New milbemycins from mutant Streptomyces bingchenggensis X-4

Abstract

Streptomyces bingchenggensis produced milbemycins, including a 1 (A 3 ), a 3 (A 4 ), b 13 , b 14 , a 28 , a 29 , a 30 and ST 906, four secomilbemycins A, B, C and D, and two cyclic pentapeptides. [1][2][3][4][5] Milbemycins belong to a 16-membered macrolide antibiotic with an outstanding activity against various kinds of mites. 6 During a screening program for high production of A 3 and A 4 , a mutant S. bingchenggensis X-4 was obtained by UV treated, N-methyl-N¢-nitroso-N-nitroso-guanidine mutation and genetic manipulative techniques. Significant differences of phenotype, such as the morphology of aerial mycelia, and the metabolite HPLC profiles were observed between the wild-type S. bingchenggensis and its mutant strain X-4. In the course of investigating the metabolites of this mutant strain, three new interesting compounds milbemycin b 15 (1), seco-milbemycins E (2) and F (3) were isolated from the fermentation broth of S. bingchenggensis X-4. The structure of compound 1 was similar with milbemycin D, which is a highly selective and potent nematocide and insecticide. 7 So the bioactivity of compound 1 should be further investigated. Compared with the seco-milbemycins isolated previously, 2,3 the hydroxy groups at C-5 were absent in compounds 2 and 3. Furthermore, all the milbemycins 3,8 and avermectins 9,10 obtained from microorganisms contain the hydroxyl at C-5, and the 5-dehydroxyl derivatives of milbemycins and avermectins can only be obtained using the synthetic methods. 11 So seco-milbemycins E and F may have an important role in understanding and perfecting the proposed biosynthesis pathways of milbemycins.The producing strain S. bingchenggensis X-4 was maintained on an 1/2YM slant agar consisting of sucrose 0.4%, skim milk 0.1%, yeast extract (OXOID Basingstoke, Hampshire, UK) 0.2%, malt extract (BD Biosciences, San Jose, CA, USA) 0.5%, agar (BD Biosciences) 2.0% at 28 1C for 12 days. 12 A seed 15-l fermentor (FUS-15 L (A), Shanghai Guoqiang Bioengineering Equipment, Shanghai, China) containing 10 l of seed medium (sucrose 1.0%, polypepton 0.2%, K 2 HPO 4 0.05%, skim milk 0.05%) 12 was inoculated with 0.5 l of broth cultured in flask with seed medium. The flask with seed medium (2-6Â10 7 spores per ml) was cultured for 30 h at 28 1C on a rotary shake at 250 r.p.m.After incubation for 32 h, the seed broth (3 l) in the 15-l fermentor was transferred into the production 50-l fermentor (FUS-50 L (A), Shanghai Guoqiang Bioengineering Equipment) containing 30-l production medium (16.0% sucrose, 2.0% soybean powder, 0.5% yeast extract, 0.5% meat extract, 0.05% K 2 HPO 4 , 0.05% MgSO 4 7H 2 O, 0.005% FeSO 4 7H 2 O and 0.3% CaCO 3 ). 12 The culture temperature was 28 1C and the initial pH was 7.40 sterilized by sparging with steam at 121 1C for 30 min. The dissolved oxygen was maintained above 35% by adjusting the agitation speed. The initial aeration and agitation rate in the 15-l reactor was 1 vvm and 180 r.p.m., whereas those in the 50 l were 0.8 vvm and 150 r.p.m., respectively. In the process of fermenta...

Sbi00515, a Protein of Unknown Function from Streptomyces bingchenggensis, Highlights the Functional Versatility of the Acetoacetate Decarboxylase Scaffold

“…S. bingchenggensis is notable not only for the sheer size of its genome [at ∼12 million bp (10106 genes), it is one of the largest bacterial genomes known] but also for the number of secondary metabolites it produces. These include the antihelminthic milbamycins A3 and A4 that are used extensively to control worms in animals, 10 additional milbemycin analogues, − the polyether antibiotic nanchangmycin, the antitumor agents bingchamide A and B, and at least 23 uncharacterized nonribosomal peptide, polyketide, or terpene biosynthetic clusters . The gene encoding Sbi00515 is near one of the uncharacterized polyketide synthase genes, raising the possibility that Sbi00515 has some role in synthesizing an as-yet-unknown natural product.…”

1,19-seco-Avermectin Analogues from a ΔaveCDE Mutant Streptomyces avermectinius Strain

“…This is the first report of 1,19-seco-AVE analogues. These structures are closely related to seco-milbemycins A–F from S. bingchenggensis − and seco-nemadectin from S. microflavus neau, , all of which share a benzopyrone unit at C1–C8a. These compounds are supposed to be formed by lactonization of the C8a hydroxy (rather than the C19 hydroxy) with the C1 carboxyl .…”

Roblox-based tsunami survival game: A tool to stimulate early childhood disaster preparedness skills

“…The research output is a learning media in the form of a tsunami survival game built with the Roblox engine to help children improve their tsunami disaster preparedness skills. The tsunami survival game media is designed in such a way as to attract children's interest in using game media as a disaster education media [12,13]. This tsunami survival game media is designed with an environment that mimics real-world conditions, including the presence of school buildings, markets, hospitals, beaches, and escape buildings.…”