Generation of landomycin D-producing strainStreptomyces globisporus LD3

Landomycin biosynthesis and its regulation in Streptomyces

This mini-review is centered on genetic aspects of biosynthesis of landomycins (La), a family of angucycline polyketides. From the very discovery in the 1990s, La were noted for unusual structure and potent anticancer properties. La are produced by a few actinobacteria that belong to genus Streptomyces. Biochemical logic behind the production of La aglycon and glycoside halves and effects of La on mammalian cells have been thoroughly reviewed in 2009-2012. Yet, the genetic diversity of La biosynthetic gene clusters (BGCs) and regulation of their production were not properly reviewed since discovery of La. Here, we aim to fill this gap by focusing on three interrelated topics. First, organization of known La BGCs is compared. Second, up-to-date scheme of biosynthetic pathway to landomycin A (LaA), the biggest (by molar weight) member of La family, is succinctly outlined. Third, we describe genetic and nutritional factors that influence La production and export. A summary of the practical utility of the gained knowledge and future directions to study La biosynthesis conclude this mini-review.

Streptomyces sundarbansensis sp. nov., an actinomycete that produces 2-allyloxyphenol

A novel actinomycete producing 2-allyloxyphenol, designated strain MS1/7(T), was isolated from sediments of the Sundarbans mangrove forest, India. Growth on International Streptomyces Project (ISP) media 2, 3, 4, 5 and 7 produced olive green to grey aerial hyphae that carried smooth-surfaced spores in a flexuous (Rectiflexibiles) arrangement. The strain contained ll-diaminopimelic acid, but no diagnostic sugars in whole-cell hydrolysates. Hexa-, octa- and a minor amount of tetra-hydrogenated menaquinones with nine isoprene units [MK-9 (H(4), H(6), H(8) and H(10))] were present as isoprene analogues. Diagnostic phospholipids were phosphatidylethanolamine and diphosphatidylglycerol. The predominant fatty acids were anteiso-C(15 : 0) (34.80 %), iso-C(16 : 0) (16.45 %), C(16) (10.53 %) and anteiso-C(17 : 0) (10.92 %). The strain showed greater than 99 % 16S rRNA gene sequence similarity to the type strains of several recognized species of the genus Streptomyces, but in the phylogenetic tree based on 16S rRNA gene sequences it formed a distinct phyletic line and demonstrated closest relationships to viomycin-producers (Streptomyces californicus NRRL B-1221(T), Streptomyces floridae MTCC 2534(T) and Streptomyces puniceus NRRL B-2895(T)). However, strain MS1/7(T) could be distinguished from these and other closely related species based on low levels of DNA-DNA relatedness (<44 %) and disparate physiological features, principally amino acid utilization and growth in NaCl. Strain MS1/7(T) is therefore suggested to represent a novel species of the genus Streptomyces, for which the name Streptomyces sundarbansensis sp. nov. is proposed. The type strain is MS1/7(T) ( = MTCC 10621(T) = DSM 42019(T)).

Relationship between volatile odorous substances and production of avermectins byStreptomyces avermitilis

The time course of production of odorous compounds, i.e. geosmin and oxolones, and of avermectins was determined during the cultivation of S. avermitilis in flasks, 1- and 50-L fermentors. The amount of the antibiotics increased with increasing cultivation time up to more than 2 g/L while the concentration of geosmin rose to more than 4 mg/L. Cultivation without reflux condenser resulted in a lower product formation due to the higher stripping of geosmin. A relatively tight correlation was found between the production of geosmin and the production of avermectins. The production of oxolones peaked on cultivation days 3-5, the sum of oxolones being 60 microg/L. Subsequently, the production dropped below a measurable level. This can be explained as being due to the inhibition of oxolone production by geosmin.