水生生物的紫外防护剂——类菌胞素氨基酸

类菌胞素氨基酸(mycosporine-like amino acids, MAAs)是一大类以环己烯酮为基本骨架, 与不同类型氨基酸通过缩合作用形成的水溶性物质。它能在真菌、海洋细菌、蓝藻和真核藻类细胞中合成, 并在海生无脊椎动物和鱼类等生物体内积累, 广泛存在于多种水生生物中。它具有紫外光防护、渗透、繁殖调节及发育保护等功能。本文主要介绍有关类菌胞素氨基酸的分布、结构、生物合成和积累以及生理功能的研究进展。     

类菌胞素氨基酸的结构特征、分布、制备技术及生物活性研究进展

类菌胞素氨基酸(mycosporine-like amino acids,MAAs)是一类水生生物次级代谢产物,广泛存在于多种水生生物中。在化学结构上,MAAs是以环己烯酮为基本骨架,与多种类型氨基酸通过缩合作用而形成水溶性活性物质。据报道,类菌胞素氨基酸具有罕见的紫外光防护作用,近年来已倍受重视,成为研究热点。本文主要介绍类菌胞素氨基酸的结构、分布、制备技术、生物活性及其在化妆品领域应用的研究进展。     

多杀菌素生物合成的研究进展北大核心CSCD

多杀菌素是在刺糖多胞菌发酵液中提取的一种大环内酯类生物杀虫剂,它对靶标昆虫具有独特的快速触杀和摄食毒性,兼具化学农药的速效性和生物农药的安全性,具有低残留、快速降解等优点。本文介绍了多杀菌素的生物合成途径和体外合成方法,对随机诱变、代谢工程定向改造等刺糖多孢菌工业菌株育种方法进行了介绍,对多杀菌素在异源宿主中的合成进行了讨论。     

鱼腥草素钠与红霉素抗铜绿假单胞菌生物被膜的协同作用

目的研究鱼腥草素钠与红霉素抗铜绿假单胞菌(Pseudomonas aeruginosa,PA)生物被膜(Biofilm,BF)的协同作用。方法采用微量倍比稀释法测定鱼腥草素钠、红霉素对铜绿假单胞菌最低抑菌浓度(MIC),MTT法测定鱼腥草素钠、红霉素及两药联合抗铜绿假单胞菌的最小抑膜浓度SMIC(SMIC50和SMIC80),光学显微镜及扫描电镜下观测鱼腥草素钠抗铜绿假单胞菌生物被膜的动态过程。结果鱼腥草素钠和红霉素抗铜绿假单胞菌的MIC分别为512 mg/L和256 mg/L。红霉素对铜绿假单胞菌生物被膜SMIC50黏附期为64 mg/L,早期生物被膜阶段为64 mg/L,成熟期生物被膜阶段为128 mg/L,两药联合后铜绿假单胞菌生物被膜SMIC50黏附期为16 mg/L,早期为16 mg/L,成熟期为32 mg/L。红霉素对铜绿假单胞菌生物被膜SMIC80黏附期为128 mg/L,早期生物被膜阶段为128 mg/L,成熟期生物被膜阶段为256mg/L,两药联合后铜绿假单胞菌生物被膜SMIC80黏附期为64 mg/L,早期为64 mg/L,成熟期为128 mg/L。结论鱼腥草素钠联合红霉素抗铜绿假单胞菌生物被膜具有协同作用。     

荧光假单胞菌M18 rpoD克隆及其对抗生素合成的影响

荧光假单胞菌M18对多种植物病原真菌具有显著的抑制作用。荧光假单胞菌(Pseuclomones fluo-rescens)M18能同时合成吩嗪-1-羧酸(PCA)和藤黄绿菌素(P1t)两种抗生素。从M18的基因组中克隆了rpoD基因,其相应的氨基酸序列与荧光假单胞菌CHAO中RpoD蛋白的氨基酸序列完全相同。利用基因重组技术和大肠杆菌-荧光假单胞菌穿梭质粒,pME6032,将rpoD置于强启动子Ptac的控制下,导入M18菌株。发现经重组质粒转化的M18,与对照相比,培养基中PCA和Plt开始累积的时间分别提前4h和8h,积累量提高1倍和6倍.     

荧光假单胞菌M18rpoD克隆及其对抗生素合成的影响

荧光假单胞菌M18对多种植物病原真菌具有显著的抑制作用。荧光假单胞菌(Pseuclomones fluorescens)M18能同时合成吩嗪1羧酸（PCA）和藤黄绿菌素(Plt) 两种抗生素。从M18的基因组中克隆了rpoD基因,其相应的氨基酸序列与荧光假单胞菌CHAO中RpoD蛋白的氨基酸序列完全相同。利用基因重组技术和大肠杆菌荧光假单胞菌穿梭质粒pME6032,将rpoD置于强启动子Ptac的控制下,导入M18菌株。发现经重组质粒转化的M18,与对照相比,培养基中PCA和Plt开始累积的时间分别提前4h和8h,积累量提高1倍和6倍。     

鲍曼不动杆菌和铜绿假单胞菌在低碱性氨基酸培养基中对抗菌药物的敏感性

为了探讨鲍曼不动杆菌和铜绿假单胞菌在低碱性氨基酸培养基中对抗菌药物的敏感性,本研究利用常规培养基和低碱性氨基酸培养基,采用琼脂稀释法检测140株鲍曼不动杆菌和60株铜绿假单胞菌对亚胺培南、帕尼培南和罗美培南的最低抑菌浓度,利用K-B纸片扩散法进行药敏实验并计算敏感率。结果显示,在低碱性培养基中,铜绿假单胞菌和鲍曼不动杆菌对三种药物的最低抑菌浓度(MIC)值显著降低,铜绿假单胞菌在低碱性氨基酸培养基中对帕尼培南的敏感率显著上升,而鲍曼不动杆菌对三种药物的敏感性均显著上升。研究表明,在低碱性氨基酸培养基中,鲍曼不动杆菌和铜绿假单胞菌对帕尼培南、亚胺培南和美罗培南的敏感性有所增强,在临床检验中需考虑由培养基导致的敏感性差异。     

荧光假单胞菌M18的rpoS基因克隆及其功能分析

从荧光假单胞菌 (Pseudomonasfluorescentsp .)M1 8基因组中克隆了RNA聚合酶的稳定期σs 因子编码基因rpoS ,推测其氨基酸序列与铜绿假单胞菌、荧光假单胞菌和恶臭假单胞菌的同源性分别为 99 1 %、87 35 %和87 8%。利用体外定点插入突变和同源重组技术 ,构建了M1 8的rpoS突变株M1 8R- 。对突变株M1 8R- 合成抗生素吩嗪 1 羧酸 (PCA)和藤黄绿菌素 (Plt)的动力学分析结果表明 ,在KB或PPM培养基中 ,突变株合成PCA的能力比野生型分别提高了 2 5或 5 78倍 ,但Plt的积累量不受影响。与野生型相比 ,突变株对碳源饥饿的耐性下降。同时 ,在碳源饥饿条件下对过氧化氢、乙醇和和氯化钠等环境胁迫的交叉保护性减小 ,存活率显著降低     

类产碱假单胞菌杀虫物质的分离纯化和鉴定

类产碱假单胞菌是一株昆虫病原菌,该菌对草地蝗虫、竹蝗等具有良好的致死作用,经鉴定,该菌对蝗虫具有毒杀作用的物质为其代谢分泌到胞外的一种蛋白质。类产碱假单胞菌培养物经硫酸按沉淀,SephadexG-100凝胶过滤及DEAE-SephadexA-50阴离子交换柱层析,纯化获得的杀虫蛋白只含一种亚基,分子量25100,等电点5．16,含17种氨基酸,其中谷氨酸含量最高,胱氨酸含量最低,最大吸收峰为278．3nm。     

靶向破坏铜绿假单胞菌生物被膜的定向蛋白投放技术

【目的】随着合成生物学的发展,通过在细菌体内设计合成复杂、多功能的基因线路进行靶向治疗已经取得巨大进展。虽然这种使用细菌作为治疗传递系统,选择性地在体内释放有效治疗成分的方式具有极大优势,但是如何使细菌在代谢负荷增加较低的情况下有效地分泌功能蛋白并发挥作用依旧是一个难题。【方法】针对这一难题,本研究提供了一种新的策略,即以细菌中广泛存在的蛋白类杀菌素和丝状噬菌体等相关编码基因作为生物模块,通过对铜绿假单胞菌的这些内源生物模块的重新编排和组装,构建了一种能在特定条件下裂解并投放功能蛋白的工程菌。为了评价工程菌中构建的生物模块能否工作,本研究选择胞外多糖水解酶PelA和PslG作为工程菌投放的功能蛋白,以此构建了工程菌PAO1102。通过对铜绿假单胞菌生物被膜的破坏实验、抑制形成实验以及抗生素耐药性实验,检验PAO1102对铜绿假单胞菌生物被膜的破坏和预防效果。【结果】与对照组相比,工程菌PAO1102的处理可以显著破坏已形成的生物被膜并抑制生物被膜的形成,同时还可显著增强生物被膜中的细菌对妥布霉素的敏感性,且这些功能主要通过外界Pf4丝状噬菌体侵染并使工程菌裂解而释放功能蛋白这一途径实现的。【结论】本研究所构建的工程菌可以作为一种微生物工具,用于靶向破坏铜绿假单胞菌生物被膜。在后续的研究中可根据不同的需求,在工程菌中表达不同的功能基因并实现功能蛋白的定向投放,从而执行不同的生物学功能。     

Chemical Composition during Maturing and Spawning of the Sponge Dysidea herbacea (Porifera: Demospongiae)

Mycosporine-like amino acids (MAAs) have been implicated in many biochemical processes in marine organisms, but the major emphasis has been directed to their role as UV protectant compounds. The quantitation of MAAs, mycosporine-glu-gly, mycosporine-gly, usujirene and palythene in the sponge Dysidea herbacea [34] suggests that whereas some mycosporine amino acids may serve in this capacity, others are intrinsically involved in the reproductive process. The role of other compounds, such as homarine, gadusol and arachidonic acid, in reproduction of this sponge is also discussed.     

Production of porphyra-334 in transgenic lines of Nannochloropsis salina by the expression of mycosporine-like amino acid biosynthetic genes of P. yezoensis

Journal of Applied Phycology - Mycosporine-like amino acids (MAAs) are small secondary metabolites produced by some marine species. These compounds absorb ultraviolet (UV) light, typically between...     

Mycosporines and mycosporine-like amino acids: UV protectants or multipurpose secondary metabolites?

Mycosporines and mycosporine-like amino acids (MAAs) are low-molecular-weight water-soluble molecules absorbing UV radiation in the wavelength range 310-365 nm. They are accumulated by a wide range of microorganisms, prokaryotic (cyanobacteria) as well as eukaryotic (microalgae, yeasts, and fungi), and a variety of marine macroalgae, corals, and other marine life forms. The role that MAAs play as sunscreen compounds to protect against damage by harmful levels of UV radiation is well established. However, evidence is accumulating that MAAs may have additional functions: they may serve as antioxidant molecules scavenging toxic oxygen radicals, they can be accumulated as compatible solutes following salt stress, their formation is induced by desiccation or by thermal stress in certain organisms, they have been suggested to function as an accessory light-harvesting pigment in photosynthesis or as an intracellular nitrogen reservoir, and they are involved in fungal reproduction. Here, the evidence for these additional roles of MAAs as 'multipurpose' secondary metabolites is reviewed, with special emphasis on their functions in the microbial world.     

Chemical profiling of mycosporine‐like amino acids in twenty‐three red algal species

Rhodophyta produce a variety of chemically different mycosporine‐like amino acids (MAAs), compounds that are known as some of the strongest ultraviolet (UV) absorbing molecules in nature. Accordingly, they primarily act as photoprotectants against harmful levels of solar ultraviolet radiation in the UV‐A and UV‐B range. In order to get a deeper understanding of the chemical diversity of MAAs in red algae, pure standards of eleven mycosporine‐like amino acids were isolated from three different species (Agarophyton chilense, Pyropia plicata and Champia novae‐zelandiae) using various chromatographic methods. Their structures were confirmed by nuclear magnetic resonance and mass spectrometry. Four out of the eleven MAAs are reported for the first time in algae. In addition, a new high‐performance liquid chromatography method was developed for the separation of all isolated MAAs and successfully applied for the analysis of twenty‐three red algal species of marine origin. All of them contained MAAs, the most abundant compounds were shinorine, palythine, asterina‐330 and porphyra‐334. For some samples, the direct assignment of MAAs based on their UV spectra was not possible; therefore, the target analytes were enriched by a simple concentration step, followed by liquid chromatography‐mass spectrometry analysis of the extracts. This approach enabled a deeper insight into the MAA pattern of red algae, indicating that not only the four dominant ones are synthesized but also many others, which were often described as unknown compounds in previous studies.     

Natural microbial UV radiation filters--mycosporine-like amino acids

Ozone depletion by anthropogenic gases has increased the atmospheric transmission of solar ultraviolet-B radiation (UV-B, 280-315 nm). There is a logical link between the natural defenses of terrestrial and marine organisms against UV radiation and the prevention of UV-induced damage to human skin. UV light degrades organic molecules such as proteins and nucleic acids, giving rise to structural changes that directly affect their biological function. These compounds offer the potential for development of novel UV blockers for human use. The biological role of mycosporine-like amino acids (MAAs) and scytonemin as a defense against solar radiation in organisms, together with their structure, synthesis, distribution, regulation and effectiveness, are reviewed in this article. This review points to the role of MAAs as a natural defense against UV radiation.     

Mycosporine-like amino acids from coral dinoflagellates

Coral reefs are one of the most important marine ecosystems, providing habitat for approximately a quarter of all marine organisms. Within the foundation of this ecosystem, reef-building corals form mutualistic symbioses with unicellular photosynthetic dinoflagellates of the genus Symbiodinium. Exposure to UV radiation (UVR) (280 to 400 nm) especially when combined with thermal stress has been recognized as an important abiotic factor leading to the loss of algal symbionts from coral tissue and/or a reduction in their pigment concentration and coral bleaching. UVR may damage biological macromolecules, increase the level of mutagenesis in cells, and destabilize the symbiosis between the coral host and their dinoflagellate symbionts. In nature, corals and other marine organisms are protected from harmful UVR through several important photoprotective mechanisms that include the synthesis of UV-absorbing compounds such as mycosporine-like amino acids (MAAs). MAAs are small (<400-Da), colorless, water-soluble compounds made of a cyclohexenone or cyclohexenimine chromophore that is bound to an amino acid residue or its imino alcohol. These secondary metabolites are natural biological sunscreens characterized by a maximum absorbance in the UVA and UVB ranges of 310 to 362 nm. In addition to their photoprotective role, MAAs act as antioxidants scavenging reactive oxygen species (ROS) and suppressing singlet oxygen-induced damage. It has been proposed that MAAs are synthesized during the first part of the shikimate pathway, and recently, it has been suggested that they are synthesized in the pentose phosphate pathway. The shikimate pathway is not found in animals, but in plants and microbes, it connects the metabolism of carbohydrates to the biosynthesis of aromatic compounds. However, both the complete enzymatic pathway of MAA synthesis and the extent of their regulation by environmental conditions are not known. This minireview discusses the current knowledge of MAA synthesis, illustrates the diversity of MAA functions, and opens new perspectives for future applications of MAAs in biotechnology.     

Widespread occurrence of mycosporine-like amino acid compounds in scleractinians from French Polynesia

 A survey of 23 species of scleractinians, belonging to seven families and 8 genera, collected from two different areas in French Polynesia, showed that all specimens possessed between four and seven UV-absorbing compounds, identified as mycosporine-like amino acids (MAAs). In all, 11 different MAAs molecules were found, of which two were previously unknown. Palythine and mycosporine-glycine were the most abundant MAAs in the corals. With few exceptions, most specimens of each species possessed the same pattern of MAAs. Similarly, species from the same genus also had very similar qualitative composition of MAAs, although quantities of individuals MAAs varied from specimen to specimen. This suggests that MAAs are ancient and evolutionarily well conserved. Accepted: 22 October 1996     

ULTRAVIOLET SUNSCREENS IN GYMNODINIUM SANGUINEUM (DINOPHYCEAE): MYCOSPORINE-LIKE AMINO ACIDS PROTECT AGAINST INHIBITION OF PHOTOSYNTHESIS

Marine phytoplankton are sensitive to inhibition of photosynthesis by solar ultraviolet (UV) radiation, although sensitivity varies, depending on the growth environment. A mechanism suggested to increase resistance to UV inhibition is the accumulation of UV-absorbing compounds, such as the mycosporine-like amino acids (MAAs) found in many marine organisms. However, the effectiveness of these compounds as direct optical screens in microorganisms has remained unclear. The red-tide dinoflagellate Gymnodinium sanguineum Hirasaka accumulates about 14-fold more MAAs (per unit of chlorophyll) in high (76 W·m⁻²) than in low (15 W·m⁻²) growth irradiance. Biological weighting functions were estimated for UV inhibition of photosynthesis and showed that the high-light-grown cultures have lower sensitivity to UV radiation at wavelengths strongly absorbed by the MAAs. The time course of photosynthesis during exposure to UV radiation was measured using pulsed amplitude modulated (PAM) fluorometry and displayed a steady-state level after 15 min of exposure, indicating active repair of damage to the photosynthetic apparatus. Repair was blocked in the presence of the antibiotic streptomycin, yet high-light G. sanguineum remained less sensitive to UV radiation than did low-light cultures. These experiments show that MAAs act as spectrally specific UV sunscreens in phytoplankton.