基因组挖掘默诺霉素生物合成基因簇的比较分析

通过对NCBI数据库的检索,使用次级代谢基因挖掘的方法对整个基因组数据进行扫描,发现含有潜在的默诺霉素家族磷酸糖脂类抗生素合成途径基因簇的6株链霉菌:Streptomyces ghanaensis、Streptomyces bambergiensis、 Streptomyces prasinus、 Streptomyces lincolnensis、 Streptomyces. sp. SAT1和Streptomyces clavuligerus。将搜寻获取的候选基因簇与S. ghanaensis中的默诺霉素合成相关基因簇进行比较基因组学分析,从共线性比对、合成基因的进化水平和同源性比对结果的分析,说明默诺霉素合成基因簇存在两种不同的进化来源与途径。其中5株链霉菌的合成基因簇位于染色体的两臂区,该区域常发生染色体插入或缺失的水平转移。通过对移动元件的基因岛序列的预测,发现默诺霉素合成基因簇是由20 kb大小的基因组岛实现了种间水平转移。基因组岛的插入是链霉菌获得新性状的重要途径,可以阐述基因簇在种间转移的途径和进化方向,以生物信息学基因组分析的角度为高产菌株的构建提供数据支持和改造。     

以生物合成为基础的代谢工程和组合生物合成

代谢工程和组合生物合成在筛选和发展新型药物方面日益成为生物、化学和医药界关注的重点。基于聚酮和聚肽类天然产物的独特化学结构和良好生物活性,研究它们的生物合成机制,将为合理化遗传修饰生物合成途径获得结构类似物提供遗传和生物化学的基础,实现利用现代生物学和化学的技术手段在微生物体内进行药物开发的目的。     

达托霉素生物合成研究进展

达托霉素是由玫瑰孢链霉菌(Streptomyces roseosporus)生产的一种环脂肽类抗生素, 具有强大的抗革兰氏阳性致病细菌的作用, 是继“抗生素最后一道防线”万古霉素后的新型抗生素。本文主要对达托霉素的结构、作用机制、合成基因簇及合成机制等当前的研究成果进行综述, 并且总结了利用组合生物学对达托霉素进行结构改造的策略, 以此来研究结构与活性之间的关系, 并寻找更广谱高效的抗生素。最后, 本文总结了提高达托霉素产量的策略, 为工业上降低达托霉素生产成本提供理论参考。     

羊肚菌多糖提取分离及生物活性研究进展*

羊肚菌(Morchella spp.)是一种珍稀食药用真菌,从羊肚菌中提取的多糖在抗癌、抗氧化、降血糖、降血脂及免疫调节等方面具有良好的生物活性,在食品、药品和保健品开发方面具有广阔的应用前景。羊肚菌多糖的有效提取是对其进行结构解析和生物活性研究的基础,不同的提取方式对羊肚菌多糖的结构和生物活性具有一定影响。羊肚菌多糖的结构特性如分子量、单糖组成、一级结构等,对其生物活性具有很大影响,因此研究羊肚菌多糖的结构对揭示其生物活性及作用机制具有重要意义。针对羊肚菌多糖进行综述,总结羊肚菌多糖提取分离、结构解析及生物活性的研究进展,分析羊肚菌多糖生物活性的作用机制,并对今后研究方向提出展望,以期为羊肚菌多糖的研究与开发提供理论基础。     

植物细胞壁形成机制的新进展

细胞壁是植物细胞重要的特征结构,也是地球上最大的可再生碳水化合物资源库.随着近20多年研究技术的发展和多学科交叉手段的应用,植物细胞壁的形成机理得到了很大程度的揭示,勾画出了细胞壁合成、物质转运、形成调控、沉积重构等基本的代谢框架,涉及从胞内到胞外一系列的合成、转运和调控途径.本文概述了近年来细胞壁形成机理研究的热点问题和最新进展,包括对细胞壁结构和成分的新认识,纤维素合成场所(细胞质膜)和非纤维素多糖合成场所(高尔基体)中关键蛋白的挖掘及作用机制的新发现,细胞壁物质膜泡转运与细胞骨架的关系,以及细胞壁形成信号与转录调控网络的新进展.这些发现不仅使人们对细胞壁的合成机理有了更深入的认识,也为细胞壁经济价值的开发与利用奠定了重要的理论基础.同时本文还对该领域未来可能的热点和研究方向进行了展望.     

哌珀霉素类抗菌肽:一类特殊的肽类抗生素

Peptaibol(建议译名：哌珀霉素)是一类从土壤真菌中分离到的具有抑制细菌和真菌作用的抗菌肽的总称。独特的结构特点、多样的生物学特性和特殊的作用机制,使对peptaibol的研究不断深入。该介绍peptaibol的结构特点、生物学特性和作用机制等。     

第二十一讲 高等植物细胞壁的生物合成

前言植物细胞壁的生物学意义及其对人类经济生活的重要性,已为人们所熟知。根据Hess(1928)估计,每年全世界约生产10~(11)吨纤维素,为世界上最丰富的高分子化合物。由于近代物理学、化学、生化等新技术的发展,植物细胞壁的生物合成向题,引起分子生物学家的极大兴趣。本文介绍有关高等植物细胞壁生物合成研究的概况。细胞壁是植物界细胞结构的重要组成成份,它能稳定细胞的形态,支持植物体的固着生活;而且有时还复盖角质、蜡质和木栓质     

鞘糖脂的人工合成体系研究进展

鞘糖脂(glycosphingolipids,GSLs)是真核生物细胞膜的重要组成部分,广泛参与细胞信号传导、免疫、增殖及凋亡等各项生理活动。鞘糖脂类具有作为药物、治疗靶标及潜在诊断标记的潜力,并且与多种疾病的发病机制及相关药物开发密切相关。目前,鞘糖脂类药物的大量制备主要依赖从动物脑组织中提取,存在成本较高、来源有限且有受疯牛病等人畜共患病污染的潜在危险。因此,对鞘糖脂的人工生物合成研究成为学术界的热点。本文中,笔者主要阐述鞘糖脂的化学酶法合成和人工细胞工厂构建方面的研究进展。     

达托霉素耐药分子机制研究进展

环脂肽抗生素达托霉素抗菌活性强,致病菌不容易产生耐药性,已成为治疗革兰氏阳性菌特别是耐药菌感染的一线药物。但由于广泛使用,仍然出现了达托霉素耐药菌。细胞膜磷脂代谢和细胞壁结构动态与致病菌达托霉素耐药密切相关。文中综述了达托霉素作用机制和耐药机制,以期对药物研发和临床用药有所裨益。     

雌马酚的生物活性和临床应用

雌马酚是大豆异黄酮(SI)的主要组分之一——大豆素(Dai)的代谢产物。雌马酚较其原型具有更为有效的生物学作用,虽其作用及机制还存在争议,但很多研究表明雌马酚的生物学作用以及在适用人群显然都优于SI,并受到普遍关注。研究和开发雌马酚的生物活性,在多种常见慢性病的预防与控制中有重要的理论和实际意义。     

MoeH5: a natural glycorandomizer from the moenomycin biosynthetic pathway

The biosynthesis of the phosphoglycolipid antibiotic moenomycin A attracts the attention of researchers hoping to develop new moenomycin‐based antibiotics against multidrug resistant Gram‐positive infections. There is detailed understanding of most steps of this biosynthetic pathway in Streptomyces ghanaensis (ATCC14672), except for the ultimate stage, where a single pentasaccharide intermediate is converted into a set of unusually modified final products. Here we report that only one gene, moeH5, encoding a homologue of the glutamine amidotransferase (GAT) enzyme superfamily, is responsible for the observed diversity of terminally decorated moenomycins. Genetic and biochemical evidence support the idea that MoeH5 is a novel member of the GAT superfamily, whose homologues are involved in the synthesis of various secondary metabolites as well as K and O antigens of bacterial lipopolysaccharide. Our results provide insights into the mechanism of MoeH5 and its counterparts, and give us a new tool for the diversification of phosphoglycolipid antibiotics.     

Genes for biosynthesis of butenolide-like signalling molecules in Streptomyces ghanaensis,their role in moenomycin production

Moenomycins (Mm)—phosphoglycolipid compounds produced by Streptomyces ghanaensis ATCC14672—are considered a promising model for development of novel-class of antibiotics. In this regard it is important to generate Mm overproducing strains which would be a basis for economically justified production of this antibiotic. In this work a set of genes for synthesis and reception of low-molecular weight signaling molecules (LSM) in ATCC14672 were described and their significance for Mm production was studied. The ATCC14672 genome carries structural and regulatory genes for production of LSMs of avenolide and γ-butyrolactone families. Additional copies of LSM biosynthetic genes ssfg_07848 and ssfg_07725 did not alter the Mm production level. ATCC14672 LSMs are not capable of restoring the sporulation of butyrolactone-nonproducing mutant of S. griseus. Likewise, while the heterologous host S. lividans 1326 produced Mm, its mutant M707 (deficient in the butyrolactone synthase gene scbA) did not. Thus, while the natural level of LSMs production by ATCC14672 does not limit Mm synthesis, the former is essential for the synthesis of moenomycins.     

化学品生物合成专刊序言

以酶及微生物细胞催化剂结合工程学方法将廉价、废弃原料进行高效生物转化可实现化学品的可持续生产。近年来,合成生物学、系统生物学及酶工程等技术的快速发展大大推动了化学品的可持续生物制造,既实现了多种新型化学品的生物合成,又显著提高化学品的生物合成效率。为展示化学品生物合成的最新进展并促进绿色生物制造的发展,《生物工程学报》特组织出版化学品生物合成专刊,从酶催化与生物合成机制、微生物细胞合成、一碳生物炼制以及关键核心技术等方面,介绍化学品生物合成的最新前沿、挑战以及潜在解决方案。     

Genetic factors that influence moenomycin production in streptomycetes

Moenomycin, a natural phosphoglycolipid product that has a long history of use in animal nutrition, is currently considered an attractive starting point for the development of novel antibiotics. We recently reconstituted the biosynthesis of this natural product in a heterologous host, Streptomyces lividans TK24, but production levels were too low to be useful. We have examined several other streptomycetes strains as hosts and have also explored the overexpression of two pleiotropic regulatory genes, afsS and relA, on moenomycin production. A moenomycin-resistant derivative of S. albus J1074 was found to give the highest titers of moenomycin, and production was improved by overexpressing relA. Partial duplication of the moe cluster 1 in S. ghanaensis also increased average moenomycin production. The results reported here suggest that rational manipulation of global regulators combined with increased moe gene dosage could be a useful technique for improvement of moenomycin biosynthesis.     

Streptomyces ghanaensis pleiotropic regulatory gene wblA(gh) influences morphogenesis and moenomycin production

The wblA _gh gene, encoding a homologue of the WhiB-family of proteins, was identified in the sequenced genome of moenomycin producer Streptomyces ghanaensis. Deletion of the gene blocked aerial mycelium sporulation and caused a 230% increase in moenomycins production. S. ghanaensis overexpressing SSFG-01620: a homologue of extracellular protease inhibitor SCO0762, whose expression in Streptomyces coelicolor is down-regulated by wblA: showed deficiencies in sporulation similar to that of wblA _gh knockout strain. The wblA _gh gene of S. ghanaensis appears to play a negative role in the control of moenomycin biosynthesis and is essential for sporulation.     

Biosynthesis and beneficial effects of microbial gibberellins on crops for sustainable agriculture

Soil microbes promote plant growth through several mechanisms such as secretion of chemical compounds including plant growth hormones. Among the phytohormones, auxins, ethylene, cytokinins, abscisic acid and gibberellins are the best understood compounds. Gibberellins were first isolated in 1935 from the fungus Gibberella fujikuroi and are synthesized by several soil microbes. The effect of gibberellins on plant growth and development has been studied, as has the biosynthesis pathways, enzymes, genes and their regulation. This review revisits the history of gibberellin research highlighting microbial gibberellins and their effects on plant health with an emphasis on the early discoveries and current advances that can find vital applications in agricultural practices.     

链霉菌底盘细胞的开发现状及其应用

天然产物及其衍生物在现代医疗中扮演着举足轻重的角色,其生物活性多样性以及化学结构的丰富性是新药研发的源泉和动力。利用纯化学方法合成天然产物在技术和成本上有很大的困难,加上许多天然产物的原始产生菌具有培养条件苛刻、产量低下等缺点,而且大量基因簇在原始菌株中是沉默的,这使得利用合成生物学思想来指导天然产物生物合成基因簇的异源表达具有重大意义。作为抗生素、抗肿瘤活性物质、免疫抑制剂等次级代谢产物主要来源的放线菌一直是研究者们关注的焦点,特别是随着基因测序技术的飞速发展,人们发现链霉菌基因组中包含着极为丰富的天然产物生物合成基因簇资源。这意味着开发链霉菌底盘细胞作为异源表达宿主有其得天独厚的优势。本综述从底盘细胞开发的意义入手,重点阐述链霉菌底盘细胞构建的策略及现状,随后通过实例阐述了各种底盘链霉菌的实际应用。     

Identification and characterization of Streptomyces ghanaensis ATCC14672 integration sites for three actinophage-based plasmids

Streptomyces ghanaensis produces the antibiotic moenomycin A, which is the only known direct inhibitor of bacterial peptidoglycan glycosyltransferases (transglycosylases). Recent progress in understanding moenomycin biosynthesis opens the door to the generation of novel moenomycins via biocombinatorial approaches. To realize the promise of such an approach, one needs better knowledge of the S. ghanaensis genome and diverse genetic tools for stable expression of recombinant constructs in this strain. In this respect, we report the intergeneric Escherichia coli–S. ghanaensis conjugal transfer of plasmids pRT801 and pSOK804 based on the actinophage BT1 and VWB integrase systems, respectively. The attB sites for these two plasmids and for pSET152 were characterized. In particular, sequencing revealed that a putative Arg-tRNA gene serves as an integration site for both phage VWB and pSAM2-like actinomycete integrative and conjugative element recently suggested to be widespread and functional in actinomycetes. The stability of the studied plasmids and their neutrality with respect to antibiotic production warrant their use for manipulations of S. ghanaensis genome.     

Incorporation of [14C]glucose from UDP[14C]glucose into a phosphoglycolipid by cell-free particulate systems of a moderately halophilic gram-negative bacterium, Pseudomonas halosaccharolytica ATCC 29423.

A glucosyl group from uridine diphosphate [U-14C]glucose is incorporated into a phosphoglycolipid, probably a glucosylphosphatidylglycerol, by a disrupted membrane enzyme preparation from a gram-negative, moderately halophilic bacterium, Pseudomonas halosaccharolytica ATCC 29423. The conversion of [14C]phosphatidylglycerol into phosphoglycolipid by the particulate preparation was also enhanced in the presence of non-labelled UDP-glucose. A chemical degradation study of labelled phosphoglycolipid showed the bulk of the radioactivity from UDP[U-14C]glucose to be associated with the glucose moiety, which also appeared to be attached to the hydroxyl group of a second glycerol.