我们承认，从酿名斋孙约束力的细胞表面有用的建议。我们感谢斯内德Wingreen Zemer Gitai有价值的讨论。这项研究是由国家卫生研究院授予P50GM07150，国家科学基金事业奖的PHY - 0844466和Alfred P. Sloan基金会的支持。

<ol><li>卢里亚Beltrani肉汤（LB）培养基中的大肠杆菌细胞生长指数生长期（OD = 0.2-0.4）。 </li><li>增长在50微克/毫升头孢氨苄15分钟诱发丝状增长为辅的LB培养，然后通过离心5次集中的文化。 </li><li>流流室加水稀释成1％的聚乙烯涂层裴盖玻片，孵育5分钟后用清水洗净。 </li><li>流入集中的细胞培养室，3分钟后冲洗，以去除独立的细胞，LB和头孢氨苄（50μg/mL）的混合物。 </li><li>室在37℃，30分钟1小时让贴壁细胞上的光学诱捕仪器安置前的生长。 </li><li>孵化在直径0.5微米的聚苯乙烯珠（刘海实验室）30分钟的水稀释0.1％多聚赖氨酸多聚赖氨酸包被的磁珠。然后洗珠的3倍，并重新悬浮在水中。 </li><li>珠的解决方案由两个因素与头孢氨苄（50μg/mL）LB稀释，并添加到流室。 </li><li>光陷阱一个漂珠，触摸到一个单元格的免费提示。 （我们使用一个疯狂的城市实验室压电阶段控制样品的议案。）当找到一个合适的珠/单元组合，洗磅（50μg/mL）室与头孢氨苄删除独立的珠子。 </li><li>运行自定义编写的LabVIEW程序申请弯曲力，细胞和记录力 - 位移数据。节目详情<ol class="lalpha"><li>校准光栅扫描范围内检测激光束和录制3D PSD电压信号的附加珠探测器响应。 </li><li>确定细胞在显微镜图像的长轴。 </li><li>将细胞在细胞长轴垂直方向的步骤。 </li><li>记录移动的距离从光陷阱和位移。 </li><li>转换位移施加的力，使用以前测量的陷阱刚度和节省尖位移和力文件。 </li></ol></li></ol>成功秘诀：在第8步），需要找到一个定义良好的粘结束​​的细胞。一些细胞只是停留在一个提示，并在其他尖端弯曲力，导致整个细胞旋转，而不是弯曲。找到一个合适的一对是由每个细胞迅速弯曲手使用操纵杆控制阶段的议案。 代表性的成果： <img src="/files/ftp_upload/2012/2012fig1.jpg" alt="图1" /> 图1此图显示了一个单细胞的力-位移数据。这条生产线的斜率是细胞的抗弯刚度。

<ol>
	<li>Janmey, P. A., McCulloch, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+mechanics:+integrating+cell+responses+to+mechanical+stimuli.">Cell mechanics: integrating cell responses to mechanical stimuli.</a> Annu Rev Biomed Eng. 9, 1-34 (2007).</li><li>Morris, D. M., Jensen, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+a+biomechanical+understanding+of+whole+bacterial+cells.">Toward a biomechanical understanding of whole bacterial cells.</a> Annu Rev Biochem. 77, 583-613 (2008).</li></ol>

这里介绍的协议的目的是定量测量细菌细胞的弯曲性能。实验装置可应用于任何杆状细胞可以取得增长filamentously。我们已经成功地使用此设置探头E.抗弯刚度骨架细丝的影响大肠杆菌细胞。同样的技术可用于评估的压力，细胞壁的刚度和其他细胞内的组成部分，在决定细胞的整体抗弯刚度的作用。

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">	
		
		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>cephalexin</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>C4895-5G</td>
<td>&nbsp;</td>
<tr>
<td>polyethylenimine</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>181978-5G</td>
<td>&nbsp;</td>
<tr>
<td>polylysine</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>P8920</td>
<td>&nbsp;</td>
<tr>
<td>0.5-&mu;m-diameter polystyrene beads</td>
<td>&nbsp;</td>
<td>Bangs Laboratory</td>
<td>PS03N</td>
<td>&nbsp;</td>
<tr>
<td>Nano-LP Series nanopositioning system</td>
<td>&nbsp;</td>
<td>Mad City Labs</td>
<td>NanoLP series</td>
<td><a href="http://www.madcitylabs.com/nanolpseries.html">http://www.madcitylabs.com/nanolpseries.html</a></td>
</tr>		</tbody>
		</table>
		</div>

measuring the bending stiffness of bacterial cells using an optical trap

我们制定了一个协议来衡量的丝状杆状细菌的抗弯刚度。应用光学陷阱，一个微小的三维光的春天，高强度的激光束聚焦显微镜的物镜，一个非常小的点时会形成部队。弯曲的单元格，我们首先将活的细菌，化学处理过的盖玻片的。由于这些细胞的生长，细胞中仍然绑定到盖玻片，但不断增长的结束是这个约束的自由。通过诱导药物头孢氨苄丝状增长，我们能够识别细胞在被粘表面的细胞的一端，而另一端仍然是独立的和受弯曲力。通过结合一个多聚赖氨酸涂层珠越来越细胞的一角，一个弯曲的力量，然后应用与光学陷阱。珠的力量和位移记录和细胞的抗弯刚度是这种关系的斜率。

Watch this Scientific Journal Video about Measuring the Bending Stiffness of Bacterial Cells Using an Optical Trap at JoVE.com

Measuring the Bending Stiffness of Bacterial Cells Using an Optical Trap

我们提出了一个封面防滑表面附有一个光学陷阱来衡量细胞的抗弯刚度弯曲的丝状细菌细胞的协议。

测量细菌细胞的抗弯刚度，使用光学陷阱

We developed a protocol to measure the bending rigidity of filamentous rod-shaped bacteria. Forces are applied with an optical trap, a microscopic ...

measuring-bending-stiffness-bacterial-cells-using-an-optical

Research

JoVE Journal

Biology

12.0K 次观看.  Princeton University. 我们提出了一个封面防滑表面附有一个光学陷阱来衡量细胞的抗弯刚度弯曲的丝状细菌细胞的协议。

视频: Measuring the Bending Stiffness of Bacterial Cells Using an Optical Trap

Proper Care and Cleaning of the Microscope

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a microscope causes reduction in contrast and resolution. DIC is especially sensitive to contamination and scratches on the lens surfaces. This protocol details the procedure for keeping the microscope clean.

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a microscope causes reduction in contrast and resolution. DIC is especially sensitive to contamination and scratches on the lens surfaces. This protocol details the procedure for keeping the microscope clean.

适当的照顾和清洁的显微镜

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a ...

科研

生物学

Major Components of the Light Microscope

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for different applications, and how it should be maintained as required to obtain maximum image-forming capacity and resolution. The components of the microscope are described in detail here.

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for different applications, and how it should be maintained as required to obtain maximum image-forming capacity and resolution. The components of the microscope are described in detail here.

光镜下的主要组成部分

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for ...

Electron Cryotomography of Bacterial Cells

While much is already known about the basic metabolism of bacterial cells, many fundamental questions are still surprisingly unanswered, including for instance how they generate and maintain specific cell shapes, establish polarity, segregate their genomes, and divide. In order to understand these phenomena, imaging technologies are needed that bridge the resolution gap between fluorescence light microscopy and higher-resolution methods such as X-ray crystallography and NMR spectroscopy.
Electron cryotomography (ECT) is an emerging technology that does just this, allowing the ultrastructure of cells to be visualized in a near-native state, in three dimensions (3D), with "macromolecular" resolution (~4nm).1, 2 In ECT, cells are imaged in a vitreous, "frozen-hydrated" state in a cryo transmission electron microscope (cryoTEM) at low temperature (&lt; -180&deg;C). For slender cells (up to ~500 nm in thickness3), intact cells are plunge-frozen within media across EM grids in cryogens such as ethane or ethane/propane mixtures. Thicker cells and biofilms can also be imaged in a vitreous state by first "high-pressure freezing" and then, "cryo-sectioning" them. A series of two-dimensional projection images are then collected through the sample as it is incrementally tilted along one or two axes. A three-dimensional reconstruction, or "tomogram" can then be calculated from the images. While ECT requires expensive instrumentation, in recent years, it has been used in a few labs to reveal the structures of various external appendages, the structures of different cell envelopes, the positions and structures of cytoskeletal filaments, and the locations and architectures of large macromolecular assemblies such as flagellar motors, internal compartments and chemoreceptor arrays.1, 2
In this video article we illustrate how to image cells with ECT, including the processes of sample preparation, data collection, tomogram reconstruction, and interpretation of the results through segmentation and in some cases correlation with light microscopy.

We illustrate here how to use electron cryotomography (ECT) to study the ultrastructure of bacterial cells in near-native states, to "macromolecular" (~4 nm) resolution.

细菌细胞的电子Cryotomography

While much is already known about the basic metabolism of bacterial cells, many fundamental questions are still surprisingly unanswered, including for ...

Studying the Effects of Matrix Stiffness on Cellular Function using Acrylamide-based Hydrogels

Tissue stiffness is an important determinant of cellular function, and changes in tissue stiffness are commonly associated with fibrosis, cancer and cardiovascular disease1-11. Traditional cell biological approaches to studying cellular function involve culturing cells on a rigid substratum (plastic dishes or glass coverslips) which cannot account for the effect of an elastic ECM or the variations in ECM stiffness between tissues. To model in vivo tissue compliance conditions in vitro, we and others use ECM-coated hydrogels. In our laboratory, the hydrogels are based on polyacrylamide which can mimic the range of tissue compliances seen biologically12. "Reactive" cover slips are generated by incubation with NaOH followed by addition of 3-APTMS. Glutaraldehyde is used to cross-link the 3-APTMS and the polyacrylamide gel. A solution of acrylamide (AC), bis-acrylamide (Bis-AC) and ammonium persulfate is used for the polymerization of the hydrogel. N-hydroxysuccinimide (NHS) is incorporated into the AC solution to crosslink ECM protein to the hydrogel. Following polymerization of the hydrogel, the gel surface is coated with an ECM protein of choice such as fibronectin, vitronectin, collagen, etc.
The stiffness of a hydrogel can be determined by rheology or atomic force microscopy (AFM) and adjusted by varying the percentage of AC and/or bis-AC in the solution12. In this manner, substratum stiffness can be matched to the stiffness of biological tissues which can also be quantified using rheology or AFM. Cells can then be seeded on these hydrogels and cultured based upon the experimental conditions required. Imaging of the cells and their recovery for molecular analysis is straightforward. For this article, we define soft substrata as those having elastic moduli (E) &lt;3000 Pascal and stiff substrata/tissues as those with E &gt;20,000 Pascal.

The effect of substrata stiffness on cellular function can be modeled in vitro using polyacrylamide hydrogels of varying compliances.

使用丙烯酰胺水凝胶的细胞功能的研究矩阵刚度的影响

Tissue stiffness is an important determinant of cellular function, and changes in tissue stiffness are commonly associated with fibrosis, cancer and ...

An Assay for Measuring the Activity of Escherichia coli Inducible Lysine Decarboxyase

Escherichia coli is an enteric bacterium that is capable of growing over a wide range of pH values (pH 5 - 9)1 and, incredibly, is able to survive extreme acid stresses including passage through the mammalian stomach where the pH can fall to as low as pH 1 - 22. To enable such a broad range of acidic pH survival, E. coli possesses four different inducible amino acid decarboxylases that decarboxylate their substrate amino acids in a proton-dependent manner thus raising the internal pH. The decarboxylases include the glutamic acid decarboxylases GadA and GadB3, the arginine decarboxylase AdiA4, the lysine decarboxylase LdcI5, 6 and the ornithine decarboxylase SpeF7. All of these enzymes utilize pyridoxal-5'-phospate as a co-factor8 and function together with inner-membrane substrate-product antiporters that remove decarboxylation products to the external medium in exchange for fresh substrate2. In the case of LdcI, the lysine-cadaverine antiporter is called CadB. Recently, we determined the X-ray crystal structure of LdcI to 2.0 &#197;, and we discovered a novel small-molecule bound to LdcI the stringent response regulator guanosine 5'-diphosphate,3'-diphosphate (ppGpp) 14. The stringent response occurs when exponentially growing cells experience nutrient deprivation or one of a number of other stresses9. As a result, cells produce ppGpp which leads to a signaling cascade culminating in the shift from exponential growth to stationary phase growth10. We have demonstrated that ppGpp is a specific inhibitor of LdcI 14. Here we describe the lysine decarboxylase assay, modified from the assay developed by Phan et al.11, that we have used to determine the activity of LdcI and the effect of pppGpp/ppGpp on that activity. The LdcI decarboxylation reaction removes the &alpha;-carboxy group of L-lysine and produces carbon dioxide and the polyamine cadaverine (1,5-diaminopentane)5. L-lysine and cadaverine can be reacted with 2,4,6-trinitrobenzensulfonic acid (TNBS) at high pH to generate N,N'-bistrinitrophenylcadaverine (TNP-cadaverine) and N,N&#8242;-bistrinitrophenyllysine (TNP-lysine), respectively11. The TNP-cadaverine can be separated from the TNP-lysine as the former is soluble in organic solvents such as toluene while the latter is not (See Figure 1). The linear range of the assay was determined empirically using purified cadaverine.

An Assay for Measuring the Activity of Escherichia coli Inducible Lysine Decarboxyase

The activity of the inducible lysine decarboxylase is monitored by reacting the substrate L-lysine and the product cadaverine with 2,4,6-trinitrobenzensulfonic acid to form adducts that have differential solubility in toluene.

用于测量的活性测定大肠埃希氏菌诱导赖氨酸Decarboxyase

Escherichia coli is an enteric bacterium that is capable of growing over a wide range of pH values (pH 5 - 9)1 and, incredibly, is able to survive extreme ...

Measuring the Kinetics of mRNA Transcription in Single Living Cells

The transcriptional activity of RNA polymerase II (Pol II) is a dynamic process and therefore measuring the kinetics of the transcriptional process in vivo is of importance. Pol II kinetics have been measured using biochemical or molecular methods.1-3 In recent years, with the development of new visualization methods, it has become possible to follow transcription as it occurs in real time in single living cells.4 Herein we describe how to perform analysis of Pol II elongation kinetics on a specific gene in living cells.5, 6 Using a cell line in which a specific gene locus (DNA), its mRNA product, and the final protein product can be fluorescently labeled and visualized in vivo, it is possible to detect the actual transcription of mRNAs on the gene of interest.7, 8 The mRNA is fluorescently tagged using the MS2 system for tagging mRNAs in vivo, where the 3'UTR of the mRNA transcripts contain 24 MS2 stem-loop repeats, which provide highly specific binding sites for the YFP-MS2 coat protein that labels the mRNA as it is transcribed.9 To monitor the kinetics of transcription we use the Fluorescence Recovery After Photobleaching (FRAP) method. By photobleaching the YFP-MS2-tagged nascent transcripts at the site of transcription and then following the recovery of this signal over time, we obtain the synthesis rate of the newly made mRNAs.5 In other words, YFP-MS2 fluorescence recovery reflects the generation of new MS2 stem-loops in the nascent transcripts and their binding by fluorescent free YFP-MS2 molecules entering from the surrounding nucleoplasm. The FRAP recovery curves are then analyzed using mathematical mechanistic models formalized by a series of differential equations, in order to retrieve the kinetic time parameters of transcription.

RNA polymerase II transcriptional kinetics are measured on specific genes in living cells. mRNAs transcribed from the gene of interest are fluorescently tagged and using Fluorescence Recovery After Photobleaching (FRAP) the in vivo kinetics of transcriptional elongation are obtained.

测量单个活细胞中的mRNA转录的动力学

The transcriptional activity of RNA polymerase II (Pol II) is a dynamic process and therefore measuring the kinetics of the transcriptional process in ...

Measuring the Effects of Bacteria on C. Elegans Behavior Using an Egg Retention Assay

C. elegans egg-laying behavior is affected by environmental cues such as osmolarity1 and vibration2. In the total absence of food C. elegans also cease egg-laying and retain fertilized eggs in their uterus3. However, the effect of different sources of food, especially pathogenic bacteria and particularly Enterococcus faecalis, on egg-laying
	behavior is not well characterized. The egg-in-worm (EIW) assay is a useful tool to quantify the effects of different types of bacteria, in this case E. faecalis, on egg- laying behavior.
	
	EIW assays involve counting the number of eggs retained in the uterus of C. elegans4. The EIW assay involves bleaching staged, gravid adult C. elegans to remove the cuticle and separate the retained eggs from the animal. Prior to bleaching, worms are exposed to bacteria (or any type of environmental cue) for a fixed period of time. After bleaching, one is very easily able to count the number of eggs retained inside the uterus of the worms. In this assay, a quantifiable increase in egg retention after E. faecalis exposure can be easily measured. The EIW assay is a behavioral assay that may be used to screen for potentially pathogenic bacteria or the presence of environmental toxins. In addition, the EIW assay may be a tool to screen for drugs that affect neurotransmitter signaling since egg-laying behavior is modulated by neurotransmitters such as serotonin and acetylcholine5-9.

Measuring the Effects of Bacteria on C. Elegans Behavior Using an Egg Retention Assay

An egg-in-worm (EIW) assay is a useful method to quantify egg-laying behavior. Alterations in egg laying can be a behavioral response of the model organism Caenorhabditis elegans to potentially harmful environmental substances such as those produced by pathogenic bacteria.

测量细菌的影响<em&gt; C。线虫</em&gt;行为使用一个鸡蛋保留含量

C. elegans egg-laying behavior is  affected by environmental cues such as osmolarity1 and  vibration2. In the total absence of food C. elegans also cease ...

Measuring the Osmotic Water Permeability Coefficient (Pf) of Spherical Cells: Isolated Plant Protoplasts as an Example

Studying AQP regulation mechanisms is crucial for the understanding of water relations at both the cellular and the whole plant levels. Presented here is a simple and very efficient method for the determination of the osmotic water permeability coefficient (Pf) in plant protoplasts, applicable in principle also to other spherical cells such as frog oocytes. The first step of the assay is the isolation of protoplasts from the plant tissue of interest by enzymatic digestion into a chamber with an appropriate isotonic solution. The second step consists of an osmotic challenge assay: protoplasts immobilized on the bottom of the chamber are submitted to a constant perfusion starting with an isotonic solution and followed by a hypotonic solution. The cell swelling is video recorded. In the third step, the images are processed offline to yield volume changes, and the time course of the volume changes is correlated with the time course of the change in osmolarity of the chamber perfusion medium, using a curve fitting procedure written in Matlab (the &#8216;PfFit&#8217;), to yield Pf.

Measuring the Osmotic Water Permeability Coefficient Pf of Spherical Cells: Isolated Plant Protoplasts as an Example

Measuring the osmotic water permeability coefficient (Pf) of cells can help understand the regulatory mechanisms of aquaporins (AQPs). Pf determination in spherical plant cell protoplasts presented here involves protoplasts isolation and numerical analysis of their initial rate of volume change as a result of an osmotic challenge during constant bath perfusion.

测量渗透水渗透系数（P<sub&gt; F</sub&gt;）球形细胞：隔离植物原生质体为例。

Studying AQP regulation mechanisms is crucial for the understanding of water relations at both the cellular and the whole plant levels. Presented here is ...

Sequential Application of Glass Coverslips to Assess the Compressive Stiffness of the Mouse Lens: Strain and Morphometric Analyses

The eye lens is a transparent organ that refracts and focuses light to form a clear image on the retina. In humans, ciliary muscles contract to deform the lens, leading to an increase in the lens&#39; optical power to focus on nearby objects, a process known as accommodation. Age-related changes in lens stiffness have been linked to presbyopia, a reduction in the lens&#39; ability to accommodate, and, by extension, the need for reading glasses. Even though mouse lenses do not accommodate or develop presbyopia, mouse models can provide an invaluable genetic tool for understanding lens pathologies, and the accelerated aging observed in mice enables the study of age-related changes in the lens. This protocol demonstrates a simple, precise, and cost-effective method for determining mouse lens stiffness, using glass coverslips to apply sequentially increasing compressive loads onto the lens. Representative data confirm that mouse lenses become stiffer with age, like human lenses. This method is highly reproducible and can potentially be scaled up to mechanically test lenses from larger animals.

Age-related increases in eye lens stiffness are linked to presbyopia. This protocol describes a simple, cost-effective method for measuring mouse lens stiffness. Mouse lenses, like human lenses, become stiffer with age. This method is precise and can be adapted for lenses from larger animals.

盖玻片序贯应用评估鼠标透镜的抗压刚度：应变和形态分析

The eye lens is a transparent organ that refracts and focuses light to form a clear image on the retina. In humans, ciliary muscles contract to deform the ...

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a versatile analytical tool for characterizing viscoelastic mechanical properties for a variety of materials ranging from hard (plastic, glass, metal, etc.) surfaces to cells on any substrate. It has been widely used to measure the stiffness of cells, but less frequently used to measure the stiffness of aortas. In this paper, we will describe the procedures for using AFM in contact mode to measure the ex vivo elastic modulus of unloaded mouse arteries. We describe our procedure for isolation of mouse aortas, and then provide detailed information for the AFM analysis. This includes step-by-step instructions for alignment of the laser beam, calibration of the spring constant and deflection sensitivity of the AFM probe, and acquisition of force curves. We also provide a detailed protocol for data analysis of the force curves.

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

We present detailed protocols for isolation of aortas from mouse and measurement of their elastic modulus using atomic force microscopy.

测量的刚度<em&gt;离体</em&gt;鼠标主动脉用原子力显微镜

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a ...