understanding nikkomycin biosynthesis in …
To increase the yields of nikkomycins, an additional copy of nikkomycin biosynthetic gene cluster (35 kb) was introduced into nikkomycin producing strain, S. ansochromogenes 7100. The gene cluster was first reassembled into an integrative plasmid by Red/ET technology combining with classic cloning methods and then the resulting plasmid(pNIK)was introduced into S. ansochromogenes by conjugal transfer. Introduction of pNIK led to enhanced production of nikkomycins (880 mg L-1, 4 -fold nikkomycin X and 210 mg L-1, 1.8-fold nikkomycin Z) in the resulting exconjugants comparing with the parent strain (220 mg L-1 nikkomycin X and 120 mg L-1 nikkomycin Z). The exconjugants are genetically stable in the absence of antibiotic resistance selection pressure.
Reassembling of the nikkomycin biosynthetic gene cluster by Red/ET
A high nikkomycins producing strain (1100 mg L-1 nikkomycins) was obtained by introduction of an extra nikkomycin biosynthetic gene cluster into the genome of S. ansochromogenes. The strategies presented here could be applicable to other bacteria to improve the yields of secondary metabolites.
A nikkomycin Z producing strain (sanPDM) was constructed by blocking the imidazolone biosynthetic pathway of nikkomycin X via genetic manipulation and yielded 300 mg/L nikkomycin Z and abolished the nikkomycin X production. To further increase the yield of nikkomycin Z, the effects of different precursors on its production were investigated. Precursors of nucleoside moiety (uracil or uridine) had a stimulatory effect on nikkomycin Z production while precursors of peptidyl moiety (L-lysine and L-glutamate) had no effect. sanPDM produced the maximum yields of nikkomycin Z (800 mg/L) in the presence of uracil at the concentration of 2 g/L and it was approximately 2.6-fold higher than that of the parent strain.
bond formation in nikkomycin biosynthesis.
In this paper, a strain which produced high-level of nikkomyicns obtained by traditional strain improvement was chosen as the parent strain for genetic manipulation. A nikkomycin Z selectively producing strain was generated by blocking the imidazolone biosynthetic pathway of nikkomycin X. The subsequent uracil feeding further enhanced the yield of nikkomycin Z.
• Biosynthesis of nucleoside ..
To obtain an ideal strain only producing nikkomycin Z, the disruption of sanP in S. ansochromogenes TH322 was performed (Fig. ). sanP is an homologue of nikP2 of S. tendae (sharing 95% identity), which is vital for the biosynthesis of imidazolone that is an unique part of nikkomycin X . The resulting sanP disruption mutant (sanPDM) was passed through five generations in the absence of antibiotic pressure. The progeny still conferred kanamycin resistance, indicating the resulting sanPDM was genetically stable.
of Nikkomycin X from Histidine in Streptomyces tendae ..
N2 - Polyoxins and nikkomycins are a class of naturally occurring peptidyl nucleoside antibiotics that show promise as potential antifungal agents due to their potent ability to inhibit chitin synthase, an enzyme responsible for fungal cell wall biosynthesis. Whole cell assays and in vivo studies have shown that these natural products have poor cellular uptake and are metabolically unstable, and there has been a concerted effort to improve their pharmokinetic properties by synthesizing analogs. These have either been designed as natural substrate analogs, transition state mimetics or mechanistic inhibitors. Recent synthetic efforts and the results of their biological studies are briefly described in this review, and the current trends in the design and construction of polyoxin and nikkomycin analogs are discussed.
Improvement of gougerotin and nikkomycin production …
In S. ansochromogenes, sanP is located in one of the operons . To exclude the potential polar effect of sanP disruption on the loss of nikkomycin X, the complementary plasmid pIM229::sanP constructed with wild type sanP under the control of the ermE* promoter was introduced into the sanPDM. The introduction of pIM229::sanP into sanPDM restored nikkomycin X production. HPLC analysis and bioassay showed that the amounts of nikkomycins produced by the complemented strain were almost the same as those produced by the parent strain (Fig. ). The disruption and complementation experiments suggested that sanP was a key determinant in nikkomycin X biosynthesis and disruption of sanP did not affect the production of nikkomycin Z.