人类致病菌新型隐球酵母Snf1/AMPK 蛋白激酶调节细胞壁的完整性

摘要：【目的】Snf1/AMPK在真核生物中是重要的且高度保守的一类蛋白激酶。在新型隐球酵母中,SNF1 基因在调节致病因子的生物合成和细胞毒力方面具有重要作用。本文进一步报道了该基因在维持细胞壁完整方面的新功能,这一功能在其他微生物中未见报道。【方法】利用荧光增白剂染料（Calcofluor white dye）染色,荧光显微观察细胞分离、胞壁完整性;利用恒定流速和压力水流冲击菌落,测定细胞黏附琼脂糖表面能力;在含有十二烷基硫酸钠（Sodium dodecyl sulfate,SDS）,刚果红（Congo red）染料和增白剂（Fluorescent Brightener 28）的培养基上观察突变株的生长情况,以验证细胞壁完整性。【结果】SNF1 基因突变菌株对细胞壁抑制剂SDS等敏感,表明细胞壁完整性的损坏;在葡萄糖固体培养基上表现为细胞与琼脂间的黏附力丧失;在热击压力下,该菌株不能正常生长,而这种生长缺陷能够被渗透平衡抑制。【结论】新型隐球酵母SNF1 基因对于维持细胞壁完整性是非常重要的,并且影响细胞与琼脂间黏附作用以及细胞对抗热的能力。     

MIG1基因和葡萄糖对扣囊复膜孢酵母细胞形态变化的影响及机理探究

【目的】研究MIG1基因和葡萄糖对扣囊复膜孢酵母细胞形态变化的影响及其机理探究。【方法】扣囊复膜孢酵母在不同浓度葡萄糖的YPD培养基中培养,敲除MIG1基因菌株在常规YPD培养基中培养,研究细胞内葡聚糖酶和几丁质酶活性以及细胞壁β-葡聚糖和几丁质含量与细胞形态变化之间的关系。【结果】培养基中葡萄糖浓度越低,扣囊复膜孢酵母菌丝体越少,单细胞酵母越多,且葡聚糖酶和几丁质酶活性越高,β-葡聚糖和几丁质含量越低;葡萄糖浓度对敲除MIG1基因菌株没有显著影响,葡聚糖酶和几丁质酶活性始终保持在较高水平,β-葡聚糖和几丁质含量也较低,菌体多以单细胞酵母形式存在。【结论】MIG1基因和葡萄糖通过葡萄糖阻遏作用调节葡聚糖酶和几丁质酶活性,进而影响细胞壁的葡聚糖和几丁质含量,最终影响扣囊复膜孢酵母细胞的形态变化。     

破坏细胞壁蛋白CWP2基因提高重组酿酒酵母β-葡萄糖苷酶胞外酶活

【背景】重组酿酒酵母广泛应用于生产工业酶和药用蛋白,但是目前仍旧存在异源蛋白产量低、分泌效率差的问题,限制了生产应用。【目的】提高重组酿酒酵母异源分泌蛋白的能力,构建高效的异源蛋白生产细胞工厂。【方法】采用基于CRISPR/Cas9的基因组编辑技术,以生产β-葡萄糖苷酶的重组酿酒酵母Y294-BGL为出发菌株,构建细胞壁蛋白基因CWP2破坏菌株。【结果】与出发菌株相比,破坏CWP2的破坏菌株在发酵96 h时胞外β-葡萄糖苷酶酶活可提高53%,胞内酶活提高了208%。此外,破坏菌生长未受到影响,对弱酸等环境胁迫的耐性没有下降,未造成过多内质网胁迫。进一步检测发现,破坏菌株胞内活性氧水平下降,同时蛋白胞内运输和分泌途径相关的关键基因表达转录及多个细胞壁生物合成相关基因表达下降。【结论】破坏细胞壁蛋白基因CWP2能够提高异源蛋白β-葡萄糖苷酶的胞外酶活,可作为促进酿酒酵母生产异源蛋白的靶点基因。     

AsSlt2基因对茄链格孢细胞壁完整性的调控

【背景】由茄链格孢(Alternaria solani)引起的马铃薯早疫病被普遍认为是马铃薯生产上的第二大叶部病害,在马铃薯各产区普遍发生,给马铃薯生产造成了巨大的经济损失。【目的】明确AsSlt2基因对茄链格孢细胞壁完整性的影响。【方法】在含有刚果红、细胞壁降解酶和十二烷基硫酸钠(sodiumdodecylsulfate,SDS)等细胞壁胁迫的培养基上观察ΔAsSlt2缺失突变株的生长情况,计算相对生长抑制率;通过实时荧光定量PCR (RT-qPCR)方法检测ΔAsSlt2菌株中细胞壁合成相关基因的表达情况;进一步检测ΔAsSlt2细胞壁中几丁质的含量及胞外酶活性。【结果】ΔAsSlt2缺失突变株对SDS、刚果红、细胞壁降解酶等细胞壁胁迫的敏感性增强,在加入细胞壁降解酶后突变株原生质体释放量显著增多;ΔAsSlt2对外源氧胁迫更敏感,突变株胞外过氧化物酶和漆酶活性均显著降低;进一步研究发现,ΔAsSlt2细胞壁中几丁质含量减少,几丁质合成相关基因与漆酶合成相关基因的表达量均明显降低。【结论】AsSlt2基因在茄链格孢细胞壁的完整性及抵御外界胁迫方面发挥重要作用。     

白头翁汤正丁醇提取物对白念珠菌细胞壁抑制作用研究

目的探讨白头翁汤正丁醇提取物(Butyl alcohol extract of BaiTouWeng decoction,BAEB)对白念珠菌细胞壁的抑制作用。方法以spot assay检测BAEB对白念珠菌细胞活性的影响;流式细胞仪和酶标仪检测BAEB对白念珠菌细胞壁β-1,3-葡聚糖及几丁质变化;qRT-PCR检测白念珠菌细胞壁β-1,3-葡聚糖合成相关基因FKS-1及几丁质合成相关基因CHS1、CHS2、CHS3、CHS8的表达;透射电镜观察BAEB对白念珠菌细胞壁结构影响。结果 BAEB干预后白念珠菌活性降低,256、512、1 024μg/mL BAEB组白念珠菌细胞壁β-1,3-葡聚糖暴露与几丁质暴露逐渐增多(P0.05);1 024μg/mL BAEB干预组FKS1、CHS1、CHS2、CHS3、CHS8分别下调5.57、2.96、3.29、4.47、3.00倍;透射电镜观察BAEB干预后白念珠菌细胞壁结构有破损。结论 BAEB可通过增加β-1,3-葡聚糖和几丁质的暴露,抑制β-1,3-葡聚糖、几丁质及其生物合成相关基因的表达,进而破坏白念珠菌细胞壁完整性。     

敲除MIG1和SNF1基因对酿酒酵母共利用葡萄糖和木糖的影响

Mig1和Snf1是酿酒酵母葡萄糖阻遏效应的两个关键调控因子。为了提高酿酒酵母工程菌同时利用葡萄糖和木糖的能力,分别对MIG1和SNF1基因进行了单敲除和双敲除,并通过摇瓶发酵实验和RNA-Seq转录组分析,初步揭示了Mig1和Snf1可能影响葡萄糖和木糖共利用表达差异基因的层级调控机制。研究结果表明,MIG1单敲除对混合糖的共利用影响不大;SNF1单敲除会加快混合糖中木糖的利用而且葡萄糖和木糖可以被同时利用,这可能归因于SNF1单敲除会解除对一些氮分解代谢阻遏基因表达的抑制,从而促进了细胞对氮源营养的利用;进一步敲除MIG1,会解除更多氮分解代谢阻遏基因表达的抑制,以及一些碳中心代谢途径基因表达上调。虽然MIG1和SNF1双敲除菌株利用葡萄糖加快而利用木糖变慢,但是葡萄糖和木糖可以被同时利用,进而加快乙醇的积累。综上所述,MIG1和SNF1的敲除导致氮分解阻遏基因表达上调,有助于促进葡萄糖和木糖的共利用;解析Mig1和Snf1对氮分解阻遏基因的层级调控作用,为进一步提高葡萄糖和木糖的共利用提供新的靶点。     

大肠杆菌BL21(DE3)膜组分相关基因的敲除对重组蛋白胞外分泌的影响

摘要:【目的】探究Escherichia coli BL21(DE3)中膜组分相关的脂多糖合成基因waaF或msbB的敲除对重组蛋白胞外分泌的影响。【方法】运用Red重组技术将E.coli BL21 (DE3)染色体上的基因waaF或msbB敲除,构建敲除菌株E.coli BL21(ΔwaaF)、E.coli BL21(ΔmsbB)。将本实验室保存的带有β-呋喃果糖苷酶(β-fructofuranosidase,β-FFase)、青霉素G 酰化酶(penicillin G acylase,PGA)基因的重组质粒pET-ffase、pET-pga分别转入敲除菌株及出发菌株中,构建工程菌株E.coli BL21(ΔmsbB)/pET-ffase、E.coli BL21(ΔwaaF)/pET-ffase、E.coli BL21(DE3)/pET-ffase、E.coli BL21(ΔmsbB)/pET-pga、E.coli BL21(ΔwaaF)/pET-pga、E.coli BL21(DE3)/pET-pga。最后通过摇瓶发酵研究敲除菌株对β-FFase、PGA胞外分泌的影响。【结果】当诱导表达4 h,以出发菌株E.coli BL21(DE3)为宿主时,β-呋喃果糖苷酶β-FFase的胞外分泌量占总表达量的2.6%,以敲除菌株ΔmsbB为宿主时,胞外分泌量达到19.7%,而以敲除菌株ΔwaaF为宿主时,胞外分泌量达到50.9%。另外,当诱导表达24 h,以敲除菌株ΔwaaF为宿主时,青霉素G酰化酶PGA的胞外酶活是出发菌株中的4.1倍,达到1708 U/L。【结论】本研究成功构建了敲除菌株ΔmsbB和ΔwaaF,ΔmsbB能明显增强β-FFase的胞外分泌,而ΔwaaF对β-FFase和PGA的胞外分泌均有显著的强化作用。     

H4K5去乙酰化对镍胁迫下酿酒酵母细胞壁完整性途径的调控作用

【目的】金属镍(nickel, Ni)是人类广泛接触的重金属污染物之一,镍暴露会激活细胞内的细胞壁完整性(cell wall integrity, CWI)信号通路,也会导致细胞内组蛋白乙酰化水平降低,但CWI途径在镍胁迫时是否受组蛋白乙酰化调控尚不完全清楚。【方法】利用组蛋白定点突变型菌株H4K5R (模拟去乙酰化状态),分析镍胁迫下H4K5去乙酰化对酿酒酵母CWI途径的调控作用【结果】与野生型菌株相比,定点突变型菌株H4K5R具有较强的镍抗性:在5.0 mmol/L NiCl₂胁迫下,定点突变型菌株仍能生长良好;Western blotting与qRT-PCR结果表明,野生型菌株BY4741在5.0 mmol/L NiCl₂胁迫下细胞壁完整性途径被激活,甘露聚糖与葡聚糖调控基因Mnn9表达量显著上调3.13倍、Fks1表达量显著上调1.49倍,甘露聚糖、β-葡聚糖的含量也增加,说明此时野生型菌株激活了CWI途径,细胞壁成分含量增加;定点突变型菌株H4K5R在5.0 mmol/L NiCl₂胁迫下CWI途径激活程度较轻,虽然Mnn9、Fks1表达量上调,但甘露聚糖含量变化并不显著,而相较于野生型菌株β-葡聚糖含量增加幅度较小。【结论】在5.0 mmol/L NiCl₂胁迫下,定点突变型菌株H4K5位点的去乙酰化调控CWI途径,进而影响细胞壁组分的变化。     

酿酒酵母NST1基因敲除菌的构建及其对抗氧化的影响

构建一株酿酒酵母(Saccharomyces cerevisiae)NST1基因缺失菌株并研究其对抗氧能力的影响。以酿酒酵母BY4741中的NST1基因为研究对象,利用Cre-LoxP基因敲除系统将NST1基因与G418抗性基因(kan~r)相替换,实现目的基因的敲除。通过稀释点样实验、荧光电子显微镜检测和荧光定量PCR等技术分析NST1基因在酿酒酵母抗氧化体系中的作用。经过G418抗性筛选和基因组PCR鉴定,成功获得了NST1基因缺失菌株nst1Δ,实验数据显示nst1Δ重组菌胞内ROS增多,并且降低了细胞壁完整性信号通路(CWI)途径下游基因RLM1的表达水平,表明NST1基因的敲除对酿酒酵母BY4741的抗氧化性能有影响。     

酿酒酵母Mbp1缺陷型菌株的构建及其乙醇发酵特性

【目的】研究酿酒酵母(Saccharomyces cerevisiae)工业菌株Mbp1基因的功能,探讨Mbp1基因对酿酒酵母乙醇发酵性能的影响。【方法】以酿酒酵母MF1015为出发菌株,用PCR方法构建Mbp1基因敲除组件Loxp-KanMX-Loxp,将敲除组件转化两种配型的酿酒酵母单倍体,通过单倍体复倍获得敲除Mbp1基因的二倍体突变菌株,研究突变菌株形态变化及乙醇发酵特性。【结果】敲除Mbp1基因后突变菌株生长曲线无显著变化,出芽率降低,细胞体积增大19.2%,对饥饿更敏感,较早出现假菌丝。甘蔗糖蜜在静置条件下发酵,突变菌株的乙醇产量明显低于野生型;在130 r/min的条件下发酵,突变菌株和野生型发酵液中的乙醇产量基本相同。【结论】Mbp1基因缺失使酿酒酵母的乙醇发酵能力下降并影响细胞的形态分化。     

Induction kinetics of the Staphylococcus aureus cell wall stress stimulon in response to different cell wall active antibiotics

Background  

Staphylococcus aureus activates a protective cell wall stress stimulon (CWSS) in response to the inhibition of cell wall synthesis or cell envelope damage caused by several structurally and functionally different antibiotics. CWSS induction is coordinated by the VraSR two-component system, which senses an unknown signal triggered by diverse cell wall active agents.     

The plant cell wall

<正>Research on the many aspects of the plant cell wall has experienced rejuvenation during the past few years.This is perhaps mainly due to the commercial interest in the chemical components of the cell wall that have potential for industrial use:Cellulose for fi bers and together with hemicelluloses for bioethanol,lignin for plastics or biofuel,pectins as gel agents,let alone woody cell wall material for construction or pulp     

An arabinogalactoxyloglucan from the cell wall of Solanum tuberosum

Cell-wall material from potatoes was fractionated by successive extractions with water at 80°, 0.2 M (NH₄)₂C₂O₄ at 80°, 1 M and 4 M KOH, to leave a residue of α-cellulose. The compositions of the isolated carbohydrate polymers were determined by sugar and methylation analysis. From the 4M KOH-soluble fraction an arabinogalactoxyloglucan was isolated and (partially) characterized by methylation analysis of the undegraded polymer and partially degraded methylated polymer. Methylation analysis of the oligosaccharides produced on treatment of the xyloglucan with cellulase threw additional light on the structural features of the polysaccharide. The results show that the xyloglucan has a cellulosic backbone which is highly substituted at position 6 with xylopyranose residues, some of which, in turn, carry either arabinofuranose or galactopyranose residues, as a substituent on position 2. The significance of these results is discussed.     

Structure of polysaccharides from the Polyporus tumulosus cell wall

Cell walls of the Basidiomycete fungus Polyporus tumulosus (Cooke) were fractionated, and the polysaccharide content of the fractions investigated. The major constituents of the cell wall include four polysaccharides, chitin, a β-1, 3-glucan and the alkali soluble α-glucan and xylomannan.The glucan is highly dextrotatory with an [α]_D²¹ of + 221° and gave on partial acid hydrolysis and acetolysis an homologous series of oligosaccharides. The disaccharide was shown to be nigerose 3-0-α-D-glucopyranosyl-D-glucose. Periodate oxidation and methylation studies provided supporting evidence that the polysaccharide is an essentially unbranched polymer of 1,3-linked glucose residues.The other alkali-soluble polysaccharide, a xylomannan, is a polymer of mannose and xylose in the approximate molar proportions of 1.2:1. It has an [α]_D = + 56° and on partial acid hydrolysis and acetolysis gave an homologous series of 1,3-linked mannodextrins but no oligosaccharides containing xylose were obtained. An α-1,3-linked mannan was prepared from the xylomannan by degradation with mild acid or by degradation of the periodate-oxidased and reduced xylomannan. The structure therefore is visualised as having a backbone of 1,3-linked mannan, to which xylose residues are attached. Methylation studies showed that branching occurs at C-4 of the mannopyranose units; the presence of 2,3-di-o-methyl-d-xylose in the hydrolysate of the methylated polysaccharide indicated that some of the xylose residues are 1,4-linked. The possible structure of the fungal cell wall is discussed in the light of the results obtained.     

Raman imaging of cell wall polymers in Arabidopsis thaliana

We present chemical images of Arabidopsis thaliana stem cross-sections acquired by confocal Raman microscopy. Using green light (532 nm) from a continuous wave laser, the spatial distributions of cell wall polymers in Arabidopsis are visualized for the first time with lateral resolution that is sub-μm. Our results facilitate the label-free in situ characterization and screening of cell wall composition in this plant biology and genetics model organism, contributing ultimately towards an understanding of the molecular biology of many plant traits.     

Characterization of the cell wall and cell wall proteins of Chromatium vinosum.

Highly purified cell walls of Chromatium vinosum were isolated by differential centrifugation, with or without Triton X-100 extraction. The isolated material had a protein composition similar to that of cell walls obtained by sucrose density gradient centrifugation. Twenty-two proteins were reproducibly detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A 42-kilodalton protein was shown to account for 65% of the total cell wall protein. The majority of cell wall proteins were solubilized in sodium dodecyl sulfate at room temperature; however, they existed as high-molecular-weight complexes unless heated to 45 degrees C or above. The cell wall contained one heat-modifiable protein which migrated with an apparent molecular weight of 37,400 when solubilized at 70 degrees C or below, but which migrated with an apparent molecular weight of 52,500 if solubilized at 100 degrees C. The electrophoretic mobility of three proteins was modified by 2-mercaptoethanol. The majority of C. vinosum cell wall proteins had isoelectric points between pH 4.5 and 5.5, and the 42-kilodalton protein focused at pH 4.9. No proteins were detected which were analogous to the lipoprotein or peptidoglycan-associated proteins of the Enterobacteriaceae. Nearest-neighbor analysis with a reducible, cross-linking reagent indicated that three proteins, including the 42-kilodalton protein, associated with themselves. Most of the cell wall proteins were partially accessible to proteases in both intact cells and isolated cell walls. Protease treatment of the whole cell or isolated cell wall digested approximately an 11,000-molecular-weight portion of the 42-kilodalton protein.     

Auxin-induced cell elongation and cell wall changes

It has been well known that auxin induces cell elongation through its effect on modifications of the cell wall. The present review will discuss cell wall modifications, physical and biochemical, as the background of the former, based on the experimental results from our laboratory and from others, with the historical background. Discussions will particularly put stress on the auxin effect on the cell wall in terms of the following studies, namely, (1) measurements of the mechanical property of the cell wall, and (2) biochemical studies on the polysaccharide molecules of the cell wall. This article is dedicated to Professor Anton N.J. Heyn for his 85th birthday.