Discovery of an unprecedented benz[α]anthraquinone-type heterodimer from a rare actinomycete Amycolatopsis sp. HCa1.

The angucylines are a family of aromatic polyketides featuring a tetracyclic benz[a]anthraquinone skeleton. This class of polycyclic aromatic polyketides are exclusively associated with actinomycetes and can undergo many modifications such as oxidation, ring cleavage, glycosylation and dimerization. Here we report the discovery of a new ether-linked benz[a]anthraquinone heterodimer, named mycolatone (1), from a grasshopper-derived actinomycete, Amycolatopsis sp. HCa1. The structure of mycolatone (1) was determined by comprehensive two-dimensional NMR analysis, high-resolution electrospray ionization mass spectrometry and biogenetic consideration. This new heterodimeric molecule is structurally derived from the dimerization of two tetracyclic angucylines, 2-hydroxy-5-O-methyltetragomycin and PD116779, through an ether bond between C-8 and C-8'. This new structural feature enrich the structural diversity of angucylines. Additionally, the surface tension activity and cytotoxic activities of 1 against human cervical cancer cell line (Hela), human gastric adenocarcinoma cell line (SGC-7901) and human lung adenocarcinoma cell line (SPC-A-1) were evaluated.

Microparticles enhance the formation of seven major classes of natural products in native and metabolically engineered actinobacteria through accelerated morphological development.

Actinobacteria provide a rich spectrum of bioactive natural products and therefore display an invaluable source towards commercially valuable pharmaceuticals and agrochemicals. Here, we studied the use of inorganic talc microparticles (hydrous magnesium silicate, 3MgO·4SiO2 ·H2 O, 10 µm) as a general supplement to enhance natural product formation in this important class of bacteria. Added to cultures of recombinant Streptomyces lividans, talc enhanced production of the macrocyclic peptide antibiotic bottromycin A2 and its methylated derivative Met-bottromycin A2 up to 109 mg L-1 , the highest titer reported so far. Hereby, the microparticles fundamentally affected metabolism. With 10 g L-1 talc, S. lividans grew to 40% smaller pellets and, using RNA sequencing, revealed accelerated morphogenesis and aging, indicated by early upregulation of developmental regulator genes such as ssgA, ssgB, wblA, sigN, and bldN. Furthermore, the microparticles re-balanced the expression of individual bottromycin cluster genes, resulting in a higher macrocyclization efficiency at the level of BotAH and correspondingly lower levels of non-cyclized shunt by-products, driving the production of mature bottromycin. Testing a variety of Streptomyces species, talc addition resulted in up to 13-fold higher titers for the RiPPs bottromycin and cinnamycin, the alkaloid undecylprodigiosin, the polyketide pamamycin, the tetracycline-type oxytetracycline, and the anthramycin-analogs usabamycins. Moreover, talc addition boosted production in other actinobacteria, outside of the genus of Streptomyces: vancomycin (Amycolatopsis japonicum DSM 44213), teicoplanin (Actinoplanes teichomyceticus ATCC 31121), and the angucyclinone-type antibiotic simocyclinone (Kitasatospora sp.). For teicoplanin, the microparticles were even crucial to activate production. Taken together, the use of talc was beneficial in 75% of all tested cases and optimized natural and heterologous hosts forming the substance of interest with clusters under native and synthetic control. Given its simplicity and broad benefits, microparticle-supplementation appears as an enabling technology in natural product research of these most important microbes.

A new phthalazinone derivative and a new isoflavonoid glycoside from lichen-associated Amycolatopsis sp.

A new phthalazinone derivative, named amycophthalazinone A (1), and a new isoflavonoid glycoside, 7-O-methyl-5-O-α-L-rhamnopyranosylgenestein (2), along with an isoflavonoid glycoside, 7-O-α-D-arabinofuranosyl daidzein (3) firstly found from natural sources, and eight known compounds (4-11), were isolated from the culture broth of the lichen-associated Amycolatopsis sp. YIM 130642. The structures of new compounds were elucidated on the basis of spectroscopic analysis. Compound 1 was the first example of naturally occurring phthalazinone derivative. The antimicrobial activities of all compounds towards five pathogenic strains were evaluated by a broth microdilution assay. Compound 1 exhibited the most potent inhibitory activity against Staphylococcus aureus, Salmonella typhi, and Candida albicans with MIC values of 32, 32, and 64 µg/mL, respectively.

Amycolatopsis antarctica sp. nov., isolated from the surface of an Antarctic brown macroalga.

Two moderately psychrophilic actinobacterial strains, designated AU-G6T and AU-A3.2, isolated from the surface of an Antarctic macroalga, Adenocystis utricularis (Bory) Skottsberg, was taxonomically characterized based on a polyphasic investigation. The two strains had nearly identical 16S rRNA gene sequences and formed a distinct phyletic line within the genus Amycolatopsis of the family Pseudonocardiaceae. They were phylogenetically close to Amycolatopsis nigrescens JCM 14717T, Amycolatopsis minnesotensis JCM 14545T and Amycolatopsis magusensis DSM 45510T, with 16S rRNA gene sequence similarities of 97.77, 97.20 and 97.19 %, respectively. Phylogenomic analysis based on the whole genome data supported that strain AU-G6T was distantly related to the Amycolatopsis species. The isolates shared a range of phenotypic markers typical of members of the genus Amycolatopsis, but also had a range of cultural, physiological and biochemical characteristics that separated them from related Amycolatopsis species. The isolates showed growth only in media supplemented with salt, indicating their marine origin. The cell wall of the isolates contained meso-diaminopimelic acid, and arabinose and galactose were detected as diagnostic sugars (type IV). The main menaquinone was MK-9(H4). The main polar lipids were phosphatidylethanolamine, hydroxy-phosphotidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol (type II). The fatty acid type was 3c. The combined genotypic and phenotypic data indicated that the two isolates represent a novel species of the genus Amycolatopsis. The name proposed for this species is Amycolatopsis antarctica sp. nov., with type strain AU-G6T (=CGMCC 4.7351T=NBRC 112404T).

Actinobacteria possessing antimicrobial and antioxidant activities isolated from the pollen of scots pine (Pinus sylvestris) grown on the Baikal shore.

Isolated ecosystems existing under specific environmental conditions have been shown to be promising sources of new strains of actinobacteria. The taiga forest of Baikal Siberia has not been well studied, and its actinobacterial population remains uncharacterized. The proximity between the huge water mass of Lake Baikal and high mountain ranges influences the structure and diversity of the plant world in Siberia. Here, we report the isolation of eighteen actinobacterial strains from male cones of Scots pine trees (Pinus sylvestris) growing on the shore of the ancient Lake Baikal in Siberia. In addition to more common representative strains of Streptomyces, several species belonging to the genera Rhodococcus, Amycolatopsis, and Micromonospora were isolated. All isolated strains exhibited antibacterial and antifungal activities. We identified several strains that inhibited the growth of the pathogen Candida albicans but did not hinder the growth of Saccharomyces cerevisiae. Several isolates were active against Gram-positive and Gram-negative bacteria. The high proportion of biologically active strains producing antibacterial and specific antifungal compounds may reflect their role in protecting pollen against phytopathogens.

Siderochelins with anti-mycobacterial activity from Amycolatopsis sp. LZ149.

Three new compounds, namely siderochelins D (2), E (3), and F (4), together with one known siderochelin A (1), were isolated from Amycolatopsis sp. LZ149 and elucidated by spectroscopic analyses including1D- and 2D-NMR and X-ray single crystal diffraction. Compounds 1-3 showed antibacterial activity against Mycobacterium smegmatis.