Longispora albida gen. nov., sp. nov., a novel genus of the family Micromonosporaceae

Unravelling the genomic and environmental diversity of the ubiquitous Solirubrobacter

Solirubrobacter, though widespread in soils and rhizospheres, has been relatively unexplored despite its ubiquity. Previously acknowledged as a common soil bacterium, our research explores its phylogenomics, pangenomics, environmental diversity, and interactions within bacterial communities. By analysing seven genomic sequences, we have identified a pangenome consisting of 19,645 protein families, of which 2644 are shared across all studied genomes, forming the core genome. Interestingly, despite the non-motility of reported isolates, we discovered genes for flagellin and a partial flagellum assembly pathway. Examining the 16S ribosomal RNA genes of Solirubrobacter revealed substantial diversity, with 3166 operational taxonomic units identified in Mexican soils. Co-occurrence network analysis further demonstrated its significant integration within bacterial communities. Through phylogenomic scrutiny, we conclusively excluded the NCBI's GCA_009993245.1 genome from being classified as a Solirubrobacter. Our research into the metagenomic diversity of Solirubrobacter across various environments confirmed its presence in rhizospheres and certain soils, underscoring its adaptability. The geographical ubiquity of Solirubrobacter in rhizospheres raises intriguing questions regarding its potential interactions with plant hosts and the biotic and abiotic factors influencing its presence in soil. Given its ecological significance and genetic diversity, Solirubrobacter warrants further investigation as a potentially crucial yet underappreciated keystone species.

Rhizocola hellebori gen. nov., sp. nov., an actinomycete of the family Micromonosporaceae containing 3,4-dihydroxydiaminopimelic acid in the cell-wall peptidoglycan

An actinomycete strain, K12-0602T, was isolated from the root of a Helleborus orientalis plant in Japan. The 16S rRNA gene sequence of strain K12-0602T showed that it had a close relationship with members of the family Micromonosporaceae and the 16S rRNA gene sequence similarity values between strain K12-0602T and type strains of type species of 27 genera belonging to the family Micromonosporaceae were below 96.2 %. MK-9 (H4) and MK-9 (H6) were detected as major menaquinones, and galactose, xylose, mannose and ribose were present in the whole-cell hydrolysate. The acyl type of the peptidoglycan was glycolyl. Major fatty acids were iso-C15 : 0, iso-C16 : 0, C17 : 1ω9c and anteiso-C17 : 0. Phosphatidylethanolamine was detected as the phospholipid corresponding to phospholipid type II. The G+C content of the genomic DNA was 67 mol%. Analyses of the cell-wall peptidoglycan by TLC and LC/MS showed that it was composed of alanine, glycine, hydroxylglutamic acid and an unknown amino acid, which was subsequently determined to be 3,4-dihydroxydiaminopimelic acid using instrumental analyses, including NMR and mass spectrometry. On the basis of the phylogenetic analysis and chemotaxonomic characteristics, strain K12-0602T represents a novel species of a new genus in the family Micromonosporaceae , for which the name Rhizocola hellebori gen. nov., sp. nov. is proposed. The type strain of the type species is K12-0602T ( = NBRC 109834T = DSM 45988T). This is the first report, to our knowledge, of 3,4-dihydroxydiaminopimelic acid being found as a diamino acid in bacterial cell-wall peptidoglycan.

Wangella harbinensis gen. nov., sp. nov., a new member of the family Micromonosporaceae

A novel endophytic actinomycete, designated strain NEAU-J3(T), was isolated from soybean root (Glycine max (L.) Merr) and characterized using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences suggested that strain NEAU-J3(T) fell within the family Micromonosporaceae. The strain was observed to form an extensively branched substrate mycelium, which carried non-motile oval spores with a smooth surface. The cell walls of strain NEAU-J3(T) were determined to contain meso-diaminopimelic acid and galactose, ribose and glucose were detected as whole-cell sugars. The major menaquinones were determined to be MK-9(H(4)) and MK-9(H(6)). The phospholipids detected were phosphatidylcholine and phosphatidylethanolamine. The major cellular fatty acids were determined to be C(16:0), C(18:1) ω9c, C(18:0), C(17:0), C(17:1) ω7c, anteiso-C(17:0), C(16:1) ω7c and C(15:0). The DNA G + C content was 62.5 mol%. On the basis of the morphological and chemotaxonomic characteristics, phylogenetic analysis and characteristic patterns of 16S rRNA gene signature nucleotides, strain NEAU-J3(T) is considered to represent a novel species of a new genus within the family Micromonosporaceae, for which the name Wangella harbinensis gen. nov., sp. nov. is proposed. The type strain of Wangella harbinensis is strain NEAU-J3(T) (=CGMCC 4.7039(T) = DSM 45747(T)).

Structural insights into the specific anti-HIV property of actinohivin: structure of its complex with the α(1-2)mannobiose moiety of gp120

Actinohivin (AH) is an actinomycete lectin with a potent specific anti-HIV activity. In order to clarify the structural evidence for its specific binding to the α(1-2)mannobiose (MB) moiety of the D1 chains of high-mannose-type glycans (HMTGs) attached to HIV-1 gp120, the crystal structure of AH in complex with MB has been determined. The AH molecule is composed of three identical structural modules, each of which has a pocket in which an MB molecule is bound adopting a bracket-shaped conformation. This conformation is stabilized through two weak C-H...O hydrogen bonds facilitated by the α(1-2) linkage. The binding features in the three pockets are quite similar to each other, in accordance with the molecular pseudo-threefold symmetry generated from the three tandem repeats in the amino-acid sequence. The shape of the pocket can accept two neighbouring hydroxyl groups of the O(3) and O(4) atoms of the equatorial configuration of the second mannose residue. To recognize these atoms through hydrogen bonds, an Asp residue is located at the bottom of each pocket. Tyr and Leu residues seem to block the movement of the MB molecules. Furthermore, the O(1) atom of the axial configuration of the second mannose residue protrudes from each pocket into an open space surrounded by the conserved hydrophobic residues, suggesting an additional binding site for the third mannose residue of the branched D1 chain of HMTGs. These structural features provide strong evidence indicating that AH is only highly specific for MB and would facilitate the highly specific affinity of AH for any glycoprotein carrying many HMTGs, such as HIV-1 gp120.

Xiangella phaseoli gen. nov., sp. nov., a member of the family Micromonosporaceae

A novel endophytic actinomycete, designated strain NEAU-J5(T) was isolated from roots of snap bean (Phaseolus vulgaris L.). Comparative analysis of the 16S rRNA gene sequence indicated that NEAU-J5(T) is phylogenetically related to members of the family Micromonosporaceae. The whole-cell sugars were galactose, mannose and glucose. The predominant menaquinones were MK-9(H4) and MK-9(H6). The major fatty acids were C16:0, C18:0, C17:1ω7c, iso-C15:0 and C17:0. The phospholipids were phosphatidylmethylethanolamine, phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol and phosphatidylinositol mannoside. The DNA G+C content was 72.2 mol%. On the basis of the morphological and chemotaxonomic characteristics, phylogenetic analysis and characteristic patterns of 16S rRNA gene signature nucleotides, strain NEAU-J5(T) represents a novel species of a new genus within the family Micromonosporaceae, for which the name Xiangella phaseoli gen. nov., sp. nov. is proposed. The type strain of Xiangella phaseoli is strain NEAU-J5(T) (=CGMCC 4.7038(T)=DSM 45730(T)).

Crystallographic study of the interaction of the anti-HIV lectin actinohivin with the α(1-2)mannobiose moiety of gp120 HMTG

Actinohivin (AH) is a new potent anti-HIV lectin of microbial origin. In order to modify it to produce a more efficient drug, its three-dimensional structure has previously been determined with and without the target α(1-2)mannobiose moiety of the high-mannose-type glycan (HMTG) attached to HIV-1 gp120. However, ambiguity remained in the structures owing to packing disorder that was possibly associated with peptide fragments attached at the N-terminus. To resolve these problems, the duration of cultivation of the AH-producing strain was examined and it was found that in a sample obtained from a 20 d culture the heterogeneous fragments were completely removed to produce mature AH with high homogeneity. In addition, the purification procedures were simplified in order to increase the yield of AH and the addition of solvents was also examined in order to increase the solubility of AH. AH thus obtained was successfully crystallized with high reproducibility in a different form to the previously obtained crystals. The crystal diffracted well to beyond 1.90 Å resolution and the crystallographic data suggested that it contained no packing disorder.

Diversity and isolation of rare actinomycetes: an overview

A renewed interest in the development of new antimicrobial agents is urgently needed to combat the increasing number of antibiotic-resistant strains of pathogenic microorganisms. Actinomycetes continue to be the mainstream supplier of antibiotics used in industry. The likelihood of discovering a new compound with novel chemical structure can be increased with intensive efforts in isolating and screening of rare genera of microorganisms to include in natural-product-screening collections. An unexpected variety of rare actinomycetes is now being isolated worldwide from previously uninvestigated diverse natural habitats, using different selective isolation methods. These isolation efforts include methods to enhance growth (enrichment) of rare actinomycetes, and eliminate unwanted microorganisms (pretreatment). To speed up the strain isolation process, knowledge about the distribution of such unexploited groups of microorganisms must also be augmented. This is a summary of using these microorganisms as new potential biological resources, and a review of almost all of the selective isolation methods, including pretreatment and enrichment techniques that have been developed to date for the isolation of rare actinomycetes.

Phytomonospora endophytica gen. nov., sp. nov., isolated from the roots of Artemisia annua L

A novel endophytic actinomycete, strain YIM 65646T, was isolated from the roots of Artemisia annua L. collected from Yunnan Province, south-west China. Growth was observed in the temperature range 10–40 °C (optimum 20–28 °C) and at pH 6.0–9.0 (optimum pH 7.0). The organism formed well-developed, branched substrate mycelia, but aerial mycelium was not produced. Phenotypic characterization and 16S rRNA gene sequence analysis indicated that strain YIM 65646T belonged to the family Micromonosporaceae (sharing ≤93.6 % sequence similarity with members of this family) and formed a distinct clade in the Micromonosporaceae phylogenetic tree. The strain contained meso-diaminopimelic acid in the cell wall and mannose, ribose, galactose and glucose in whole-cell hydrolysates. The major menaquinones were MK-10(H4), MK-10(H2), MK-8(H2), MK-9(H2) and MK-10(H6). The major fatty acids were iso-C15 : 0, anteiso-C15 : 0, anteiso-C17 : 0, iso-C17 : 0 and iso-C16 : 0. The DNA G+C content of strain YIM 65646T was 70.0 mol%. On the basis of morphological and chemotaxonomic properties and phylogenetic analysis based on 16S rRNA gene sequence data, it is proposed that this strain should be classified in a novel genus and species, Phytomonospora endophytica gen. nov., sp. nov., in the family Micromonosporaceae. The type strain is YIM 65646T ( = CCTCC AA 209041T  = DSM 45386T).

Allocatelliglobosispora scoriae gen. nov., sp. nov., isolated from volcanic ash

A novel actinomycete, designated strain Sco-B14T, was isolated from volcanic ash collected near Darangshi Oreum (a parasitic or satellite volcano) in Jeju, Republic of Korea. The organism formed well-developed, branched substrate mycelium, on which short chains of non-motile spores were arranged singly or in clusters. Aerial mycelium was not produced. Globose bodies were observed. The reverse colour of colonies was light brown to brown. Diffusible pigments were produced on ISP medium 3 and oatmeal-nitrate agar. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain Sco-B14T formed a lineage within the family Micromonosporaceae and was distinct from established genera. The 16S rRNA gene sequence similarity of strain Sco-B14T to members of related genera of the family was 95.0–95.7 % to type strains of Catellatospora species, 94.7 % to Hamadaea tsunoensis IMSNU 22005T, 94.7 % to Longispora albida K97-0003T and 94.0 % to Catelliglobosispora koreensis LM 042T. 3-Hydroxydiaminopimelic acid was the diagnostic diamino acid in the cell-wall peptidoglycan. Whole-cell sugars were glucose, rhamnose, ribose, xylose, arabinose, galactose and mannose. The polar lipids included diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol. The menaquinone profile contained MK-10(H4) (49 %), MK-9(H4) (24 %), MK-10(H6) (18 %) and MK-9(H6) (9 %). The predominant fatty acids were iso-C15 : 0 and C17 : 0. The DNA G+C content was 70.1 mol%. The combination of chemotaxonomic and phylogenetic data clearly separated the isolate from the type strains of all genera in the family Micromonosporaceae. On the basis of the phylogenetic and chemotaxonomic data presented in this paper, strain Sco-B14T is considered to represent a novel species of a new genus in the family Micromonosporaceae, for which the name Allocatelliglobosispora scoriae gen. nov., sp. nov. is proposed. The type strain of Allocatelliglobosispora scoriae is Sco-B14T (=KCTC 19661T =DSM 45362T).

Phytohabitans suffuscus gen. nov., sp. nov., an actinomycete of the family Micromonosporaceae isolated from plant roots

An actinomycete strain, K07-0523T, was isolated from the roots of an orchid collected in Okinawa prefecture, Japan. 16S rRNA gene sequence analysis indicated that the new strain belonged to the family Micromonosporaceae and the similarity values between strain K07-0523T and the type species of 24 genera in the family Micromonosporaceae were 93.3–97.7 %. Strain K07-0523T contained d-glutamic acid, glycine, d-alanine, meso-diaminopimelic acid, hydroxydiaminopimelic acid and l-lysine in the cell wall. The major menaquinones were MK-9(H6), MK-10(H4) and MK-10(H6). Galactose, glucose, mannose, ribose and xylose were present in the whole-cell sugars. The acyl type of the peptidoglycan was glycolyl. Major fatty acids were anteiso-C17 : 0, iso-C17 : 0, iso-C16 : 0 and iso-C15 : 0. Phosphatidylethanolamine was detected as the major phospholipid and corresponded to phospholipid type II. The G+C content of the genomic DNA was 73 mol%. On the basis of phylogenetic and chemotaxonomic data, the new strain represents a member of a new genus and novel species, namely Phytohabitans suffuscus gen. nov., sp. nov., in the family Micromonosporaceae. The type strain of the type species is K07-0523T (=DSM 45306T=NBRC 105367T).

Jishengella endophytica gen. nov., sp. nov., a new member of the family Micromonosporaceae

A novel endophytic actinomycete, designated strain 202201(T), was isolated from an Acanthus illicifolius root collected from the mangrove reserve zone in Hainan Province, China. Phylogenetic analysis based on 16S rRNA gene sequences suggested that strain 202201(T) fell within the family Micromonosporaceae. The strain formed an extensively branched substrate mycelium, which carried uneven warty-surfaced spores. Cell walls of strain 202201(T) contained meso-diaminopimelic acid and xylose, mannose, arabinose, ribose and glucose were detected as whole-cell sugars. The acyl type of the cell-wall polysaccharides was glycolyl. The major menaquinones were MK-9(H(4)), MK-9(H(6)), MK-9(H(8)) and MK-10(H(4)). The polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol mannoside and phosphatidylserine. The major cellular fatty acids were 10-methyl-C(17 : 0), iso-C(15 : 0), iso-C(16 : 0) and C(17 : 1)ω8c. The DNA G+C content was 72.3 mol%. On the basis of the morphological and chemotaxonomic characteristics, phylogenetic analysis and characteristic patterns of 16S rRNA gene signature nucleotides, strain 202201(T) ( = CGMCC 4.5597(T ) = DSM 45430(T)) represents a novel species of a new genus within the family Micromonosporaceae, for which the name Jishengella endophytica gen. nov., sp. nov. is proposed.

Longispora fulva sp. nov., isolated from a forest soil, and emended description of the genus Longispora

A novel actinomycete, strain KZ0017(T), was isolated from a forest soil collected in Ohnuma, Fukushima, Japan. Strain KZ0017(T) formed spore chains borne on top of short sporophores arising from vegetative hyphae. Spores were non-motile and cylindrical with smooth surfaces. Strain KZ0017(T) contained meso-diaminopimelic (A(2)pm) acid, 3-OH A(2)pm, d-glutamic acid, glycine and l-alanine in the cell-wall peptidoglycan, and xylose, mannose, galactose, rhamnose and ribose in cell-wall hydrolysates. The acyl type of the cell-wall polysaccharides was glycolyl. The predominant menaquinones were MK-10(H(4)) and MK-10(H(6)); MK-10(H(8)) was a minor component. The polar lipids contained diphosphatidylglycerol, phosphatidylethanolamine, hydroxyphosphatidylethanolamine, phosphatidylinositol and several unknown lipids and glycolipids. The major fatty acids were iso-C(16 : 0), 10-methyl-C(17 : 0) and iso-C(17 : 1)ω9c. The DNA G+C content was 70.7 mol%. The 16S rRNA gene sequence of the isolate formed a monophyletic cluster with the single member of the genus Longispora in the family Micromonosporaceae. On the basis of morphological, chemotaxonomic and phylogenetic properties, strain KZ0017(T) represents a novel species of the genus Longispora, for which the name Longispora fulva sp. nov. is proposed; the type strain is KZ0017(T) ( = NBRC 105670(T) = DSM 45356(T)).

Mechanism by which the lectin actinohivin blocks HIV infection of target cells

Various lectins have attracted attention as potential microbicides to prevent HIV transmission. Their capacity to bind glycoproteins has been suggested as a means to block HIV binding and entry into susceptible cells. The previously undescribed lectin actinohivin (AH), isolated by us from an actinomycete, exhibits potent in vitro anti-HIV activity by binding to high-mannose (Man) type glycans (HMTGs) of gp120, an envelope glycoprotein of HIV. AH contains 114 aa and consists of three segments, all of which need to show high affinity to gp120 for the anti-HIV characteristic. To generate the needed mechanistic understanding of AH binding to HIV in anticipation of seeking approval for human testing as a microbicide, we have used multiple molecular tools to characterize it. AH showed a weak affinity to Man alpha(1-2)Man, Man alpha(1-2)Man alpha(1-2)Man, of HMTG (Man8 or Man9) or RNase B (which has a single HMTG), but exhibited a strong and highly specific affinity (K(d) = 3.4 x 10(-8) M) to gp120 of HIV, which contains multiple Man8 and/or Man9 units. We have compared AH to an alternative lectin, cyanovirin-N, which did not display similar levels of discrimination between high- and low-density HMTGs. X-ray crystal analysis of AH revealed a 3D structure containing three sugar-binding pockets. Thus, the strong specific affinity of AH to gp120 is considered to be due to multivalent interaction of the three sugar-binding pockets with three HMTGs of gp120 via the "cluster effect" of lectin. Thus, AH is a good candidate for investigation as a safe microbicide to help prevent HIV transmission.

Actinaurispora siamensis gen. nov., sp. nov., a new member of the family Micromonosporaceae

Two actinomycete strains, CM2-8(T) and CM2-12, were isolated from temperate peat swamp forest soil in Chiang Mai Province, Thailand. Their taxonomic positions were determined using a polyphasic approach. Chemotaxonomic characteristics of these strains coincided with those of the family Micromonosporaceae, i.e. cell wall chemotype II, N-glycolyl type of muramic acid, and type II phospholipids. Phylogenetic analysis based on 16S rRNA gene sequence data also indicated that these strains fell within the family Micromonosporaceae and formed a distinct taxon in the Micromonosporaceae phylogenetic tree. On the basis of phylogenetic analysis, characteristic patterns of 16S rRNA gene signature nucleotides and chemotaxonomic data, it is proposed that the novel isolates belong to a new genus, Actinaurispora gen. nov. The type species of the genus is proposed as Actinaurispora siamensis sp. nov., with strain CM2-8(T) (=JCM 15677(T)=BCC 34762(T)) as the type strain.

Plantactinospora mayteni gen. nov., sp. nov., a member of the family Micromonosporaceae

A novel Gram-positive, aerobic, spore-forming, endophytic actinomycete, designated strain YIM 61359(T), was isolated from the roots of Maytenus austroyunnanensis plants collected from tropical rainforest in Xishuangbanna, Yunnan Province, south-west China. The strain formed single or cluster spores with smooth surfaces from substrate mycelia. The strain contained meso-diaminopimelic acid in the cell wall and arabinose, xylose, galactose and glucose in whole-cell hydrolysates. The acyl type of the cell-wall polysaccharides was glycolyl. MK-10(H(6)), MK-10(H(8)) and MK-10(H(4)) were the predominant menaquinones. The polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylinositol and several unknown phospholipids. The major fatty acids were iso-C(15 : 0), anteiso-C(15 : 0), C(17 : 0), anteiso-C(17 : 0) and iso-C(16 : 0). The DNA G+C content of strain YIM 61359(T) was 69.7 mol%. These chemotaxonomic data indicated that the strain belongs to the family Micromonosporaceae. Phylogenetic analysis based on 16S rRNA gene sequences also suggested that strain YIM 61359(T) fell within the family Micromonosporaceae. On the basis of morphological and chemotaxonomic data, phylogenetic analysis and characteristic patterns of 16S rRNA gene signature nucleotides, strain YIM 61359(T) is considered to represent a novel species of a new genus within the family Micromonosporaceae, for which the name Plantactinospora mayteni gen. nov., sp. nov. is proposed. The type strain of Plantactinospora mayteni is YIM 61359(T) (=CCTCC AA 208022(T)=DSM 45238(T)).

An update of the structure and 16S rRNA gene sequence-based definition of higher ranks of the class Actinobacteria, with the proposal of two new suborders and four new families and emended descriptions of the existing higher taxa

The higher ranks of the class Actinobacteria were proposed and described in 1997. At each rank, the taxa were delineated from each other solely on the basis of 16S rRNA gene sequence phylogenetic clustering and taxon-specific 16S rRNA signature nucleotides. In the past 10 years, many novel members have been assigned to this class while, at the same time, some members have been reclassified. The new 16S rRNA gene sequence information and the changes in phylogenetic positions of some taxa influence decisions about which 16S rRNA nucleotides to define as taxon-specific. As a consequence, the phylogenetic relationships of Actinobacteria at higher levels may need to be reconstructed. Here, we present new 16S rRNA signature nucleotide patterns of taxa above the family level and indicate the affiliation of genera to families. These sets replace the signatures published in 1997. In addition, Actinopolysporineae subord. nov. and Actinopolysporaceae fam. nov. are proposed to accommodate the genus Actinopolyspora, Kineosporiineae subord. nov. and Kineosporiaceae fam. nov. are proposed to accommodate the genera Kineococcus, Kineosporia and Quadrisphaera, Beutenbergiaceae fam. nov. is proposed to accommodate the genera Beutenbergia, Georgenia and Salana and Cryptosporangiaceae fam. nov. is proposed to accommodate the genus Cryptosporangium. The families Nocardiaceae and Gordoniaceae are proposed to be combined in an emended family Nocardiaceae. Emended descriptions are also proposed for most of the other higher taxa.

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)).

Structural variation in the glycan strands of bacterial peptidoglycan

The normal, unmodified glycan strands of bacterial peptidoglycan consist of alternating residues of beta-1,4-linked N-acetylmuramic acid and N-acetylglucosamine. In many species the glycan strands become modified after their insertion into the cell wall. This review describes the structure of secondary modifications and of attachment sites of surface polymers in the glycan strands of peptidoglycan. It also provides an overview of the occurrence of these modifications in various bacterial species. Recently, enzymes responsible for the N-deacetylation, N-glycolylation and O-acetylation of the glycan strands were identified. The presence of these modifications affects the hydrolysis of peptidoglycan and its enlargement during cell growth. Glycan strands are frequently deacetylated and/or O-acetylated in pathogenic species. These alterations affect the recognition of bacteria by host factors, and contribute to the resistance of bacteria to host defence factors such as lysozyme.

Luedemannella gen. nov., a new member of the family Micromonosporaceae and description of Luedemannella helvata sp. nov. and Luedemannella flava sp. nov

Three actinomycete strains were isolated from soil samples collected in Bangladesh. The cultures formed spherical sporangia on short sporangiophores directly above the surface of the substrate mycelium. The sporangia developed singly or in clusters and each sporangium contained several nonmotile spherical to oval spores with a smooth surface. The strains 3-9(24)(T), 3-21(27) and 7-40(26)(T) contained meso-diaminopimelic acid in the cell walls, predominant menaquinone MK-9(H(6)) and MK-9(H(4)) and glucose, xylose, galactose, mannose, rhamnose, ribose and arabinose in the whole-cell hydrolysates. Diagnostic phospholipid is phosphatidylethanolamine and branched anteiso-C(17 : 0) (30.0-38.0%), anteiso-C(15 : 0) (12.5-14.0%), iso-C(16 : 0) (10.0-15.0%) and iso-C(15 : 0) (10.0-12.0%) 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 71 mol%. The chemotaxonomic data indicate that these strains belong to the family Micromonosporaceae. Phylogenetic analysis based on 16S rRNA gene sequence data suggested that the strains 3-9(24)(T), 3-21(27) and 7-40(26)(T) fall within the family Micromonosporaceae. On the basis of phylogenetic analysis and characteristic patterns of signature nucleotides as well as morphological and chemotaxonomic data, Luedemannella gen. nov. is proposed for our 3 isolates. DNA-DNA hybridization experiment and phenotypic characterization indicated that the new genus was constituted of 2 species, as Luedemannella helvata sp. nov. for the strain 3-9(24)(T) (=JCM 13249(T)=MTCC 8091(T)) and Luedemannella flava for the strain 7-40(26)(T) (=JCM 13250(T)=MTCC 8095(T)) in the family Micromonosporaceae.

A new genus of the family Micromonosporaceae, Polymorphospora gen. nov., with description of Polymorphospora rubra sp. nov

Two actinomycete strains were isolated from soil surrounding mangrove roots. The isolates formed short spore chains with spores showing diverse shapes. The isolates contained glutamic acid, glycine, alanine and meso-diaminopimelic acid in the cell wall, 3-O-methylmannose, mannose, galactose and glucose as the whole-cell sugars and MK-10(H6), MK-10(H4), MK-9(H6) and MK-9(H4) as the predominant isoprenoid quinones. The isolates formed a distinct taxon in the phylogenetic tree of the Micromonosporaceae based on analysis of 16S rRNA gene sequences and showed chemical and phenotypic properties that were different from members of all of the other genera of this family. Based on these observations, it is proposed that the novel isolates belong to a new genus, Polymorphospora gen. nov. The type species of the genus is proposed as Polymorphospora rubra sp. nov., with strain TT 97-42T (=NBRC 101157T=DSM 44947T) as the type strain.

Actinocatenispora thailandica gen. nov., sp. nov., a new member of the family Micromonosporaceae

Two actinomycete strains, TT2-10T and TT2-3, which produced long spore chains (more than 10 spores per chain), were isolated from peat swamp forest soil in Pattaloong Province, Thailand. Their taxonomic positions were determined using a polyphasic approach. The chemotaxonomic characteristics of these strains coincided with those of the family Micromonosporaceae, i.e. cell-wall chemotype II, muramic acid of the N-glycolyl type, whole-cell sugar pattern D and type II phospholipids. Analysis of the 16S rRNA gene sequences also indicated that these strains constitute a distinct lineage within the family Micromonosporaceae, sharing 91.3–93.8 % sequence similarity with members of this family. On the basis of their phenotypic and genotypic characteristics and their phylogenetic position, these strains represent a novel genus and species, for which the name Actinocatenispora thailandica gen. nov., sp. nov. is proposed. The type strain of Actinocatenispora thailandica is strain TT2-10T (=JCM 12343T=PCU 235T=DSM 44816T).

New medicines from nature's armamentarium

Nature frequently unleashes a barrage of new and frightening diseases against humans--such as HIV, severe acquired respiratory syndrome, Ebola virus and avian flu recently--in addition to the seemingly ever-present scourges such as malaria and tuberculosis. Fortunately, nature also provides the wherewithal to help conquer the diseases that it sets loose. All that is needed is the human ingenuity to discover, develop and apply the solutions in an optimal fashion. Participants at the 9th Max Tishler Memorial Symposium (Tokyo, July 2005) were told about several new advances in the search for new anti-infective drugs derived from natural sources and were able to learn how one of the most effective drugs ever, ivermectin, made its way through what was, at the time, uncharted territory and how precedents were set at nearly every stage to form a model for all subsequent public-private partnerships.

Salinispora arenicola gen. nov., sp. nov. and Salinispora tropica sp. nov., obligate marine actinomycetes belonging to the family Micromonosporaceae

A taxonomic study was carried out to clarify the taxonomy of representatives of a group of marine actinomycetes previously designated MAR 1 and considered to belong to the family Micromonosporaceae. The organisms had phenotypic properties consistent with their assignment to this taxon. The strains formed a distinct taxon in the 16S rRNA Micromonosporaceae gene tree and shared a range of phenotypic properties that distinguished them from members of all of the genera with validly published names classified in this family. The name proposed for this novel taxon is Salinispora gen. nov. The genus contains two species recognized using a range of genotypic and phenotypic criteria, including comparative 16S-23S rRNA gene spacer region and DNA-DNA relatedness data. The names proposed for these taxa are Salinispora arenicola sp. nov., the type species, and Salinispora tropica sp. nov.; the type strains of these novel species have been deposited in service culture collections as strain CNH-643(T) (=ATCC BAA-917(T)=DSM 44819(T)) and strain CNB-440(T) (=ATCC BAA-916(T)=DSM 44818(T)), respectively.

Essential regions for antiviral activities of actinohivin, a sugar-binding anti-human immunodeficiency virus protein from an actinomycete

Actinohivin (AH) is a potent anti-human immunodeficiency virus (HIV) protein that consists of highly conserved three-tandem repeats (segments 1, 2, and 3). The molecular target of AH in its anti-HIV activity is high-mannose-type saccharide chains of HIV gp120. This article deals with sequence requirements for the anti-HIV activity of AH. The deleted or substituted DNAs encoding AH or His-AH were prepared using mutagenic oligonucleotide primers in PCR. The mutant constructs were expressed in Escherichia coli, and the activities of the recombinant protein products were examined by a syncytium-formation assay system that mimics anti-HIV activity. The single segment mutant His-AHs showed no anti-syncytium-formation activity, but the mutant His-AHs, which consists of 2 or 3 segments, retained reduced activities. His-AH(6-114) dramatically reduced the anti-syncytium-formation activity to that of His-AH(36-114) or His-AH(I5A). Furthermore, His-AH(Q33A), His-AH(Q71A), and His-AH(Q109A) in which glutamine residues were substituted into alanine showed reduced activities of 1/20, 1/10, and 1/30, respectively, in anti-syncytium formation compared with His-AH. These results indicate that three segments of AH are necessary for potent anti-syncytium-formation activity-that is, for potent anti-HIV activity and the cooperated involvement of each segment of AH increased the AH-gp120 interaction.

Isolation and characterization of novel marine-derived actinomycete taxa rich in bioactive metabolites

A unique selective enrichment procedure has resulted in the isolation and identification of two new genera of marine-derived actinobacteria. Approximately 90% of the microorganisms cultured by using the presented method were from the prospective new genera, a result indicative of its high selectivity. In this study, 102 actinomycetes were isolated from subtidal marine sediments collected from the Bismarck Sea and the Solomon Sea off the coast of Papua New Guinea. A combination of physiological parameters, chemotaxonomic characteristics, distinguishing 16S rRNA gene sequences, and phylogenetic analysis based on 16S rRNA genes provided strong evidence for the two new genera (represented by strains of the PNG1 clade and strain UMM518) within the family Micromonosporaceae. Biological activity testing of fermentation products from the new marine-derived actinomycetes revealed that several had activities against multidrug-resistant gram-positive pathogens, malignant cells, and vaccinia virus replication.

Actinohivin, a novel anti-human immunodeficiency virus protein from an actinomycete, inhibits viral entry to cells by binding high-mannose type sugar chains of gp120

We searched human immunodeficiency virus (HIV) entry inhibitors and found a novel anti-HIV protein, actinohivin (AH), in a culture filtrate of the newly discovered genus actinomycete Longispora albida gen. nov., sp. nov. This paper deals with the mechanism of action of the anti-HIV activity of AH. AH exhibited potent anti-HIV activities against various strains of HIV-1 and HIV-2. AH bound to the glycoprotein gp120 of various strains of HIV-1 and gp130 of simian immunodeficiency virus (SIV), but did not bind to non-glycosylated gp120 nor to cells having CD4 and coreceptors, suggesting that AH inhibits viral entry to cells by binding to the envelope glycoprotein. The investigation of the effects of various sugars on AH-gp120 binding by ELISA revealed that yeast mannan alone strongly inhibited the binding (IC50 = 3.0 microg/ml). Experiments investigating the binding of AH to other glycoproteins revealed that AH binds to ribonuclease B and thyroglobulin that have a high-mannose type saccharide chain, but not to other glycoproteins having a N-glycoside type saccharide chain. The above results indicate that high-mannose type saccharide chains of gp120 are molecular targets of AH in its anti-HIV activity.

Isolation of new actinomycete strains for the screening of new bioactive compounds

In order to facilitate the discovery of novel bioactive compounds from microorganisms, various techniques for isolation of new actinomycete strains have been attempted. Studies of the vertical distribution of actinomycetes in soil, isolation of actinomycetes from desert soils or fallen leaves, selective isolation of Kitasatospora strains using novobiocin or Actinoplanes strains using the chemotactic method, and the use of gellan gum as a solidifying agent were carried out. We discovered 9 novel bioactive compounds from actinomycete strains isolated under unusual conditions, and proposed two new genera, five new species and one new subspecies.