氨基酸对白念珠菌形态学影响的研究

目的初步探讨单个氨基酸对白念珠菌形态学的影响。方法用0．67％的酵母氮源基础培养基和2％葡萄糖配制成SD合成培养基,37％恒温摇床培养,研究单个天然氨基酸对白念珠菌形态学的影响,并分别通过不添加碳源和厌氧条件下培养观察对精氨酸诱导的菌丝的影响。结果在含10mmol／L的L－精氨酸的SD液体培养基中,可见大量的菌丝。在含10mmol／L的L一半胱氨酸、L．苏氨酸、L－缬氨酸和L－色氨酸的sD液体培养基中,可见典型的酵母细胞,未见菌丝。在含10mmol／L的其他单个氨基酸的SD液体培养基中可见混合的酵母和菌丝结构。在不含氨基酸或含各种天然氨基酸的SD固体培养基上,白念珠菌的菌落均光滑。但在含10mmol／L的L-精氨酸固体培养基上,光滑的菌落周围可见小的突起,镜下可见菌丝。无氧条件下,无论有无碳源,含精氨酸的SD培养液中白念珠菌只能形成酵母细胞,生长部分受到抑制。结论精氨酸可以诱导白念珠菌菌丝形成,厌氧条件下精氨酸不能诱导白念珠菌菌丝形成。     

大蒜素对白念珠菌形态转换的影响研究

目的探讨大蒜素对白念珠菌形态转换的影响及其作用机制。方法倒置显微镜观察白念珠菌菌丝形成的体外动力学过程;采用CLSI-M27-A3微量液基稀释法检测大蒜素对白念珠菌的最小抑菌浓度(minimum inhibitory concentration,MIC);倒置显微镜观察不同浓度大蒜素对白念珠菌在Spider液体培养基中菌丝形成的影响;qRT-PCR法检测在不同浓度大蒜素作用下白念珠菌菌丝相关基因HWP1、ALS1、EFG1、PDE2表达水平的变化。结果白念珠菌在Spider液体培养基中6 h时出现较长菌丝,24 h后镜下可见大量念珠菌菌丝包裹酵母细胞,紧密交错;大蒜素对白念珠菌的MIC值为25μg/mL;倒置显微镜观察(25~100)μg/mL浓度的大蒜素能明显抑制Spider液体培养基中白念珠菌菌丝的生长;qRT-PCR结果显示,在(25~100)μg/mL浓度的大蒜素作用下,白念珠菌菌丝相关基因表达下调。结论大蒜素能有效抑制白念珠菌的形态转换,其作用机制可能与调节菌丝形成相关基因的表达水平有关。     

尖顶羊肚菌液体培养基质与条件的研究

通过对尖顶羊肚菌液体培养基质与条件的研究,明确其菌丝生长的最适pH值、最适温度、适宜光照条件、适宜葡萄糖和蛋白胨浓度、适宜培养基,以便应用于尖顶羊肚菌液体菌种的生产和工业发酵。结果表明:菌丝的最适生长温度为2 5℃;最适生长pH值为6 ;葡萄糖和蛋白胨最适浓度分别为2 0 0g/L和10g/L ;菌丝在黑暗环境下生长良好,光照对菌丝生长具有抑制作用;用胡萝卜酵母膏培养基振荡培养形成的菌丝球多,菌丝生长量大;菌丝球在不同培养基中生长,可引起培养液pH值的上升或者下降;菌丝球可利用培养基内的氨基酸,使氨基酸降解,在胡萝卜酵母膏培养基中振荡培养8d的菌液总氨基酸含量较原液减少了36 71% ,亮氨酸、异亮氨酸和甲硫氨酸含量的下降幅度最大     

酵母相和菌丝相白念珠菌感染阴道上皮细胞免疫反应的比较

目的白念珠菌作为一种二相菌,存在酵母相和菌丝相二态,本实验研究这两种不同形态的白念珠菌刺激阴道上皮细胞,比较其引起的免疫应答差异。方法以阴道上皮细胞株VK2/E6E7为模型,分别给予不同浓度的活的白念珠菌和热灭活白念珠菌SC5314(感染指数MOI分别为10、50、100)进行刺激,以实时荧光定量PCR(RT-qPCR)和酶联免疫吸附法(ELISA)检测3 h、6 h、12 h感染组细胞的促炎因子TNF-α和趋化因子IL-8的分泌水平。结果活的白念珠菌在K-SFM细胞培养基中呈菌丝相,热灭活的白念珠菌在K-SFM培养基中呈酵母相。两相感染组分泌IL-8和TNF-α水平与未感染组相比具有显著差异。在各个MOI条件下,菌丝相感染组释放细胞因子mRNA水平均显著高于酵母相;在MOI=10时,菌丝相感染组释放细胞因子的蛋白水平强于酵母相感染组,而随着MOI的增大,结果相反。结论酵母相和菌丝相白念珠菌均能诱发阴道上皮细胞出现显著免疫反应。同时,在MOI=10时,菌丝相白念引起的免疫反应强于酵母相白念。两相感染组免疫反应强度的差异提示两者引起免疫应答的机制可能不同。     

7种甲真菌病致病菌的侵袭力比较

目的观察红色毛癣菌、白念珠菌、红酵母、短帚霉、串珠镰刀菌、烟曲霉、绳状青霉是否具有侵犯离体甲板的能力,并比较其侵袭能力的强弱。方法将无菌甲板接种于红色毛癣菌、白念珠菌、红酵母、短帚霉、串珠镰刀菌、烟曲霉、绳状青霉7种真菌的3种不同培养基(固体沙氏培养皿、液体沙氏试管及生理盐水试管)中,定期用NaOH溶甲法分析甲板受侵程度。结果某些非皮肤癣菌性丝状真菌侵犯体外甲板的能力与红色毛癣菌基本相同,但丝状真菌比酵母菌强,酵母菌中白念珠菌比红酵母强。同一种真菌在固体培养基上对甲板的侵袭力远比在液体培养基中或生理盐水中强。结论一定条件下,某些非皮肤癣菌也能直接侵犯甲板。真菌侵犯甲的能力与其形成菌丝的能力及其与甲板接触的稳定性成正比。     

家蝇抗菌肽AMP-17对白色念珠菌菌丝的抑制作用

【背景】AMP-17是从微生物诱导的家蝇转录组数据库筛选到的一条特异性高表达基因,采用原核表达体系获得其重组蛋白并证实了具有显著的抗菌效果,特别是对白色念珠菌具有较强的抗菌活性。【目的】研究抗菌肽AMP-17对白色念珠菌菌丝的抑制作用。【方法】采用微量液体稀释法测定AMP-17对11株白色念珠菌的最小抑菌浓度(minimal inhibitory concentration,MIC);根据对AMP-17的敏感程度选取3株绘制生长曲线;通过光学显微镜观察并计数经AMP-17作用后白色念珠菌芽生孢子生成率及芽管形成率;倒置荧光显微镜观察白色念珠菌酵母相向菌丝相转化及以菌丝相为起点AMP-17促进菌丝相转化为酵母相的情况。【结果】AMP-17对支气管肺泡灌洗液分离株16105的MIC为10μg/mL,对粪便分离株16214的MIC为40μg/mL,对其余9株白色念珠菌的MIC均为20μg/mL;白色念珠菌经不同浓度的AMP-17作用后,各时间点的芽生孢子生成率均显著低于对照组,尤其是40μg/mL的AMP-17组,芽生孢子生成率仅15%,显著低于阳性药物氟康唑;各实验组芽管形成率显著低于对照组,且芽管形成缓慢,培养6 h后芽管形成率仅为6%,形成的芽管长度较短,仅为菌体的1-2倍。镜下观察低浓度的AMP-17即可以完全抑制白色念珠菌菌丝的生长,并且对已经形成的菌丝有一定的生长抑制作用,高浓度的AMP-17则可使已形成的部分菌丝向酵母相转化。【结论】家蝇抗菌肽AMP-17可抑制白色念珠菌菌丝生长。     

白念珠菌酵母相与菌丝相对5种抗真菌药物的敏感性比较

目的比较白念珠菌酵母相与菌丝相对常用抗真菌药物的敏感性的差异,为病原真菌学研究及临床用药提供理论指导。方法应用法国生物-梅里埃ATB FUNGUS 3药敏试剂盒对临床分离的220株白念珠菌进行抗真菌药物的敏感性测定。结果 220株白念珠菌酵母相与菌丝相对两性霉素B、氟康唑、伊曲康唑、伏立康唑、5-氟胞嘧啶5种常用的抗真菌药物的敏感率分别为97.27%与97.73%,81.82%与85.00%,87.27%与90.46%,92.72%与95.00%,96.82%与97.27%。氟康唑、伊曲康唑和伏立康唑对白念珠菌酵母相MIC值明显高于菌丝相,差异有显著性(P0.05),两性霉素对白念珠菌酵母相和菌丝相MIC值差异不显著(P0.05)。受试菌株两相细胞对5种抗真菌药物敏感度总体一致性为85.46%(188/220),有32株菌株酵母相表现为耐药及中介,但菌丝相却为中介与敏感。结论白念珠菌酵母相和菌丝相对5种抗真菌药物的敏感性存在差异,抗真菌药物对菌丝相的抗菌活性强于酵母相。     

刺芹侧耳生长条件和栽培特性的研究

对刺芹侧耳[Pleurotus eryngii(DC.ex Fr.)Quel]生长条件与栽培特性进行了分析.结果表明:刺芹侧耳菌丝生长的适宜pH值为pH 5～pH 7,最适pH值为pH 6;黑暗环境有利于菌丝生长,光照对菌丝生长具有抑制作用;菌丝生长适宜的碳源为可溶性淀粉、葡萄糖和蔗糖,适宜的氮源为蛋白胨和钼酸铵,葡萄糖和蛋白胨的适宜浓度分别为50和1 g·L-1;在马铃薯黄豆粉培养基、黄豆粉玉米粉培养基和马铃薯蛋白胨培养基中可较好地形成菌丝球.采用液体菌种栽培,菌丝的生长速度比使用玉米固体菌种快,其中用马铃薯黄豆粉液体菌种栽培,菌丝生长最快;使用马铃薯蛋白胨液体菌种在木屑棉籽壳混合培养料中栽培,可获得菌柄长菌盖大的子实体,而且产量高.     

环境pH诱导出芽短梗霉细胞多形化

出芽短梗霉具有酵母状细胞、膨大细胞、菌丝、厚垣孢子、念珠状菌丝和分生组织状结构。在最适pH条件下,出芽短梗霉生长繁殖以酵母状细胞（CBS100225等4菌株）或膨大细胞（CBS249.65等4菌株）为主。pH 2.2或pH 7.0诱导全部8株出芽短梗霉形成分生组织状结构。酵母状细胞转变成膨大细胞受低pH值诱导的占75%,还受高pH诱导的占50%。膨大细胞是多形性细胞转变的中心环节,可以转变成菌丝、厚垣孢子或分生组织状结构。     

硼酸抗白念珠菌作用的试验研究

目的探讨硼酸对白念珠菌临床分离株菌株的生长状态和细胞形态的影响。方法用加入0%、0.1%、0.15%硼酸(w/v)的Lee’s glucose培养基于25℃和37℃分别培养8株临床分离的白念珠菌,观察各菌株在不同培养条件下生长状况。结果 25℃培养条件下,0.1%的硼酸明显抑制白念珠菌生长,其中对HJ065的抑制效果最明显,0.15%的硼酸进一步抑制白念珠菌生长,并且SC5314、HJ058菌株的菌丝生长能力随硼酸浓度增高而减弱。37℃培养条件下,硼酸对白念珠菌生长状态和菌丝生长能力的抑制效果较25℃更明显。相同培养条件下,硼酸对不同CAI重复数的白念珠菌的抑制效应存在差异。结论硼酸对白念珠菌临床分离菌株的抑制作用表现出明显菌株的差异性。其抑制作用与培养温度有关:表现为生理温度下抑制作用更明显。硼酸对8株白念珠菌抑制作用与CAI的重复数无明显相关性。     

Dimorphism and virulence in Candida albicans

Two regulatory pathways govern filamentation in the pathogenic fungus Candida albicans. Recent virulence studies of filamentation regulatory mutants argue that both yeast and filamentous forms have roles in infection. Filamentation control pathways seem closely related in C. albicans and in Saccharomyces cerevisiae, thus permitting speculation about C. albicans filamentation genes not yet discovered.     

Factors affecting spore formation in a Candida albicans strain

Growth and spore formation of Candida albicans Y-45 was enhanced by low oxygen tension. Mycelium and chlamydospores were abundantly found on rice infusion-Tween 80 agar within 48 to 96 h, and abundant chlamdospore production occurred most rapidly under reduced oxygen tension and incubation at 30 degrees C. Zn, Mg, Mn, anf Fe were tested for their ability to promote filamentation in C. albicans Y-45. Filamentation under conditions of low Mg and high Mn suggested that morphogenesis is possibly correlated with the presence of salts of these heavy metals.     

Factors affecting spore formation in a Candida albicans strain.

Growth and spore formation of Candida albicans Y-45 was enhanced by low oxygen tension. Mycelium and chlamydospores were abundantly found on rice infusion-Tween 80 agar within 48 to 96 h, and abundant chlamdospore production occurred most rapidly under reduced oxygen tension and incubation at 30 degrees C. Zn, Mg, Mn, anf Fe were tested for their ability to promote filamentation in C. albicans Y-45. Filamentation under conditions of low Mg and high Mn suggested that morphogenesis is possibly correlated with the presence of salts of these heavy metals.     

Invasive filamentous growth of Candida albicans is promoted by Czf1p-dependent relief of Efg1p-mediated repression

Filamentation of Candida albicans occurs in response to many environmental cues. During growth within matrix, Efg1p represses filamentation and Czf1p relieves this repression. We propose that Czf1p interacts with Efg1p, altering its function. The complex regulation of filamentation may reflect the versatility of C. albicans as a pathogen.     

CaSRB9基因的克隆及其在酿酒酵母形态发生中的作用

白色念珠菌是一种重要的人体致病真菌 ,致病机制与其形态发生紧密相关。酿酒酵母Flo8因子在其形态发生中起重要作用 ,我们把白色念珠菌基因组DNA导入酿酒酵母flo8基因缺失株中 ,筛选能够互补 flo8侵入生长缺陷的基因 ,分离到了一个与酿酒酵母SRB9同源的新基因 ,命名为CaSRB9。该基因全长 4998bp ,编码一种16 6 5个氨基酸的蛋白质。在双倍体酿酒酵母中CaSRB9可以部分互补MAPK途径基因缺失株以及 flo8缺失株的菌丝生长缺陷 ;在单倍体酿酒酵母中表达能够互补 flo8缺失株的侵入生长缺陷 ,但在MAPK途径基因缺失株中不能形成侵入生长     

Dominant active alleles of RIM101 (PRR2) bypass the pH restriction on filamentation of Candida albicans

Morphological development of the fungal pathogen Candida albicans is profoundly affected by ambient pH. Acidic pH restricts growth to the yeast form, whereas neutral pH permits development of the filamentous form. Superimposed on the pH restriction is a temperature requirement of approximately 37 degrees C for filamentation. The role of pH in development was investigated by selecting revertants of phr2Delta mutants that had gained the ability to grow at acid pH. The extragenic suppressors in two independent revertants were identified as nonsense mutations in the pH response regulator RIM101 (PRR2) that resulted in a carboxy-terminal truncation of the open reading frame. These dominant active alleles conferred the ability to filament at acidic pH, to express PHR1, an alkaline-expressed gene, at acidic pH, and to repress the acid-expressed gene PHR2. It was also observed that both the wild-type and mutant alleles could act as multicopy suppressors of the temperature restriction on filamentation, allowing extensive filamentation at 29 degrees C. The ability of the activated alleles to promote filamentation was dependent upon the developmental regulator EFG1. The results suggest that RIM101 is responsible for the pH dependence of hyphal development.     

Fungal adenylyl cyclase integrates CO2 sensing with cAMP signaling and virulence

The ascomycete Candida albicans is the most common fungal pathogen in immunocompromised patients . Its ability to change morphology, from yeast to filamentous forms, in response to host environmental cues is important for virulence . Filamentation is mediated by second messengers such as cyclic adenosine 3',5'-monophosphate (cAMP) synthesized by adenylyl cyclase . The distantly related basidiomycete Cryptococcus neoformans is an encapsulated yeast that predominantly infects the central nervous system in immunocompromised patients . Similar to the morphological change in C. albicans, capsule biosynthesis in C. neoformans, a major virulence attribute, is also dependent upon adenylyl cyclase activity . Here we demonstrate that physiological concentrations of CO2/HCO3- induce filamentation in C. albicans by direct stimulation of cyclase activity. Furthermore, we show that CO2/HCO3- equilibration by carbonic anhydrase is essential for pathogenesis of C. albicans in niches where the available CO2 is limited. We also demonstrate that adenylyl cyclase from C. neoformans is sensitive to physiological concentrations of CO2/HCO3-. These data demonstrate that the link between cAMP signaling and CO2/HCO3- sensing is conserved in fungi and reveal CO2 sensing to be an important mediator of fungal pathogenesis. Novel therapeutic agents could target this pathway at several levels to control fungal infections.