisporangium cinnabarinum ATCC 31213 is presented here. This bacterium produces several important bioactive compounds and may also produce functional amyloids. This is the first sequenced genome from the genus Sphaerisporangium , and it will be essential in determining the nature of the potential amyloid protein.

Planomonospora corallina sp. nov., isolated from soil

A novel actinomycete strain, A-T 11038T, was isolated from bamboo rhizospheric soil collected in Thailand. Based on a polyphasic approach, the novel strain was characterized as a member of the genus Planomonospora, which developed cylindrical to clavate sporangia containing a single motile spore on aerial mycelium. The 16S rRNA gene sequence and phylogenetic analysis indicated that strain A-T 11038T was closely related to Planomonospora sphaerica JCM 9374T (98.82 %), P.lanomonospora parontospora subsp. parontospora NBRC 13880T and P.parontospora subsp. antibiotica JCM 3094T (98.54 %), Planomonospora alba JCM 9373T (98.41 %) and Planomonospora venezuelensis JCM 3167T (97.51 %). The DNA-DNA relatedness values that distinguished strain A-T 11038T from the most closely related species were below 45 %. The novel strain contained meso-diaminopimelic acid in cell-wall hydrolysates, and rhamnose, ribose, madurose and glucose in whole-cell hydrolysates. The predominant menaquinone was MK-9(H2). The diagnostic phospholipids were diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol mannosides, phosphatidylinositol and aminophosphoglycolipids. The predominant cellular fatty acids were unsaturated fatty acids C17 : 1 and C16 : 1 and saturated fatty acid C16 : 0. The G+C content of the genomic DNA was 73.5 mol%. Following the evidence obtained using a polyphasic approach, the novel strain is proposed as a representative of a novel species to be named Planomonospora corallina sp. nov. The type strain is A-T 11038T (=BCC 67829T=TBRC 4489T=NBRC 110609T).

Sphaerisporangium aureirubrum sp. nov., an actinomycete isolated from soil

A novel actinomycete, designated strain NEAU-GQTH1-3T, was isolated from muddy soil collected from a stream in Qitaihe, Heilongjiang Province, north-east China and characterized using a polyphasic approach. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that the organism should be assigned to the genus Sphaerisporangium and forms a stable clade with its closest relative Sphaerisporangium rubeum JCM 13067T (98.2 % 16S rRNA gene sequence similarity). Moreover, morphological and chemotaxonomic properties of strain NEAU-GQTH1-3T also confirmed the affiliation of the isolate to the genus Sphaerisporangium. The cell wall contained meso-diaminopimelic acid and the whole-cell sugars were glucose, galactose, madurose, mannose and ribose. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylinositol, two phosphatidylinositol mannosides, phosphoglycolipid, an unidentified phospholipid and an unidentified glycolipid. The major menaquinones were MK-9(H4), MK-9(H6) and MK-9(H2). The predominant cellular fatty acids were iso-C16 : 0 and 10-methyl C17 : 0. Mycolic acids were absent. The DNA G+C content was 70.4 mol%. However, the low level of DNA-DNA relatedness and some phenotypic characteristics allowed the isolate to be differentiated from its closest relative. Therefore, it is concluded that strain NEAU-GQTH1-3T represents a novel species of the genus Sphaerisporangium, for which the name Sphaerisporangium aureirubrum sp. nov. is proposed. The type strain is NEAU-GQTH1-3T ( = CGMCC 4.7199T = JCM 30346T).

Sphaerisporangium corydalis sp. nov., isolated from the root of Corydalis yanhusuo L

Two Gram-stain positive, aerobic actinomycete strains, designated NEAU-YHS12 and NEAU-YHS15(T), were isolated from the root of Corydalis yanhusuo L. collected from Wuchang, Heilongjiang Province, northeast China. Phylogenetic analysis of 16S rRNA gene sequences showed that the two strains are closely related to one another (99.8 % similarity), and had the closest relationship with Sphaerisporangium cinnabarinum JCM 3291(T) (98.7, 98.6 %), Sphaerisporangium flaviroseum YIM 48771(T) (98.6, 98.6 %), Sphaerisporangium melleum JCM 13064(T) (98.5, 98.4 %) and Sphaerisporangium dianthi NEAU-CY18(T) (98.4, 98.4 %). DNA-DNA hybridization value between strains NEAU-YHS12 and NEAU-YHS15(T) was 82 ± 1.4 %, and the values between the two strains and the closely related type strains were well below 70 %. The two strains also shared a number of phenotypic characteristics that were distinct from the closely related species. Both strains were observed to contain MK-9(H6), MK-9(H4) and MK-9(H2) as the detected menaquinones. The cell wall peptidoglycan was found to contain meso-diaminopimelic acid. The phospholipid profiles were found to contain diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside, phosphoglycolipid, and an unidentified phospholipid. The major fatty acids were identified as iso-C16:0, C17:1 ω7c, C18:0 and iso-C15:0. On the basis of the genetic and phenotypic properties, it is proposed that strains NEAU-YHS15(T) and NEAU-YHS12 be classified as representatives of a novel species of the genus Sphaerisporangium, for which the name Sphaerisporangium corydalis sp. nov is proposed. The type strain is NEAU-YHS15(T) (CGMCC 4.7148(T) = DSM46732(T)).

Sphaerisporangium dianthi sp. nov., an endophytic actinomycete isolated from a root of Dianthus chinensis L

A novel actinomycete, designated strain NEAU-CY18(T), was isolated from the root of a Chinese medicinal plant Dianthus chinensis L and subjected to a polyphasic taxonomic study. The novel strain was found to develop spherical sporangia with non-motile spores on aerial mycelium. The cell-wall peptidoglycan was found to contain meso-diaminopimelic acid. The whole-cell sugars were identified as madurose, mannose, ribose, galactose and glucose. The phospholipid profile was found to contain diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, hydroxy-phosphatidylmethylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides and an unidentified phospholipid. The predominant menaquinones were identified as MK-9(H4), MK-9(H2) and MK-9(H6). The major fatty acids were identified as C17:0 10-methyl, iso-C16:0 and C16:0. EzTaxon-e analysis of the 16S rRNA gene sequence indicated that the strain belongs to the genus Sphaerisporangium and was most closely related to Sphaerisporangium cinnabarinum JCM 3291(T) (98.9 %) and Sphaerisporangium melleum JCM 13064(T) (98.3 %). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain NEAU-CY18(T) forms a monophyletic clade with S. cinnabarinum JCM 3291(T), an association that was supported by a bootstrap value of 97 % in the neighbour-joining tree and also recovered with the maximum-likelihood algorithm. Comparisons of some phenotypic properties and low DNA-DNA relatedness values enabled the strain to be differentiated from S. cinnabarinum JCM 3291(T) and S. melleum JCM 13064(T). Therefore, it is concluded that strain NEAU-CY18(T) represents a novel Sphaerisporangium species, for which the name Sphaerisporangium dianthi sp. nov. is proposed. The type strain is NEAU-CY18(T) ( = CGMCC 4.7132(T) = DSM 46736(T)).

Gyrase subunit B amino acid signatures for the actinobacterial family Streptosporangiaceae

Higher order taxonomic assignments (family level and above) in the phylum Actinobacteria are currently based only on 16S-rRNA gene sequence analyses. Additional molecular markers need to be identified to increase the number of reference points for defining actinobacterial families and other higher taxa. Furthermore, since most novel actinobacterial taxa are defined at the level of species and genera, it is necessary to define molecular signatures at the genus level to enhance the robustness of genus descriptions. The current use of chemotaxonomic markers to define genera could be improved by the identification of genus-specific molecular signatures. In this study, GyrB amino acid sequences for members of the family Streptosporangiaceae were analysed for molecular signatures. Phylogenetic analyses showed that the gyrB gene tree supported the composition of the currently recognised genera in this family. The catalytically important amino acids were identified in the GyrB sequences, as were the GHKL superfamily motifs. Examination of GyrB protein sequence alignments revealed that there are genus-specific sequences for most of the multi-species genera and genus-defining amino acid insertions for the genera Herbidospora and Microbispora. Furthermore, there are GyrB signature amino acids which distinguish the family Streptosporangiaceae from the family Nocardiopsaceae.

Planobispora takensis sp. nov., isolated from soil

A novel Gram-stain-positive, filamentous bacterial strain (A-T 7458(T)) was isolated from soil collected from hill evergreen forest in Thailand. The strain developed cylindrical sporangia containing a longitudinal pair of motile spores, on short ramifications of aerial mycelia. From a taxonomic study using a polyphasic approach, strain A-T 7458(T) had typical characteristics of members of the genus Planobispora. 16S rRNA gene sequence analysis indicated that the isolate was closely related to Planobispora siamensis A-T 4600(T) (98.5 %), Planobispora rosea JCM 3166(T) (97.6 %) and Planobispora longispora NBRC 13918(T) (97.6 %). The DNA-DNA relatedness values, which differentiated the novel strain from the closest species, were significantly below 70 %. The cell-wall peptidoglycan contained meso-diaminopimelic acid. The whole-cell sugars contained ribose, madurose, mannose and glucose. The predominant menaquinone was MK-9(H2). The diagnostic phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylinositol, phosphatidylinositol-mannoside and aminophosphoglycolipid. The predominant cellular fatty acids were unsaturated C17 : 1 and C18 : 1, and saturated C16 : 0 and C17 : 0. Following an evaluation of phenotypic, chemotaxonomic and genotypic characteristics, the novel isolate is proposed to represent a novel species of the genus Planobispora, to be named Planobispora takensis sp. nov. The type strain is A-T 7458(T) ( = BCC 48396(T) = NBRC 109077(T)).

Sphaerisporangium rufum sp. nov., an endophytic actinomycete from roots of Oryza sativa L

An endophytic actinomycete, strain R10-82(T), isolated from surface-sterilized roots of rice (Oryza sativa L.) was studied using a polyphasic approach. Strain R10-82(T) produced branching substrate mycelia and developed spherical spore vesicles on aerial hyphae containing non-motile spores. The major cellular fatty acids were iso-C16 : 0, iso-C14 : 0 and 10-methyl C17 : 0. The predominant menaquinones were MK-9, MK-9(H2), MK-9(H4) and MK-9(H6). Rhamnose, ribose, madurose, mannose and glucose were detected in whole-cell hydrolysates. The diagnostic phospholipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol mannosides, hydroxylphosphatidylethanolamine and ninhydrin-positive phosphoglycolipids. These morphological and chemotaxonomic data were similar to those of the genus Sphaerisporangium. Analysis of the 16S rRNA gene sequence revealed that strain R10-82(T) was related most closely to Sphaerisporangium cinnabarinum JCM 3291(T) (98.3 % similarity). The DNA G+C content of strain R10-82(T) was 74 mol%. DNA-DNA relatedness data in combination with differences in the biochemical and physiological properties suggested that strain R10-82(T) should be classified as representing a novel species of the genus Sphaerisporangium, for which the name Sphaerisporangium rufum is proposed. The type strain is R10-82(T) ( = BCC 51287(T) = NBRC 109079(T)). An emended description of the genus Sphaerisporangium is also provided.

Planobispora siamensis sp. nov., isolated from soil

A novel actinomycete strain, A-T 4600(T), which developed cylindrical sporangia containing a longitudinal pair of motile spores forming singly or in bundles on short ramifications of the aerial mycelium, was isolated from soil collected from an evergreen forest in Thailand. The cell-wall peptidoglycan contained meso-diaminopimelic acid. The whole-cell sugars contained ribose, madurose, mannose and glucose. The predominant menaquinones were MK-9(H2). Mycolic acids were not detected. The diagnostic phospholipids were phosphatidylethanolamine, phosphatidylmethylethanolamine, phosphatidylinositol, phosphatidylglycerol, phosphatidylinositol mannoside, diphosphatidylglycerol and aminophosphoglycolipid. The predominant cellular fatty acids were unsaturated C17 : 1, C18 : 1, saturated C16 : 0, and C17 : 0. The G+C content of the DNA was 70.8 mol%. Phenotypic and chemotaxonomic analyses showed that the isolate had the typical characteristics of members of the genus Planobispora. Furthermore, 16S rRNA gene sequence analysis also indicated that this strain belonged to the genus Planobispora but as a putative novel species. DNA-DNA relatedness values that differentiate the isolate from previously described members of the genus Planobispora were significantly below 70 %. Following an evaluation of phenotypic, chemotaxonomic and genotypic studies, it is proposed that the isolate represents a novel species, Planobispora siamensis sp. nov.; the type strain is A-T 4600(T) ( = BCC 39469(T) = NBRC 107568(T)).

Microbispora thailandensis sp. nov., an actinomycete isolated from cave soil

The taxonomic position of actinomycete strain NN276(T), isolated from cave soil, was studied using the polyphasic taxonomic approach. A phylogenetic tree based on 16S ribosomal RNA (rRNA) gene sequences showed that the isolate formed a distinct evolutionary linage with the genus Microbispora, with M. mesophila JCM 3151(T) as its closest phylogenetic neighbor (97.9% similarity). The organism contained meso-diaminopimelic acid and the N-acetyl type of peptidoglycan. Madurose was detected in the whole-cell hydrolasate. The predominant menaquinones were MK-9(H(4)), MK-9(H(2)) and MK-9. Mycolic acids were not detected. Major phospholipids were diphosphatidylglycerol, hydroxy-phosphatidylethanolamine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannoside. The major cellular fatty acid was iso-C(16: 0) and G+C content 70 mol%. DNA-DNA hybridization demonstrated that the isolate was distinct from M. mesophila JCM 3151(T). On the basis of phenotypic and genotypic data, it is proposed that strain NN276(T) represents a novel species of the genus Microbispora, hence the name Microbispora thailandensis sp. nov. The type strain is strain NN276(T) (=BCC 41490(T)=NRRL B-24806(T)=NBRC 107569(T)).

Thermocatellispora tengchongensis gen. nov., sp. nov., a new member of the family Streptosporangiaceae

A novel Gram-positive, aerobic, spore-forming, thermophilic actinomycete, designated strain YIM 77521(T), was isolated from a sandy soil sample collected at Rehai National Park, Tengchong, Yunnan province, south-west China. The strain formed branched substrate mycelia and no fragmentation was found. Masses of short, straight or irregular chains of three to eight warty ornamented spores were borne from aerial mycelia. The strain contained meso-diaminopimelic acid in the cell wall and the whole-cell sugars contained mannose, galactose, glucose and ribose. The predominant menaquinones were MK-9(H(4)), MK-9(H(6)) and MK-9(H(8)). The diagnostic polar lipids were diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, hydroxyphosphatidylmonomethylethanolamine and N-acetylglucosamine-containing phospholipids. The major fatty acids were iso-C(16 : 0), C(17 : 0) 10-methyl and C(18 : 0). The DNA G+C content of strain YIM 77521(T) was 73.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain YIM 77521(T) fell within the radiation of the suborder Streptosporangineae and formed a distinct monophyletic lineage adjacent to the family Streptosporangiaceae with a high bootstrap value. On the basis of combined data from the phenotypic and phylogenetic analyses, strain YIM 77521(T) represents a novel genus and species within the family Streptosporangiaceae, for which the name Thermocatellispora tengchongensis gen. nov., sp. nov. is proposed. The type strain is YIM 77521(T) ( = DSM 45615(T)  = CCTCC AA 2011013(T)).

Taxonomic and ecological studies of actinomycetes from Vietnam: isolation and genus-level diversity

Actinomycetes were isolated from 109 soil and 93 leaf-litter samples collected at five sites in Vietnam between 2005 and 2008 using the rehydration-centrifugation (RC) method, sodium dodecyl sulfate-yeast extract dilution method, dry-heating method and oil-separation method in conjunction with humic acid-vitamin agar as an isolation medium. A total of 1882 strains were identified as Vietnamese (VN)-actinomycetes including 1080 (57%) streptomycetes (the genus Streptomyces isolates) and 802 (43%) non-streptomycetes. The 16S ribosomal RNA gene sequences of the VN-actinomycetes were analyzed using BLAST searches. The results showed that these isolates belonged to 53 genera distributed among 21 families. Approximately 90% of these strains were members of three families: Streptomycetaceae (1087 strains, 58%); Micromonosporaceae (516 strains, 27%); and Streptosporangiaceae (89 strains, 5%). Motile actinomycetes of the genera Actinoplanes, Kineosporia and Cryptosporangium, which have quite common morphological characteristics, were frequently isolated from leaf-litter samples using the RC method. It is possible that these three genera acquired common properties during a process of convergent evolution. By contrast, strains belonging to the suborder Streptosporangineae were exclusively isolated from soils. A comparison of the sampling sites revealed no significant difference in taxonomic diversity between these sites. Among the non-streptomycetes, 156 strains (19%) were considered as new taxa distributed into 21 genera belonging to 12 families. Interestingly, the isolation of actinomycetes from leaf-litter samples using the RC method proved to be the most efficient way to isolate new actinomycetes in Vietnam, especially the Micromonosporaceae species.

Sphaerisporangium siamense sp. nov., an actinomycete isolated from rubber-tree rhizospheric soil

A Gram-positive aerobic actinomycete, designated SR14.14(T), isolated from the rhizospheric soil of rubber tree was determined taxonomically using a polyphasic approach. The organism contained meso-diaminopimelic acid and the N-acetyl type of peptidoglycan. The predominant menaquinones were MK-9, MK-9(H₂) and MK-9(H₄). Madurose was detected in the whole-cell hydrolysates. Mycolic acids were not presented. Major phospholipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol mannoside. Major cellular fatty acid was iso-C(₁₆:₀) and the G+C content was 71.9 mol %. Phylogenetic analysis based on 16S rRNA gene sequence suggested that the isolate belongs to the genus Sphaerisporangium. The sequence similarity value between the strain SR14.14(T) and its closely related species, Sphaerisporangium album, was 97.8%. DNA-DNA hybridization values between them were well below 70%. Based on genotypic and phenotypic data, strain SR14.14(T) represents a novel species in the genus Sphaerisporangium, for which the name Sphaerisporangium siamense sp. nov. is proposed. The type strain is SR14.14(T) (=BCC 41491(T)=NRRL B-24805(T)=NBRC 107570(T)).

Sinosporangium album gen. nov., sp. nov., a new member of the suborder Streptosporangineae

A Gram-positive, aerobic, non-motile actinobacterium, designated strain 6014T, was isolated from a soil sample collected from Qinghai province, north-west China, and subjected to a polyphasic taxonomic study. The isolate formed elementary branching hyphae and abundant aerial mycelia with globose sporangia on ISP 4 and R2A media. Whole-cell hydrolysates of strain 6014T contained arabinose, galactose and ribose as diagnostic sugars and meso-diaminopimelic acid as the diagnostic diamino acid. The polar lipids consisted of phosphatidylmethylethanolamine, phosphatidylethanolamine, hydroxy-phosphatidylethanolamine, N-acetylglucosamine-containing phospholipids, two unknown phospholipids and an unknown glycolipid. The menaquinone system contained MK-9(H2) and MK-9(H4). The major fatty acids were C14 : 0, i-C15 : 0, C16 : 0 and 10-methyl-C16 : 1. The genomic DNA G+C content of the isolate was 69.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 6014T fell within the radius of the suborder Streptosporangineae, in which the strain formed a distinct lineage next to genera of the family Streptosporangiaceae. Based on data from this polyphasic study, strain 6014T can be readily distinguished from previously described organisms and represents a member of a novel species within a new genus in the suborder Streptosporangineae. The name Sinosporangium album gen. nov., sp. nov. is proposed with 6014T (=DSM 45181T =KCTC 19655T) as the type strain.

Sphaerisporangium krabiense sp. nov., isolated from soil

A Gram-staining-positive, filamentous bacterial strain, designated A-T 0308(T), was isolated from soil of a tropical mangrove forest in Thailand. Strain A-T 0308(T) developed spherical sporangia containing non-motile spores on aerial mycelium. The novel strain contained meso-diaminopimelic acid, N-acetyl-type peptidoglycan and madurose, mannose, ribose, galactose and glucose as whole-cell sugars. The predominant menaquinones were MK-9(H(4)) and MK-9(H(6)); a small amount of MK-9(H(2)) and MK-9 was also detected. Mycolic acids were not detected. The diagnostic phospholipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside and phosphoglycolipid. The predominant cellular fatty acids were iso-C(16:0) and 10-methylated C(17:0). The G+C content of the DNA was 72 mol%. Phenotypic and chemotaxonomic analyses showed that the novel isolate had characteristics typical of members of the genus Sphaerisporangium. 16S rRNA gene sequence analysis also indicated that the strain belongs to the genus Sphaerisporangium and that it represents a clade distinct from other members of the genus with sequence similarities ranging from 96.3 to 97.8% between the novel strain and its closest relatives. Based on the results of phenotypic, chemotaxonomic and phylogenetic studies, strain A-T 0308(T) (=BCC 21702(T) =NBRC 107571(T)) represents a novel species of the genus Sphaerisporangium, for which the name Sphaerisporangium krabiense sp. nov. is proposed.

Biosynthetic potential of phylogenetically unique endophytic actinomycetes from tropical plants

The culturable diversity of endophytic actinomycetes associated with tropical, native plants is essentially unexplored. In this study, 123 endophytic actinomycetes were isolated from tropical plants collected from several locations in Papua New Guinea and Mborokua Island, Solomon Islands. Isolates were found to be prevalent in roots but uncommon in leaves. Initially, isolates were dereplicated to the strain level by ribotyping. Subsequent characterization of 105 unique strains by 16S rRNA gene sequence analysis revealed that 17 different genera were represented, and rare genera, such as Sphaerisporangium and Planotetraspora, which have never been previously reported to be endophytic, were quite prevalent. Phylogenetic analyses grouped many of the strains into clades distinct from known genera within Thermomonosporaceae and Micromonosporaceae, indicating that they may be unique genera. Bioactivity testing and liquid chromatography-mass spectrometry (LC-MS) profiling of crude fermentation extracts were performed on 91 strains. About 60% of the extracts exhibited bioactivity or displayed LC-MS profiles with spectra indicative of secondary metabolites. The biosynthetic potential of 29 nonproductive strains was further investigated by the detection of putative polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) genes. Despite their lack of detectable secondary metabolite production in fermentation, most were positive for type I (66%) and type II (79%) PKS genes, and all were positive for NRPS genes. These results suggest that tropical plants from New Guinea and the adjacent archipelago are hosts to unique endophytic actinomycetes that possess significant biosynthetic potential.

Pseudosporangium ferrugineum gen. nov., sp. nov., a new member of the family Micromonosporaceae

An actinomycete strain 3-44-a(19)(T) was isolated from sandy soil collected in Bangladesh. The strain formed irregular pseudosporangia directly from aggregated spore chains above the rudimentary aerial mycelium. The pseudosporangia developed singly. Each pseudosporangium contained many small, non-motile, spherical, smooth-surfaced spores in chains. Strain 3-44-a(19)(T) contained meso- and 3-hydroxydiaminopimelic acid in the cell wall and MK-9(H(6)) as the major menaquinone and arabinose, galactose, glucose, mannose, ribose and xylose were present in the whole-cell hydrolysate. The diagnostic phospholipid was phosphatidylethanolamine and iso-C(15 : 0) (24.6 %), C(18 : 1)omega9c (15.5 %), C(16 : 0) (10.6 %), C(18 : 0) (9.4 %), iso-C(16 : 0) (8.6 %) and anteiso-C(15 : 0) (6.0 %) were detected as the major cellular fatty acids. The acyl type of the peptidoglycan was glycolyl and mycolic acids were not detected. The G+C content of the DNA was 73.6 mol%. The chemotaxonomic data indicated that the strain belonged to the family Micromonosporaceae. Phylogenetic analysis based on 16S rRNA gene sequence data also suggested that strain 3-44-a(19)(T) fell within the family Micromonosporaceae. On the basis of phylogenetic analysis and characteristic patterns of 16S rRNA gene signature nucleotides as well as morphological and chemotaxonomic data, this strain should be classified as a member of a new genus and species, Pseudosporangium ferrugineum gen. nov., sp. nov., in the family Micromonosporaceae. The type strain of Pseudosporangium ferrugineum is 3-44-a(19)(T) (=JCM 14710(T) =MTCC9007(T)).

List of new names and new combinations previously effectively, but not validly, published

The purpose of this announcement is to effect the valid publication of the followingeffectivelypublished new names and new combinations under the procedure described in theBacteriological Code(1990 Revision). Authors and other individuals wishing to have new names and/or combinations included in future lists should sendthree copies of the pertinent reprint or photocopies thereof, or an electronic copy of the published paper, to the IJSEM Editorial Officefor confirmation that all of the other requirements for valid publication have been met.It is also a requirement of IJSEM and the ICSP that authors of new species, new subspecies and new combinations provide evidence that types are deposited in two recognized culture collections in two different countries(i.e. documents certifying deposition and availability of type strains). It should be noted that the date of valid publication of these new names and combinations is the date of publication of this list, not the date of the original publication of the names and combinations. The authors of the new names and combinations are as given below, and these authors' names will be included in the author index of the present issue and in the volume author index. Inclusion of a name on these lists validates the publication of the name and thereby makes it available in bacteriological nomenclature. The inclusion of a name on this list is not to be construed as taxonomic acceptance of the taxon to which the name is applied. Indeed, some of these names may, in time, be shown to be synonyms, or the organisms may be transferred to another genus, thus necessitating the creation of a new combination.