Discovery of a new nosiheptide-producing strain and its fermentation optimization for nosiheptide production / 中国药科大学学报

@#Nosiheptide is a typical thiopeptide antibiotic displaying potent activity toward various drug-resistant strains of Gram-positive pathogens.Although nosiheptide lacks in vivo activity, and good water-solubility with a series of uncontrollable analogues, which may limit its clinical application, glycosylated analogues may overcome problem of low activity and may improve its druggability.In search of novel glycosylated nosiheptide producers, we applied a genome mining strategy that identified Actinoalloteichus sp.AHMU CJ021 that contains all genes required.However, despite the presence of a predicted glycosyltransferase, glycosylated derivatives of nosiheptide were not detected, after following one strain many compounds (OSMAC) strategy and heterologous expression of a regulatory protein NocP.Nevertheless, nosiheptide produced by this strain was remarkably pure, and further experiments were conducted to improve its production by optimization of the culture medium.Under optimal conditions, 58.73 mg/L nosiheptide was produced, representing an almost 6-fold improvement compared to the original fermentation medium.Therefore, we consider Actinoalloteichus sp.AHMU CJ021 a suitable potential candidate for industrial production of nosiheptide, which provides the basis for solving the problem of nosiheptide structural analogues.

Genome sequencing of Streptomyces aureofaciens DM-1 and analysis of 6-demethylchlortetracycline biosynthesis gene cluster / 生物工程学报

Streptomyces aureofaciens DM-1 is a high-yielding 6-demethylchlortetracycline producer. The genome sequencing of DM-1 reveals a linear chromosome containing 6 824 334 bps nucleotides with GC content of 72.6%. In this genome, a total of 6 431 open reading frames were predicted by using glimmer 3.02, Genemark and Z-Curve softwares. Twenty-eight secondary metabolite biosynthetic gene clusters were uncovered by using AntiSMASH gene prediction software, including the complete 6-demethylchlortetracycline biosynthetic gene cluster. A frame-shift mutation in methyltransferase coding region was detected, which may result in the demethylation of chlortetracycline. The complete genome sequence of S. aureofaciens DM-1 provides basic information for functional genomics studies and selection of high-yielding strains for 6-demethylchlortetracycline.

Application of TAR cloning in microbial secondary metabolites / 中国药科大学学报

@#Microbial secondary metabolites have been a major source for drug discovery and development due to their structural novelty and diversity. Microbial secondary metabolites, typically encoded by specific biosynthetic gene cluster(BGC), are non-essential for the growth and propagation of the microbes. Despite the abundant existence of microbes, the majority of them are unculturable under laboratory conditions. Moreover, given that most of the BGCs from culturable microbes are silent, the discovery of novel microbial secondary metabolites has been hampered. Recently, the heterologous expression of BGCs has become an attractive approach to discover various microbial secondary metabolites, among which TAR-based heterologous expression is one of the important tools. This review summarized the principle of TAR, the applications and the advanced strategies of TAR-based methods for heterologous expression of secondary metabolites, which may help the advancements of drug discovery and development from microbial sources.

Comparative analysis of rapamycin biosynthesis clusters between Actinoplanes sp. N902-109 and Streptomyces hygroscopicus ATCC29253 / 中国天然药物

The present study was designed to identify the difference between two rapamycin biosynthetic gene clusters from Streptomyces hygroscopicus ATCC29253 and Actinoplanes sp. N902-109 by comparing the sequence and organization of the gene clusters. The biosynthetic gene cluster for rapamycin in Streptomyces hygroscopicus ATCC29253 was reported in 1995. The second rapamycin producer, Actinoplanes sp. N902-109, which was isolated in 1995, could produce more rapamycin than Streptomyces hygroscopicus ATCC29253. The genomic map of Actinoplanes sp. N902-109 has been elucidated in our laboratory. Two gene clusters were compared using the online software anti-SMASH, Glimmer 3.02 and Subsystem Technology (RAST). Comparative analysis revealed that the organization of the multifunctional polyketide synthases (PKS) genes: RapA, RapB, RapC, and NRPS-like RapP were identical in the two clusters. The genes responsible for precursor synthesis and macrolactone modification flanked the PKS core region in N902-109, while the homologs of those genes located downstream of the PKS core region in ATCC29253. Besides, no homolog of the gene encoding a putative type II thioesterase that may serve as a PKS "editing" enzyme accounted for over-production of rapamycin in N902-109, was found in ATCC29253. Furthermore, no homologs of genes rapQ (encoding a methyltransferase) and rapG in N902-109 were found in ATCC29253, however, an extra rapM gene encoding methyltransferase was discovered in ATCC29253. Two rapamycin biosynthetic gene clusters displayed overall high homology as well as some differences in gene organization and functions.