Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge

To evaluate and develop methodologies for the extraction of gel-forming extracellular polymeric substances (EPS), EPS from aerobic granular sludge (AGS) was extracted using six different methods (centrifugation, sonication, ethylenediaminetetraacetic acid (EDTA), formamide with sodium hydroxide (NaOH), formaldehyde with NaOH and sodium carbonate (Na₂CO₃) with heat and constant mixing). AGS was collected from a pilot wastewater treatment reactor. The ionic gel-forming property of the extracted EPS of the six different extraction methods was tested with calcium ions (Ca²⁺). From the six extraction methods used, only the Na₂CO₃ extraction could solubilize the hydrogel matrix of AGS. The alginate-like extracellular polymers (ALE) recovered with this method formed ionic gel beads with Ca²⁺. The Ca²⁺-ALE beads were stable in EDTA, formamide with NaOH and formaldehyde with NaOH, indicating that ALE are one part of the structural polymers in EPS. It is recommended to use an extraction method that combines physical and chemical treatment to solubilize AGS and extract structural EPS.     

Characterization of the adhesive mucilages secreted by live diatom cells using atomic force microscopy

Atomic Force Microscopy (AFM) resolved the topography and mechanical properties of two distinct adhesive mucilages secreted by the marine, fouling diatom Craspedostauros australis. Tapping mode images of live cells revealed a soft and cohesive outer mucilage layer that encased most of the diatom's siliceous wall, and force curves revealed an adhesive force of 3.58 nN. High loading force, contact mode imaging resulted in cantilever 'cleaned' cell walls, which enabled the first direct observation of the active secretion of soft mucilage via pore openings. A second adhesive mucilage consisted of strands secreted at the raphe, a distinct slit in the silica wall involved in cell-substratum attachment and motility. Force measurements revealed a raphe adhesive strand(s) resistant to breaking forces up to 60 nN, and these strands could only be detached from the AFM cantilever probe using the manual stepper motor.     

Nanoscale Mechanical Characterisation of Amyloid Fibrils Discovered in a Natural Adhesive

Using the atomic force microscope, we have investigated the nanoscale mechanical response of the attachment adhesive of the terrestrial alga Prasiola linearis (Prasiolales, Chlorophyta). We were able to locate and extend highly ordered mechanical structures directly from the natural adhesive matrix of the living plant. The in vivo mechanical response of the structured biopolymer often displayed the repetitive sawtooth force-extension characteristics of a material exhibiting high mechanical strength at the molecular level. Mechanical and histological evidence leads us to propose a mechanism for mechanical strength in our sample based on amyloid fibrils. These proteinaceous, pleated β-sheet complexes are usually associated with neurodegenerative diseases. However, we now conclude that the amyloid protein quaternary structures detected in our material should be considered as a possible generic mechanism for mechanical strength in natural adhesives.     

肌动蛋白的原子力显微镜研究

原子力显微镜 (AFM )是一种能够在生理条件下对生物大分子、活细胞表面以及细胞膜下结构进行在体或离体研究的强有力的新型工具 ,具有原子级的成像分辨率和纳牛顿级的力测定功能。目前原子力显微镜已被广泛地应用于生物大分子、超分子体系的结构解析、动力学过程观察 ,分子力学研究及细胞功能鉴定。原子力显微镜能够通过尖锐探针扫描待测样品表面 ,收集被测样品表面地貌坐标数据从而对单分子或细胞进行成像或操作 ,并能通过移动探针、记录探针与样品之间的作用力 ,对生物大分子 (蛋白质、核酸和多糖等 )的结构力学特性进行分析以获取分子构象、功能及其相互关系的有用信息。肌动蛋白是一种细胞内普遍存在 ,具有广泛、复杂生理功能的重要蛋白质 ,原子力显微镜的各项功能已广泛地用于肌动蛋白结构、功能及动力学研究。通过综述原子力显微镜在肌动蛋白研究中的应用 ,阐明了原子力显微镜在现代生命科学研究中的重要意义及巨大应用前景。     

天花粉蛋白对红细胞损伤作用的AFM研究

目的：利用原子力显微镜（atomic force microscopy,简称AFM）观察红细胞（red blood cells,简称RBC）与天花粉蛋白（trichosanthin,简称TCS）作用后形态上的变化以及细胞膜的损伤情况。方法：将1.2mg/ml的TCS溶液与红细胞的PBS缓冲溶液（pH7.4)按1：4的比例混合,在35℃温度下作用2h后,用原子力显微镜观察受损的红细胞,与正常红细胞进行对比。结果：（1）与正常红细胞相比,与TCS作用后的红细胞的高度明显降低,凹陷部分更加明显。（2）对红细胞上小范围扫描成像的结果显示,受损后的红细胞膜表面结构发生了变化,膜表面颗粒排列的特征依然存在,但颗粒之间开始产生连接。结论：TCS能损伤红细胞膜,改变细胞膜的微结构,引起红细胞的溶血作用。     

4种外生菌根真菌对难溶性磷酸盐的溶解能力

以红绒盖牛肝菌(Xerocomus chrysenteron)、美味牛肝菌(Boletus edulis)、黄须腹(Rhizopogen luteous)和劣味乳菇(Lactarius insulsus)4种外生菌根真菌为对象,在纯培养条件下比较它们对4种难溶性磷酸盐[Ca_3(PO_4)_2、Ca_(10)(PO_4)_6(OH)_2、FePO_4·4H_2O和AlPO_4]的溶解能力,以探讨外生菌根真菌对难溶性磷酸盐的溶解作用及其影响因素.结果表明:(1)4种外生菌根真菌均能在Ca_3(PO_4)_2为唯一磷源的NBRIP平板上生长,但生长速率明显不同,且红绒盖牛肝菌生长速率最快.(2) 4种菌根真菌对4种磷酸盐的溶解能力存在显著差异,红绒盖牛肝菌发酵液可溶性磷含量大多显著高于对照和其他菌根真菌,对磷酸盐的溶解能力最强.(3)4种菌根真菌发酵液可滴定酸度(2.30～46.00 mmol·L~(-1))和pH(4.57～6.99)与其溶磷量分别呈极显著正相关(r=0.991**)和极显著负相关(r=-0.939**).(4)4种外生菌根真菌均能分泌乙酸、柠檬酸和反丁烯二酸,且它们分泌有机酸总量(14.14～1 537.46 mg·L~(-1))与其溶磷量呈显著正相关(r=0.998*).研究发现, 4种外生菌根真菌发酵液可滴定酸度、pH和有机酸的种类与含量是影响其溶解Ca_3(PO_4)_2能力的主要因素;红绒盖牛肝菌的溶磷能力较强,具有应用于中国土壤缺磷地区造林的潜力.     

利用原子力显微镜对A型流感病毒的形态学研究

利用透射电子显微镜(TEM)和原子力显微镜(AFM)观察流感病毒(H1N1),探讨AFM在病毒形态研究中的应用,为病毒形态学研究提供一种新型、简便、快捷的工具.TEM采用磷钨酸负染方法,AFM采用轻敲模式在大气常温下扫描成像,并对主要指标长度(直径)、Ra、Rq等进行测量.两种方法最终得到相似的形态学结果,流感病毒呈球状、丝状,并有一些形状介于两者之间.TEM提供了流感病毒二维图像,可见钉状突起,AFM则呈现了流感病毒三维图像,且可见病毒表面有凹凸不平的特征和边缘有齿轮状的突起,同时获得表面粗糙度等可以量化指标.与TEM观察相比,原子力显微镜是一种制样简单、观察直观的新型病毒形态学研究工具,其表征参数可以作为病毒形态学研究的量化指标.     

一株结皮真菌胞外多糖的初步研究

探究一株真菌胞外多糖最佳生产时间及其组成成分。通过对其发酵液胞外多糖含量及上清液黏度的测定,确定其最佳产糖时间,并用此条件提取胞外多糖粗品,用蒽酮-比色法测得提取的胞外多糖粗品的糖含量,薄层色谱法对所得的胞外多糖进行组分分析。当发酵至第5天时该株真菌的生物量、胞外多糖产量及发酵液的黏度均达到最高峰,分别为0.606 4 g/60 mL、20.22 μg/mL和4.74 mPa/s,并且胞外多糖含量与发酵上清液黏度在一定程度上呈正相关。用蒽酮-比色法测得提取的胞外多糖粗品的糖含量为19.58 μg/mL,并用4 mol/L的硫酸完全水解,硅胶G薄层层析,甲醇-氯仿(1:1,体积比）展层,苯胺-二苯胺-磷酸显色,表明其组成成分可能为D-甘露糖、D-半乳糖和D-葡萄糖。该菌株所产的胞外多糖具有提高结皮能力和防沙保水作用,为利用微生物治沙提供参考和种质资源。     

Structure and Dynamics of Exopolymers in an Intertidal Diatom Biofilm

Diatom biofilms growing at the surface of the intertidal mudflat of Marennes Oléron, France, were incubated for 48 h in the laboratory under simulated conditions of high- and low tide (immersed and emersed in seawater) and day and night (illuminated or dark conditions). The biofilms were subsequently sampled using the cryolander technique, without disturbing the structure. The samples were kept in liquid nitrogen until they were transferred to the cooled stage of a field-emission cryo-scanning electron microscope, which was used to study the structural relationships between the sediment particles, the diatoms and the different types of extracellular polymeric substances (EPS) produced by these organisms. The diatoms were most abundant at the sediment surface when incubated in the light under emersed conditions. In the dark or when immersed, the diatoms migrated into the sediment. In the light, the diatoms were coated with EPS, while this was not the case when incubated in the dark. When immersed, the sediment surface appeared smooth as the result of the deposition of mud. Under emersed conditions, the coarser silt grains were prominently present. These grains were wrapped with organic matter and bound together through threads of EPS. This was the case both in light and in dark incubated sediment. It is proposed that this latter type of EPS contributes to the increased erosion threshold of intertidal mudflats colonized by biofilms of diatoms.     

钝顶螺旋藻表面微观形貌的原子力显微镜研究

该文应用原子力显微镜(AFM)纳米级的分辨率对钝顶螺旋藻(Spirulina platensis)表面微观形貌进行了研究,获得了扫描范围为5.000×5.000μm、1.000×1.000μm和400.0×400.0nm三组清晰、稳定的图像,并对其进行了线性分析。结果表明:螺旋藻表面由紧密且无序堆积的突起结构组成,其高度小于20nm;突起结构高度从3nm~15nm不等,平均高度约为8~9nm。此法用于生物体表面,操作简单、快速、灵敏度好且样品无损伤,结果令人满意。     

Measurement of the size and structure of natural aquatic colloids in an urbanised watershed by atomic force microscopy

Atomic force microscopy (AFM) in tapping mode was used to determine the conformation of humic substances and aquatic colloids from rivers in an urban catchment in the West Midlands, U.K. Humic macromolecules were shown to have a size of about 1–3 nm in agreement with the literature, indicating that the preparation methods and the AFM were both performing satisfactorily. Three types of natural aquatic colloids were observed by AFM. Firstly, a surface coating about 1–5 nm thick, likely composed of organic and oxide material flattened by drying and interaction with the AFM tip. Secondly, small irregular, globular material between 1 and 70 nm in size, again most likely made of oxide and organic material. Lastly, fibrillar material was present which was 1–10 nm in diameter and 10–1000 nm in length. Most likely this material was microbially produced (muco-) polysaccharides. Size distributions of colloids from all samples, regardless of sample site and sample preparation, indicated colloids with a fairly low polydispersity and with particle numbers dominated by material <10 nm.     

Impact of the exopolysaccharides Pel and Psl on the initial adhesion of Pseudomonas aeruginosa to sand

In this study, the impact of the exopolysaccharides Pel and Psl on the cell surface electron donor-electron acceptor (acid-base) properties and adhesion to quartz sand was investigated by using Pseudomonas aeruginosa PAO1 and its isogenic EPS-mutant strains Δpel, Δpsl and Δpel/Δpsl. The microbial adhesion to hydrocarbon (MATH) test and titration results showed that both Pel and Psl contribute to the surface hydrophobicity of the cell. The results of contact angle measurement, however, showed no correlation with the cell surface hydrophobicity measured by the MATH test and the titration method. Packed-bed column experiments indicated that the exopolysaccharides Pel and Psl are involved in the initial cell attachment to the sand surface and the extent of their impact is dependent on the ionic strength (IS) of the solution. Overall, the Δpel/Δpsl double mutant had the lowest adhesion coefficient to sand compared with the wild-type PAO1, the Δpel mutant and the Δpsl mutant. It is hypothesized that in addition to bacterial surface hydrophobicity and DLVO forces, other factors, eg steric repulsion caused by extracellular macromolecules, and cell surface appendages (flagella and pili) also contribute significantly to the interaction between the cell surface and a sand grain.     

原子力显微镜研究小鼠免疫球蛋白G自组装

应用原子力显微镜观察小鼠免疫球蛋白G样品,结果不管是IgG1还是IgG1与IgG2的混合样品,在制样2-3d后,均发现有圆环状聚集区,也有部分圆面状聚集区域,一般环中心有核,核为IgG分子多聚体的再聚集,多聚体中亚基（单体）数目因环而异,在圆环和贺湎状区域外,也有零星分散的聚集体,不参与成环,另外,IgG1和IgG1 IgG2聚集情况有所不同,后者更倾向于形成圆面状聚集,另外,在聚集发生前,亚基已自组装形成各种形状的多聚体,然后多聚体进一步聚集形成各种圆环或圆面状,对免疫球蛋白G先自组装而后聚集的过程,从生物学,物理学角度作了初步解释。     

First-Order Assessment of the Influence of Three EPS and Calcite-Producing Microbes Isolated from a Cemented Sand Site on Soil Shear Strength

Subsurface geotechnical data from a cemented tailings sand site in eastern India indicated that the cementation was at least partially biogenic. Three strains of aerobic soil-residing bacteria from this site exhibited capabilities of producing extracellular polymeric substance, calcite and struvite when grown in minimal mineral salt media. These strains grew easily under a variety of physical, chemical and nutritional conditions. Drained triaxial testing of loose sand samples indicated that they became stronger upon hosting these strains. No details on EPS and calcite production of these isolates and the effects of these products on soil behavior were found in the literature.     

氧化亚铁硫杆菌胞外多聚物在生物浸出中的作用

氧化亚铁硫杆菌(Thiobacillus ferrooxidans,T.f)是一种重要的浸矿微生物。它与矿物的界面作用机理是复杂的,涉及物理化学的和生物化学的参数。本文运用电镜细胞化学方法对氧化亚铁硫杆菌(Thiobacillus ferrooxidans)的胞外多聚物(EPS)的脂类、多糖、蛋白质等生物大分子以及铁离子进行了研究,并探讨了EPS与吸附、生物膜形成的关系以及生物膜在浸矿过程中的作用。     

原子力显微镜定量测定采后蘑菇的表面粗糙度(英文)

蘑菇表面的失水情况是评价采后蘑菇质量的重要指标。我们提出用原子力显微镜定量测定蘑菇表皮的粗糙度来表示表面的皱缩程度,用算术平均粗糙度和平方根粗糙度表示。双孢蘑菇(Agaricus bisporus(Lange)Sing)贮藏前的算术平均粗糙度为(34.033±5.116)nm,经过2d贮藏,在2℃、25℃和动态温度自发气调贮藏下,其算术平均粗糙度分别为(40.139±3.359)nm、(65.356±8.253)nm和(43.670±9280)nm。平方根粗糙度值与算术平均粗糙度值有相似的变化趋势,两者均随贮藏时间的延长和温度的增加而增大。表皮的三维图像直观地表示出水分的蒸发过程,变化趋势符合粗糙度值的变化,特别是在贮藏的早期阶段(0～2d)。由粗糙度分析的结果可以区别不同的贮藏条件表明,原子力显微镜测定的粗糙度指标可有效地表示采后蘑菇的表面失水情况。     

Extracellular polymeric substances (EPS) of microbial aggregates in biological wastewater treatment systems: A review

A review concerning the definition, extraction, characterization, production and functions of extracellular polymeric substances (EPS) of microbial aggregates in biological wastewater treatment reactors is given in this paper. EPS are a complex high-molecular-weight mixture of polymers excreted by microorganisms, produced from cell lysis and adsorbed organic matter from wastewater. They are a major component in microbial aggregates for keeping them together in a three-dimensional matrix. Their characteristics (e.g., adsorption abilities, biodegradability and hydrophilicity/hydrophobicity) and the contents of the main components (e.g., carbohydrates, proteins, humic substances and nucleic acids) in EPS are found to crucially affect the properties of microbial aggregates, such as mass transfer, surface characteristics, adsorption ability, stability, the formation of microbial aggregates etc. However, as EPS are very complex, the knowledge regarding EPS is far from complete and much work is still required to fully understand their precise roles in the biological treatment process.     

原子力显微镜研究UV-B对I型胶原结构的影响

利用原子力显微镜(AFM)成像技术观察胶原蛋白溶液在UV-B照射前后形态的变化,发现UV-B引起胶原纤维交联度的增加,当交联达一定程度后,照射时间的增加对交联度增加的影响不明显。AFM作为一种高分辨的表面分析仪器,为分子生物学领域的研究提供了一种新的手段。是探讨胶原光作用机理直观、有效的方法。