真菌几丁质合酶的研究进展

真菌细胞壁几丁质的合成是一个复杂的过程, 其关键酶为几丁质合酶(CS)。近年来, 丝状真菌中的CS研究有了大的突破, 与酿酒酵母中只有3种CS不同, 丝状真菌中存在7种类别的CS。大部分临床和农业中重要的病原真菌都是丝状真菌, 文中对真菌中7种类别CS的结构和功能作了概述, 重点讨论了丝状真菌中重要的CS类别, 并介绍了CS作为抗真菌药物有效靶标的研究现状, 旨在为研究真菌CS及其抑制剂提供参考。     

真菌几丁质合酶的研究进展

真菌细胞壁几丁质的合成是一个复杂的过程,其关键酶为几丁质合酶(CS).近年来,丝状真菌中的CS研究有了大的突破,与酿酒酵母中只有3种CS不同,丝状真菌中存在7种类别的CS.大部分临床和农业中重要的病原真菌都是丝状真菌,文中对真菌中7种类别CS的结构和功能作了概述,重点讨论了丝状真菌中重要的CS类别,并介绍了CS作为抗真菌药物有效靶标的研究现状,旨在为研究真菌CS及其抑制剂提供参考.     

过氧化氢酶在病原性真菌中的相关研究进展

过氧化氢酶普遍存在于原核和真核生物,具有抗氧化作用。这种作用有其有利的方面,即保护细胞免受氧自由基等氧化物的损害,抑制细胞受氧化因素刺激诱导的凋亡。同样,有其不利的方面,即保护病原微生物(包括真菌)不受宿主氧化系统的破坏。抗氧化作用作为病原性真菌的一种可能致病机制,国外已经有不少相关的报道,但是目前国内对这方面的研究较少,本文就过氧化氢酶在病原性真菌中的相关研究进展做一综述。     

细菌几丁质酶研究进展

真菌病害是影响作物产量的重要原因 ,而几丁质酶能有效抑制其生长、水解其细胞壁。对研究较多的细菌几丁质酶及几丁质酶基因的分子生物学研究进展进行了综述 ,并对细菌几丁质酶基因利用存在的问题进行了探讨。     

植物几丁质酶的研究进展

自 1 92 1年Ｆｏｌｐｍｅｒｓ首次从细菌和放线菌中证实水溶性几丁质酶存在以来 ,研究者又相继在多种微生物、植物、动物中分离到几丁质酶。在高等植物中 ,几丁质酶分布于草本植物和木本植物或单子叶植物和双子叶植物 ,主要存在于植物的根、茎、叶、花、果实、种子及胚等部位 ,种子、花器、根中的几丁质酶含量一般高于其它器官[1] 。现以在玉米、水稻、小麦、大麦、棉花、油菜、甜橙等 70多种栽培植物和野生植物中检测到几丁质酶活性[2 ] 。1　几丁质酶的特性及分类定位1 1　几丁质酶的一般特性几丁质酶是一种糖苷酶 ,以几丁质 [(1 ,4) - 2…     

几丁质酶及其研究进展

本文从几丁质酶的分布、发育调节、可诱导性、分子生物学及抗病基因工程等方面近年来的进展进行了综合论述,并对其进一步的应用提出展望。     

植物几丁质酶及其在抗真菌病害中的应用

植物几丁质酶的研究是抗真菌基因工程的热点之一。几丁质酶能够水解真菌细胞壁的主要成分几丁质,在植物抗真菌病害反应中发挥重要的作用。介绍了几丁质酶的基本生物学特性、基因的诱导表达,并对植物几丁质酶基因在抗真菌病害基因工程中的应用进行了阐述。     

几丁质酶的研究进展

几丁质是自然界中含量仅次于纤维素的第二大类多糖,已从各种细菌、真菌、植物、哺乳动物和昆虫中分离并鉴定出来。随着近年来对几丁质及其衍生物的了解,发现此类多糖的物理化学特性在现实中有非常广泛的应用。几丁质酶是一类分解几丁质的酶,广泛分布于细菌、真菌、植物、哺乳动物、昆虫等物种中,并发挥着重要作用。近年来国内外工作者对这些不同来源的几丁质酶做了深入研究,为其在医学和农业上更广泛的应用提供理论基础。     

曲霉F—817菌株几丁质酶的产生条件

从采自河南各地的三十一份土样中的分离筛选到一档能分泌外几丁质酶的曲霉（Ａｓｐｅｒｇｉｌｌｕｓｓｐ．）Ｆ－８１７。该菌株几丁质酶产生的最知适碳源是１％的胶体几丁质,表面活性剂Ｔｗｅｅｎ－２０,Ｔｗｅｅｎ－８０能显著提高酶的产量,产酶的最适温度和起始ｐＨ值分别是２８～３２℃及ｐＨ５。     

病原性丝状真菌的菌种保藏方法

目的 探讨常见病原性丝状真菌的菌种保藏方法.方法将73株病原性丝状真菌经过纯化后,接种于马铃薯葡萄糖琼脂斜面分别在4℃和-80℃冷冻管保存,均用10％ (v/v)的丙三醇作为保护剂.结果经过1 a左右的保存,将菌株复活,发现4℃斜面保藏法菌株的存活率为100％,-80℃冷冻管保藏法菌株的存活率为98.6％,有些毛癣菌属...     

Immunolocalization of chitin synthases in the phytopathogenic dimorphic fungus Ustilago maydis

Conserved polypeptides of the chitin synthase genes UmCHS3 and UmCHS6 from the phytopathogenic fungus Ustilago maydis were utilized as immunogens to obtain polyclonal antibodies that were purified by affinity procedures. Because of their similarities at the regions encoded by either polypeptide, it was concluded that anti-Chs3 antibodies recognized both Chs3 and Chs4 chitin synthases, whereas anti-Chs6 antibodies recognized Chs6 and Chs8 polypeptides. These antibodies were used to analyze the localization of the corresponding chitin synthases in U. maydis cells, using both indirect immunofluorescence microscopy and immunoelectron microscopy with colloidal-gold-labeled secondary antibodies. It was observed that chitin synthase proteins were accumulated both in the surface and in the cytoplasm of the fungal cells. Electron microscopy images revealed the accumulation of clusters of gold particles in vesicles, providing evidence for the possible origin and destination of chitin synthases in the fungal cells.     

氮源受限条件下植物病原真菌氮调控基因表达特性

研究证实植物病害的发生往往是由于植物病原真菌分泌的效应子诱导引起的,在此过程中,调控效应基因表达能够了解病原菌的侵染过程。细胞的营养状况据推测对于效应基因的表达起着重要的作用。已有研究表明在氮胁迫条件下相同效应基因的诱导作用在植株体内和体外是一致的,表明氮源缺乏的环境在植物体进化的早期就已经存在了。文章阐述了在氮受限条件下真菌致病系统中效应基因调控机制及其已经发现的氮调节基因特异性表达研究结果,通过对比几个病原菌中氮调控基因的功能,比较寄主植物体内和体外在氮限制条件下基因的诱导效应,从而揭示出氮的有效性在寄主植物病害发展过程中起到重要作用。     

Characterization of chitin synthases from Entamoeba

A major component of the Entamoeba cyst wall is chitin, a homopolymer of beta-(1,4)-linked N-acetyl-D-glucosamine. Polymerization of chitin requires the presence of active chitin synthases (CHS), a group of enzymes belonging to the family of beta-glycosyl transferases. CHS have been described for fungi, insects, and nematodes; however, information is lacking about the structure and expression of this class of enzymes in protozoons such as Entamoeba. In this study, the primary structures of two putative E. histolytica CHS (EhCHS-1 and EhCHS-2) were determined by gene cloning and homologous proteins were identified in databases from E. dispar and the reptilian parasite E. invadens. The latter constitutes the widely used model organism for the study of Entamoeba cyst development. The two ameba enzymes revealed between 23% and 33% sequence similarity to CHS from other organisms with full conservation of all residues critically important for CHS activity. Interestingly, EhCHS-1 and EhCHS-2 differed substantially in their predicted molecular weights (73 kD vs. 114 kD) as well as in their isoelectric points (5.04 vs. 8.05), and homology was restricted to a central stretch of about 400 amino acid residues containing the catalytic domain. Outside the catalytic domain, EhCHS-1 was predicted to have seven transmembrane helices (TMH) of which the majority is located within the C-terminal part, resembling the situation found in yeast; whereas, EhCHS-2 is structurally related to nematode or insect chitin synthases, as it contained 17 predicted TMHs of which the majority is located within the N-terminal part of the molecule. Northern blot analysis revealed that genes corresponding to CHS-1 and CHS-2 are not expressed in Entamoeba trophozoites, but substantial amounts of CHS-1 and CHS-2 RNA were present 4 to 8 hours after induction of cyst formation by glucose deprivation of E. invadens. The time-courses of expression differed slightly between the two ameba CHS genes, as in contrast to CHS-1 RNA, expression of CHS-2 RNA was more transient and no plateau was observed between 8 and 16 hours of encystation. However, both CHS RNAs were no longer detectable after 48 hours when most of the cells had been transformed into mature cysts.     

Evolution and phylogenetic relationships of chitin synthases from yeasts and fungi

Chitin, the structural component that provides rigidity to the cell wall of fungi is the product of chitin synthases (Chs). These enzymes are not restricted to fungi, but are amply distributed in four of the five eukaryotic 'crown kingdoms'. Dendrograms obtained by multiple alignment of Chs revealed that fungal enzymes can be classified into two divisions that branch into at least five classes, independent of fungal divergence. In contrast, oomycetes and animals each possess a single family of Chs. These results suggest that Chs originated as a branch of beta-glycosyl-transferases, once the kingdom Plantae split from the evolutionary line of eukaryotes. The existence of a single class of Chs in animals and Stramenopiles, against the multiple families in fungi, reveals that Chs diversification occurred after fungi departed from these kingdoms, but before separation of fungal groups. Accordingly, each fungal taxon contains members with enzymes belonging to different divisions and classes. Multiple alignment revealed the conservation of specific motifs characteristic of class, division and kingdom, but the strict conservation of only three motifs QXXEY, EDRXL and QXRRW, and seven isolated amino acids in the core region of all Chs. Determination of different structural features in this region of Chs brought to light a noticeable conservation of secondary structure in the proteins.     

致病真菌对甲侵袭性的体外初步研究

目的观察不同致病真菌在体外对甲板的侵袭能力。方法将分离自甲真菌病患者的致病真菌包括白念珠菌、红色毛癣菌和短帚霉,接种到沙堡培养基中,同时将灭菌甲板埋植入接种处。第28d时,取出甲板,进行病理切片,观察真菌对甲板的侵袭能力。结果病理显示接种于红色毛癣菌及短帚霉的甲板内可见菌丝生长,而接种于白念珠菌的甲板内无菌丝生长。结论皮肤癣菌和霉菌可以在甲板内侵袭生长,而白念珠菌对甲板无侵袭能力。     

汕头地区甲真菌病病原菌流行病学研究

目的了解近年来汕头地区甲真菌病病原菌的种类和构成情况,掌握流行病学资料。方法对2005年12月～2008年12月间来我院皮肤科就诊的214例甲真菌病患者进行病甲标本真菌学检查和分析。结果214例患者分离出163株致病菌。酵母菌居首位,占53．99％,其中自念珠菌占22．09％,近平滑念珠菌占17．18％,热带念珠菌占6．75％,其他酵母菌占7．97％;皮肤癣菌居第2位,占37．42％,其中红色毛癣菌占23．93％,须癣毛癣菌占12．27％,断发毛癣菌占1．23％;霉菌居第3位,占8．59％,以曲霉和青霉为主,分别占3．07％和2．45％。结论汕头地区近年来甲真菌病病原菌为酵母菌、皮肤癣菌和霉菌,其中以红色毛癣菌、白念珠菌、近平滑念珠菌和须癣毛癣菌最常见。     

DNA序列分析用于常见致病真菌鉴定和分型

随着真菌感染的增多,仅用表型方法鉴定环境中或临床上的致病真菌不足以快速准确地诊断真菌感染疾病,近年来,分子生物学方法因快速、准确而逐步得到应用,其中DNA序列分析已成为鉴定致病真菌到种水平的重要方法。现就DNA序列分析在常见致病真菌分类鉴定及基因分型的应用加以综述。