Seven new 3,4,6-trisubstituted α-pyrone derivatives, violapyrones A-G (1-7), were isolated from Streptomyces violascens obtained from Hylobates hoolock feces. Their structures were elucidated on the basis of detailed spectroscopic analysis. The antimicrobial activities of 1-7 were evaluated against Gram-positive and Gram-negative bacteria and against fungi. Compounds 1-3 showed moderate antibacterial activities against Bacillus subtilis and Staphylococcus aureus with MIC values of 4-32 μg/mL.
Summary
Heterologous expression of a biosynthesis gene cluster from
Amycolatopsis
sp. resulted in the discovery of two unique class IV lasso peptides, felipeptins A1 and A2. A mixture of felipeptins stimulated proliferation of cancer cells, while having no such effect on the normal cells. Detailed investigation revealed, that pre-treatment of cancer cells with a mixture of felipeptins resulted in downregulation of the tumor suppressor Rb, making the cancer cells to proliferate faster. Pre-treatment with felipeptins made cancer cells considerably more sensitive to the anticancer agent doxorubicin and re-sensitized doxorubicin-resistant cells to this drug. Structural characterization and binding experiments showed an interaction between felipeptins resulting in complex formation, which explains their synergistic effect. This discovery may open an alternative avenue in cancer treatment, helping to eliminate quiescent cells that often lead to cancer relapse.
Two Gram-positive, aerobic actinomycete strains, designated YIM 48771 T and YIM 48782 T , were isolated from virgin forest soil samples collected in Hunan Province, China. 16S rRNA gene sequence similarities of the two novel isolates ranged from 96.3 to 97.6 % with species of the genus Sphaerisporangium with validly published names but, in the tree based on 16S rRNA gene sequences, the isolates formed distinct phyletic lines. The level of 16S rRNA gene sequence similarity between the two novel isolates was 97.1 %. DNA-DNA hybridization of strains YIM 48771 T and YIM 48782 T with recognized species of the genus Sphaerisporangium revealed that the level of DNA-DNA relatedness was below 70 %. The DNA G+C contents of strains YIM 48771 T and YIM 48782 T were 67.1 and 71 mol%, respectively. Chemotaxonomic data [major menaquinone, MK-9(H 4 ); major polar lipids, diphosphatidylglycerol, phosphatidylinositol mannoside, phosphatidylethanolamine and phosphoglycolipids; major fatty acids, iso-C 16 : 0 and 10-methyl C 17 : 0 ] supported the affiliation of the two isolates with the genus Sphaerisporangium. The results of DNA-DNA hybridization and physiological and biochemical tests allowed genotypic and phenotypic differentiation of the two isolates from recognized Sphaerisporangium species. Based on morphological, chemotaxonomical and phylogenetic data, strains YIM 48771 T and YIM 48782 T are considered to represent two novel species of the genus Sphaerisporangium, for which the names Sphaerisporangium flaviroseum sp. nov. (type strain, YIM 48771 T 5DSM 45170 T 5KCTC 19393 T ) and Sphaerisporangium album sp. nov. (type strain, YIM 48782 T 5DSM 45172 T 5CCTCC AA 208026 T ) are proposed.
A Gram-positive, non-spore-forming actinomycete, designated strain CC 0387 T , was isolated from a sediment sample from the Baltic Sea, Germany. Classification using a polyphasic approach and comparative 16S rRNA gene sequencing showed that strain CC 0387 T belonged to the genus Promicromonospora and displayed more than 3 % 16S rRNA gene sequence divergence from all Promicromonospora species with validly published names. Strain CC 0387 T did not produce aerial mycelium. Substrate mycelia were yellowish white to pale orange-yellow and fragmented into bacillary or coccoid elements. The cell wall contained lysine and alanine. Wholecell hydrolysates contained galactose, glucose, rhamnose and ribose. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, an unknown phospholipid and an unknown glycolipid. The predominant menaquinone was MK-9(H 4 ) (86 %). The G+C content of the DNA was 71.87 mol%. Based on morphological, chemotaxonomic, phenotypic and genetic characteristics, strain CC 0387 T (5CCTCC AA208024 T 5DSM 21481 T
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