Asanoa iriomotensis sp. nov., isolated from mangrove soil

Asanoa endophytica sp. nov., an endophytic actinomycete isolated from the rhizome of Boesenbergia rotunda

A novel Gram-stain-positive, non-motile, endophytic actinomycete, designated strain BR3-1^T, which produced spore chains borne on the tips of short sporophores, was isolated from the rhizome of Boesenbergia rotunda collected from Udon Thani province, Thailand. This strain was investigated for its taxonomic position using a polyphasic approach. The strain contained 3-hydroxydiaminopimelic acid and meso-diaminopimelic acid in the cell-wall peptidoglycan. The whole-cell sugars comprised glucose, mannose, rhamnose, ribose and xylose. Phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylinositol and phosphatidylinositol mannosides were found as the characteristic phospholipids. The predominant menaquinones were MK-10(H₈) and MK-10(H₆). The major cellular fatty acids were iso-C_16 : 0, iso-C_15 : 0 and anteiso-C_15 : 0. The G+C content of the genomic DNA was 71.4 mol%. 16S rRNA gene sequence analysis revealed that strain BR3-1^T belonged to the genus Asanoa and was most closely related to Asanoa ishikariensis (99.39 %), Asanoa iriomotensis (99.31 %), Asanoa siamensis (99.17 %), Asanoa ferruginea (98.84 %) and Asanoa hainanensis (98.71 %). The DNA-DNA relatedness value between strain BR3-1^T and its phylogenetically closest relatives was in the range of 15.4 % ± 1.2 to 45.8 % ± 2.6. In addition, some physiological and biochemical properties indicated that strain BR3-1^T could be readily distinguished from all type strains in the genus Asanoa. Thus, strain BR3-1^T should be classified as a representative of a novel species, for which the name Asanoa endophytica sp. nov. is proposed. The type strain is BR3-1^T ( = BCC 66355^T = NBRC 110002^T).

Mangrove rare actinobacteria: taxonomy, natural compound, and discovery of bioactivity

Actinobacteria are one of the most important and efficient groups of natural metabolite producers. The genus Streptomyces have been recognized as prolific producers of useful natural compounds as they produced more than half of the naturally-occurring antibiotics isolated to-date and continue as the primary source of new bioactive compounds. Lately, Streptomyces groups isolated from different environments produced the same types of compound, possibly due to frequent genetic exchanges between species. As a result, there is a dramatic increase in demand to look for new compounds which have pharmacological properties from another group of Actinobacteria, known as rare actinobacteria; which is isolated from special environments such as mangrove. Recently, mangrove ecosystem is becoming a hot spot for studies of bioactivities and the discovery of natural products. Many novel compounds discovered from the novel rare actinobacteria have been proven as potential new drugs in medical and pharmaceutical industries such as antibiotics, antimicrobials, antibacterials, anticancer, and antifungals. This review article highlights the latest studies on the discovery of natural compounds from the novel mangrove rare actinobacteria and provides insight on the impact of these findings.

Asanoa siamensis sp. nov., isolated from soil from a temperate peat swamp forest

A novel actinomycete strain, PS7-2T, which produced spore chains borne on the tips of short sporophores, was isolated from soil collected from a temperate peat swamp forest in Phu-Sang National Park, Phayao province, Thailand. The isolate contained glutamic acid, glycine, alanine, 3-hydroxy-diaminopimelic acid and meso-diaminopimelic acid in the cell-wall peptidoglycan. The whole-cell sugars were glucose, mannose, rhamnose and xylose, and the major phospholipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and phosphatidylethanolamine. The predominant menaquinones were MK-10(H8) and MK-9(H8) and the predominant cellular fatty acids were iso-C15 : 0, anteiso-C15 : 0 and anteiso-C17 : 0. The G+C content of the genomic DNA was 72.3 mol%. On the basis of 16S rRNA gene sequence analysis, strain PS7-2T clustered with members of the genus Asanoa and appeared most closely related to the type strains of Asanoa hainanensis (99.5 % sequence similarity), Asanoa iriomotensis (99.0 %), Asanoa ishikariensis (98.9 %) and Asanoa ferruginea (98.5 %). DNA–DNA hybridizations and some physiological and biochemical properties indicated that strain PS7-2T could be readily distinguished from its closest phylogenetic relatives. Based on the phenotypic and genotypic evidence and DNA–DNA relatedness values, strain PS7-2T represents a novel species in the genus Asanoa , for which the name Asanoa siamensis sp. nov. is proposed; the type strain is PS7-2T ( = BCC 41921T = NBRC 107932T).

Diversity and biosynthetic potential of culturable actinomycetes associated with marine sponges in the China Seas

The diversity and secondary metabolite potential of culturable actinomycetes associated with eight different marine sponges collected from the South China Sea and the Yellow sea were investigated. A total of 327 strains were isolated and 108 representative isolates were selected for phylogenetic analysis. Ten families and 13 genera of Actinomycetales were detected, among which five genera represent first records isolated from marine sponges. Oligotrophic medium M5 (water agar) proved to be efficient for selective isolation, and “Micromonospora–Streptomyces” was proposed as the major distribution group of sponge-associated actinomycetes from the China Seas. Ten isolates are likely to represent novel species. Sponge Hymeniacidon perleve was found to contain the highest genus diversity (seven genera) of actinomycetes. Housekeeping gene phylogenetic analyses of the isolates indicated one ubiquitous Micromonospora species, one unique Streptomyces species and one unique Verrucosispora phylogroup. Of the isolates, 27.5% displayed antimicrobial activity, and 91% contained polyketide synthase and/or nonribosomal peptide synthetase genes, indicating that these isolates had a high potential to produce secondary metabolites. The isolates from sponge Axinella sp. contained the highest presence of both antimicrobial activity and NRPS genes, while those from isolation medium DNBA showed the highest presence of antimicrobial activity and PKS I genes.

Asanoa hainanensis sp. nov., isolated from rhizosphere soil of Acrostichum speciosum in a mangrove, and emended description of the genus Asanoa

A Gram-reaction-positive, non-motile actinobacterium, designated strain 210121T, was isolated from rhizosphere soil of the mangrove fern Acrostichum speciosum. 16S rRNA gene sequence analysis showed that the isolate belonged to the genus Asanoa. DNA–DNA relatedness values between strain 210121T and the type strains of the three recognized species of the genus Asanoa were below the 70 % threshold recommended for distinguishing bacterial genomic species. The novel isolate contained glutamic acid, glycine, alanine and meso-A2pm as cell-wall amino acids, indicating peptidoglycan type A1γ. The characteristic whole-cell sugars were xylose, ribose, glucose and mannose. The predominant menaquinones were MK-9(H4), MK-9(H6) and MK-9(H8). The major fatty acids were iso-C16 : 0 (30.9 %), C17 : 0 (23.0 %), anteiso-C15 : 0 (14.9 %) and iso-C15 : 0 (12.3 %). The phospholipid profile comprised phosphatidylethanolamine, phosphatidylinositol mannosides and phospholipids of unknown structure containing glucosamine. The G+C content of the DNA was 70.3 mol%. On the basis of the phenotypic and genotypic data, strain 210121T ( = CGMCC 4.5593T  = DSM 45427T) represents a novel species of the genus Asanoa, for which the name Asanoa hainanensis sp. nov., is proposed. An emended description of the genus Asanoa is also proposed.

Actinomycetes for marine drug discovery isolated from mangrove soils and plants in China

The mangrove ecosystem is a largely unexplored source for actinomycetes with the potential to produce biologically active secondary metabolites. Consequently, we set out to isolate, characterize and screen actinomycetes from soil and plant material collected from eight mangrove sites in China. Over 2,000 actinomycetes were isolated and of these approximately 20%, 5%, and 10% inhibited the growth of Human Colon Tumor 116 cells, Candida albicans and Staphylococcus aureus, respectively, while 3% inhibited protein tyrosine phosphatase 1B (PTP1B), a protein related to diabetes. In addition, nine isolates inhibited aurora kinase A, an anti-cancer related protein, and three inhibited caspase 3, a protein related to neurodegenerative diseases. Representative bioactive isolates were characterized using genotypic and phenotypic procedures and classified to thirteen genera, notably to the genera Micromonospora and Streptomyces. Actinomycetes showing cytotoxic activity were assigned to seven genera whereas only Micromonospora and Streptomyces strains showed anti-PTP1B activity. We conclude that actinomycetes isolated from mangrove habitats are a potentially rich source for the discovery of anti-infection and anti-tumor compounds, and of agents for treating neurodegenerative diseases and diabetes.