This study was financially supported by the Korean Ministry of Science, ICT and Future Planning (Intelligent Synthetic Biology Center program 2012M3A6A8054887). P. Kim was supported by a fellowship from the Catholic University of Korea (2015).

1.设备的准备<ol><li>得到恒化器罐子（150-250毫升）或含有一个入口的Erlenmeyer烧瓶（250ml）和一出口。用硅管允许10-100毫升/小时的流速连接的端口。任选地，使用空气通气口，出气口，和温度控制的水的入口和出口端口。 </li><li>获得适合的恒化器罐子提供用于搅拌和温度控制装置（或使用旋转式摇床）。 </li><li>以提供新鲜培养基，并收集培养获得两个蠕动泵。 </li><li>得到含有介质出口和一个吸入口的储存罐（10-20升）。 </li><li>获得适合于稀释率硅管（ 即 ，ID0.8毫米，流量范围0.06-36毫升/分钟; L / S 13管）。 </li></ol> 2.中型准备和灭菌<ol><li>初始介质<ol><li>溶解0.3克葡萄糖，0.08克NH 4氯，0.05克氯化钠，0.75克Na 2 HPO 4·2H 2 O，和0.3g KH 2 PO 4在90ml蒸馏水（DW）以恒化器罐子。 </li><li>密封罐子恒用夹子管子一起。不密封该通气孔。 </li><li>消毒在高压釜中的恒化器罐子在121℃下进行15分钟。灭菌后，在室温下储存的恒化器罐子。 </li><li>溶解0.02克用MgSO 4·7H 2 O 0.01克CaCl 2，并在10ml DW（溶液A）0.1毫克硫胺素。 </li><li>过滤溶液A使用注射器和一个预先灭菌的注射器过滤器（0.45微米孔径过滤器）。 </li><li>加入溶液A滤液于恒罐子。 </li></ol></li><li>中等压力<ol><li>溶解30克葡萄糖，将8g 氯化铵 ，5克氯化钠，75克Na 2 HPO 4·2H 2 O，将30g KH 2 PO 4，和300克琥珀酸二钠六水合物（钠2·琥珀酸盐·6H &lt;子&gt; 2 O;在这个实验中使用的应激）在9.9大号DW在贮罐。 </li><li>密封罐藏用夹子管子一起。不密封该通气孔。 </li><li>消毒在高压釜中贮存罐在121℃下15分钟。灭菌后，在室温下储存罐。 </li><li>溶解2克用MgSO 4·7H 2 O，1个克CaCl 2，并在100ml DW（溶液A）10毫克硫胺素。 </li><li>过滤溶液A用注射器和一个预先灭菌的注射器过滤器（0.45微米孔径过滤器）。 </li><li>加入溶液A滤液对储层罐子。 </li><li>无菌连接无菌硅管的水库罐子，装上蠕动泵。 </li></ol></li><li>高应力中<ol><li>制备培养基如2.2节，但与压力源的一个更大的浓度（ 即 ，3-5克/升的琥珀酸适应更高）。 注:该协议是适应应力日在可以经由介质递送。在物理应激如温度，搅拌，或照明的情况下，栽培应相应地设计。 </li></ol></li></ol> 3.初始培养<ol><li>接种野生型大肠杆菌的单个菌落大肠杆菌在含有4毫升起始培养基的15毫升试管中。 </li><li>孵育试管在振荡培养箱中于37℃12小时和220的转速。 </li><li>无菌转移1毫升预培养到恒罐子。 </li><li>孵育恒化器罐子，6小时提供用于充气（空气50ml /分钟）和搅拌（200rpm）下，在37℃下。 </li></ol> 4.适应压力<ol><li>无菌地连接来自泵至恒化器罐子的硅管的端部。 </li><li>启动出口泵（10毫升/小时或更高），并收集培养。 注意:培养应该在指数期，典型地初始培养后4-8小时。 </li><li>通道ECK从出口管培养物的光密度（600nm处）。 </li><li>启动入口泵（10毫升/小时，相当于0.1小时-1的稀释速率）。 </li><li>从出口管每24小时检查在600nm培养物的光密度。 </li><li>操作恒为96小时（9.6倍周转）以上。如果光密度是稳定的，交换包含高应力介质贮存器。如果光学密度低于0.2时，停止进料口泵6小时。重新启动进口泵，检查光密度超过0.2。 </li><li>逐渐改变到含有较高压力源浓度的储增加应激物的浓度。 </li><li>采取适于培养的样品时，它达到一个里程碑（ 例如 ，适于至100克/升琥珀酸应力应变），并存储用于进一步的基因组的分析。 </li><li>样品存储，用无菌80％甘油soluti混合培养样品（0.5毫升）中上（0.5毫升），并将其存储在-80℃。 注意:如果该微生物获取期间ALE过程降解应激的能力，在发酵罐的压力源的浓度是不一样的，在新鲜的贮存器。 </li></ol>应力 - 应变适应5.单菌落分离<ol><li>制备含有相同压力源，并在介质的相同浓度的琼脂平板培养基（1.6％琼脂）。 </li><li>板从恒化器的出口培养（0.1毫升）中，并在37°C孵育16小时。 </li><li>使用无菌牙签挑从板单菌落并且在含有相同应激15毫升试管，并在相同的培养基中的浓度如在恒化器接种他们，孵育6小时。 </li><li>传送1毫升培养液中成含有50毫升培养基的250毫升锥形瓶中。收获将0.5ml培养液的每1小时，并测量在600nm的OD值。比较适应strai的增长速度n至给定的压力源的野生型菌株的。 </li></ol>

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	<li>Rando, O. J., Verstrepen, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Timescales+of+genetic+and+epigenetic+inheritance.">Timescales of genetic and epigenetic inheritance.</a> Cell. 128, 655-668 (2007).</li><li>Kim, H. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Short-term+differential+adaptation+to+anaerobic+stress+via+genomic+mutations+by+Escherichia+coli+strains+K-12+and+B+lacking+alcohol+dehydrogenase.">Short-term differential adaptation to anaerobic stress via genomic mutations by Escherichia coli strains K-12 and B lacking alcohol dehydrogenase.</a> Front Microbiol. 5, 476 (2014).</li><li>Mendizabal, I., Keller, T. E., Zeng, J., Yi, S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epigenetics+and+evolution.">Epigenetics and evolution.</a> Integr Comp Biol. 54, 31-42 (2014).</li><li>Lee, J. Y., Seo, J., Kim, E. S., Lee, H. S., Kim, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adaptive+evolution+of+Corynebacterium+glutamicum+resistant+to+oxidative+stress+and+its+global+gene+expression+profiling.">Adaptive evolution of Corynebacterium glutamicum resistant to oxidative stress and its global gene expression profiling.</a> Biotechnol Lett. 35, 709-717 (2013).</li><li>Lee, J. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Artificial+oxidative+stress-tolerant+Corynebacterium+glutamicum.">Artificial oxidative stress-tolerant Corynebacterium glutamicum.</a> AMB Express. 4, 15 (2014).</li><li>Narang, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+steady+states+of+microbial+growth+on+mixtures+of+substitutable+substrates+in+a+chemostat.">The steady states of microbial growth on mixtures of substitutable substrates in a chemostat.</a> J Theor Biol. 190, 241-261 (1998).</li><li>Kwon, Y. D., Kim, S., Lee, S. Y., Kim, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+continuous+adaptation+of+Escherichia+coli+to+high+succinate+stress+and+transcriptome+analysis+of+the+tolerant+strain.">Long-term continuous adaptation of Escherichia coli to high succinate stress and transcriptome analysis of the tolerant strain.</a> J Biosci Bioeng. 111, 26-30 (2011).</li><li>Barrick, J. E., Lenski, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome+dynamics+during+experimental+evolution.">Genome dynamics during experimental evolution.</a> Nat Rev Genet. 14, 827-839 (2013).</li><li>Li, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Sequence+Alignment/Map+format+and+SAMtools.">The Sequence Alignment/Map format and SAMtools.</a> Bioinformatics. 25, 2078-2079 (2009).</li><li>McKenna, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Genome+Analysis+Toolkit:+a+MapReduce+framework+for+analyzing+next-generation+DNA+sequencing+data.">The Genome Analysis Toolkit: a MapReduce framework for analyzing next-generation DNA sequencing data.</a> Genome Res. 20, 1297-1303 (2010).</li><li>Deatherage, D. E., Barrick, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+mutations+in+laboratory-evolved+microbes+from+next-generation+sequencing+data+using+breseq.">Identification of mutations in laboratory-evolved microbes from next-generation sequencing data using breseq.</a> Methods Mol Biol. 1151, 165-188 (2014).</li></ol>

The authors have nothing to disclose.

微生物能够适应，因为他们的速度快速增长和遗传多样性几乎所有的环境。自适应实验室进化使微生物设计条件，这提供了选择个体生物窝藏自发突变是在给定的条件下有利的方式下发展。 恒化器的技术是用于实现比转移技术人工驱动进化原因如下更健壮:（a）一种稳定的环境 - 因为传输技术基于分批培养物无论是在固体或在液体介质中，该细胞的环境批次期间变化文化而恒...

微生物可以生存和适应不同的环境。在严峻的压力，可以通过随机的基因组突变和随后的正选择1-3取得有益的表型发生调整。因此，微生物细胞可以通过改变代谢或调控网络对于最佳生长，这被称为"自适应进化"适应。最近的重要微生物的倾向，比如超级细菌爆发和强大的微生物菌种的发生，关系非常密切的压力条件下的适应性进化。下定义的实验室条件下，我们能够研究分子进化的机制和甚至控制各种应用微生物进化的方向。与多细胞生物，单细胞生物是非常适合自适应进化实验室（ALE），原因如下:他们很快再生，他们认为大量的人口，而且很容易创建和维护坎ogeneous环境。随着DNA测序技术和高通量技术最新进展相结合，ALE允许对基因组的变化，导致系统性监管政策的变化直接观察。突变动力学和人口的多样性也观察到。遗传工程策略可以从ALE菌株4,5的分析来确定。 恒化器培养是用于获得稳态细胞和发酵过程6提高生产率的方法。新鲜培养基，并将该过程（后者包括介质和生物量）中培养液收获。长期培养恒然而，改变了文化的稳态生产力和文化（ 图1a）期间带来的自发突变和选择的积累。在各种选择压力（压力），突变的积累被提高。应力的长期逐渐增加<html>恒化器提供了用于对给定的压力工作的突变，如温度，pH，渗透压，营养饥饿，氧化，有毒最终产品等菌落转移从液体介质中的固体培养基和串行传输（重复的连续选择分批培养），也让研究人员获得进化微生物（ 图1b和1c）。虽然恒化培养需要复杂的方法中，分集的池（复制和人口规模的数目）比由菌落转移和串行传输技术获得更高。稳定的压力接触到单个细胞和培养恒（稳态）进行比较，以一批以文化​​为基础的技术ALE其他福利过程中的细胞状态下降的变化。经受高琥珀酸条件大肠杆菌应激诱导ALE这篇文章中介绍。 尔斯/ ftp_upload / 54446 / 54446fig1.jpg"/&gt; 图1:自适应进化实验室方法 （A）恒化。 （B）串行传送; （C）菌落转移。顶部图说明为ALE方法的概念，底部数字说明ALE期间增长了细胞的数量。 <a href="https://www.jove.com/files/ftp_upload/54446/54446fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a>

<table><tbody><tr><td>Mini-chemostat fermentor</td><td>Biotron Inc.</td><td>-</td><td>manufactured by special order</td></tr><tr><td>silicon tubing</td><td>Cole-Parmer</td><td>Masterflex L/S 13</td><td>tubing size can be varied depending on the dilution rate and the size of fermentor jar.</td></tr><tr><td>reservoir jar</td><td>Bellco</td><td>Media storage bottle</td><td>20 L</td></tr><tr><td>chemicals</td><td>Sigma-Aldrich</td><td>-</td><td>reagent grade</td></tr><tr><td>glucose</td><td>Sigma-Aldrich</td><td>G5767</td><td>ACS reagent</td></tr><tr><td>NH&lt;sub&gt;4&lt;/sub&gt;Cl</td><td>Sigma-Aldrich</td><td>A9434</td><td>for molecular biology, suitable for cell culture, &amp;ge;99.5%</td></tr><tr><td>NaCl</td><td>Sigma-Aldrich</td><td>746398</td><td>ACS reagent, &amp;ge;99%</td></tr><tr><td>Na&lt;sub&gt;2&lt;/sub&gt;HPO&lt;sub&gt;4&lt;/sub&gt;&amp;middot;2H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Sigma-Aldrich</td><td>4272</td><td>98.5-101%</td></tr><tr><td>KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>795488</td><td>ACS reagent, &amp;ge;99%</td></tr><tr><td>MgSO&lt;sub&gt;4&lt;/sub&gt;&amp;middot;7H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Sigma-Aldrich</td><td>230391</td><td>ACS reagent, &amp;ge;98%</td></tr><tr><td>CaCl&lt;sub&gt;2&lt;/sub&gt;</td><td>Sigma-Aldrich</td><td>793639</td><td>ACS reagent, &amp;ge;96%</td></tr><tr><td>thiamine&amp;middot;HCl</td><td>Sigma-Aldrich</td><td>T4625</td><td>reagent grade, &amp;ge;99%</td></tr><tr><td>Na&lt;sub&gt;2&lt;/sub&gt;&amp;middot;succinate&amp;middot;6H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Sigma-Aldrich</td><td>S2378</td><td>ReagentPlus, &amp;ge;99%</td></tr></tbody></table>

procedure for adaptive laboratory evolution of microorganisms using a chemostat

Natural evolution involves genetic diversity such as environmental change and a selection between small populations. Adaptive laboratory evolution (ALE) refers to the experimental situation in which evolution is observed using living organisms under controlled conditions and stressors; organisms are thereby artificially forced to make evolutionary changes. Microorganisms are subject to a variety of stressors in the environment and are capable of regulating certain stress-inducible proteins to increase their chances of survival. Naturally occurring spontaneous mutations bring about changes in a microorganism's genome that affect its chances of survival. Long-term exposure to chemostat culture provokes an accumulation of spontaneous mutations and renders the most adaptable strain dominant. Compared to the colony transfer and serial transfer methods, chemostat culture entails the highest number of cell divisions and, therefore, the highest number of diverse populations. Although chemostat culture for ALE requires more complicated culture devices, it is less labor intensive once the operation begins. Comparative genomic and transcriptome analyses of the adapted strain provide evolutionary clues as to how the stressors contribute to mutations that overcome the stress. The goal of the current paper is to bring about accelerated evolution of microorganisms under controlled laboratory conditions.

对于高琥珀酸应力适应，野生型E.大肠杆菌 W3110菌株是一个恒化器培养在D = 0.1小时-1 270天（ 图2）。 <img alt="图2" src="/files/ftp_upload/54446/54446fig2.jpg" /> 图2:E的高琥珀酸压力调适大肠杆菌 W3110采用恒化的文化。细箭头表示在该压力源浓度增加，与时俱进，大胆的箭头表示在该培养物保存的时间。用...

Watch this Scientific Journal Video about Procedure for Adaptive Laboratory Evolution of Microorganisms Using a Chemostat at JoVE.com

使用恒化器进行微生物适应性实验室进化的程序|遗传学 |视频

Procedure for Adaptive Laboratory Evolution of Microorganisms Using a Chemostat

在这里，我们提出了一个协议，以获得使用恒化培养条件下微生物实验室适应性进化。此外，演进的株的基因组分析进行了讨论。

程序的微生物实验室自适应演化的恒化

Natural evolution involves genetic diversity such as environmental change and a selection between small populations. Adaptive laboratory evolution (ALE) ...

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14.2K 次观看.  Korea Research Institute of Bioscience and Biotechnology (KRIBB). 在这里，我们提出了一个协议，以获得使用恒化培养条件下微生物实验室适应性进化。此外，演进的株的基因组分析进行了讨论。 

视频: Procedure for Adaptive Laboratory Evolution of Microorganisms Using a Chemostat

Design and Use of a Low Cost, Automated Morbidostat for Adaptive Evolution of Bacteria Under Antibiotic Drug Selection

We describe a low cost, configurable morbidostat for characterizing the evolutionary pathway of antibiotic resistance. The morbidostat is a bacterial culture device that continuously monitors bacterial growth and dynamically adjusts the drug concentration to constantly challenge the bacteria as they evolve to acquire drug resistance. The device features a working volume of ~10 ml and is fully automated and equipped with optical density measurement and micro-pumps for medium and drug delivery. To validate the platform, we measured the stepwise acquisition of trimethoprim resistance in Escherichia coli MG 1655, and integrated the device with a multiplexed microfluidic platform to investigate cell morphology and antibiotic susceptibility. The approach can be up-scaled to laboratory studies of antibiotic drug resistance, and is extendible to adaptive evolution for strain improvements in metabolic engineering and other bacterial culture experiments.

We describe a low cost, configurable morbidostat that enables the characterization of antibiotic drug resistance by dynamically adjusting the drug concentration. The device can be integrated with a multiplexed microfluidic platform. The approach can be scaled up for laboratory antibiotic drug resistance studies.

设计与低成本的使用，自动Morbidostat细菌的适应性进化在抗生素药物的选择

We describe a low cost, configurable morbidostat for characterizing the evolutionary pathway of antibiotic resistance. The morbidostat is a bacterial ...

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CRISPR/Cas9-mediated Targeted Integration In Vivo Using a Homology-mediated End Joining-based Strategy

As a promising genome editing platform, the CRISPR/Cas9 system has great potential for efficient genetic manipulation, especially for targeted integration of transgenes. However, due to the low efficiency of homologous recombination (HR) and various indel mutations of non-homologous end joining (NHEJ)-based strategies in non-dividing cells, in vivo genome editing remains a great challenge. Here, we describe a homology-mediated end joining (HMEJ)-based CRISPR/Cas9 system for efficient in vivo precise targeted integration. In this system, the targeted genome and the donor vector containing homology arms (~800 bp) flanked by single guide RNA (sgRNA) target sequences are cleaved by CRISPR/Cas9. This HMEJ-based strategy achieves efficient transgene integration in mouse zygotes, as well as in hepatocytes in vivo. Moreover, a HMEJ-based strategy offers an efficient approach for correction of fumarylacetoacetate hydrolase (Fah) mutation in the hepatocytes and rescues Fah-deficiency induced liver failure mice. Taken together, focusing on targeted integration, this HMEJ-based strategy provides a promising tool for a variety of applications, including generation of genetically modified animal models and targeted gene therapies.

CRISPR/Cas9-mediated Targeted Integration In Vivo Using a Homology-mediated End Joining-based Strategy

The clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9 (CRISPR/Cas9) system provides a promising tool for genetic engineering, and opens up the possibility of targeted integration of transgenes. We describe a homology-mediated end joining (HMEJ)-based strategy for efficient DNA targeted integration in vivo and targeted gene therapies using CRISPR/Cas9.

CRISPR/Cas9-mediated 目标集成在体内使用基于同源介导的端接连接策略

As a promising genome editing platform, the CRISPR/Cas9 system has great potential for efficient genetic manipulation, especially for targeted integration ...

Genome-wide Surveillance of Transcription Errors in Eukaryotic Organisms

Accurate transcription is required for the faithful expression of genetic information. Surprisingly though, little is known about the mechanisms that control the fidelity of transcription. To fill this gap in scientific knowledge, we recently optimized the circle-sequencing assay to detect transcription errors throughout the transcriptome of Saccharomyces cerevisiae, Drosophila melanogaster, and Caenorhabditis elegans. This protocol will provide researchers with a powerful new tool to map the landscape of transcription errors in eukaryotic cells so that the mechanisms that control the fidelity of transcription can be elucidated in unprecedented detail.

This protocol provides researchers with a new tool to monitor the fidelity of transcription in multiple model organisms.

全基因组对真核生物转录误差的监测

Accurate transcription is required for the faithful expression of genetic information. Surprisingly though, little is known about the mechanisms that ...

Designing Automated, High-throughput, Continuous Cell Growth Experiments Using eVOLVER

Continuous culture methods enable cells to be grown under quantitatively controlled environmental conditions, and are thus broadly useful for measuring fitness phenotypes and improving our understanding of how genotypes are shaped by selection. Extensive recent efforts to develop and apply niche continuous culture devices have revealed the benefits of conducting new forms of cell culture control. This includes defining custom selection pressures and increasing throughput for studies ranging from long-term experimental evolution to genome-wide library selections and synthetic gene circuit characterization. The eVOLVER platform was recently developed to meet this growing demand: a continuous culture platform with a high degree of scalability, flexibility, and automation. eVOLVER provides a single standardizing platform that can be (re)-configured and scaled with minimal effort to perform many different types of high-throughput or multi-dimensional growth selection experiments. Here, a protocol is presented to provide users of the eVOLVER framework a description for configuring the system to conduct a custom, large-scale continuous growth experiment. Specifically, the protocol guides users on how to program the system to multiplex two selection pressures &#8212; temperature and osmolarity &#8212; across many eVOLVER vials in order to quantify fitness landscapes of Saccharomyces cerevisiae mutants at fine resolution. We show how the device can be configured both programmatically, through its open-source web-based software, and physically, by arranging fluidic and hardware layouts. The process of physically setting up the device, programming the culture routine, monitoring and interacting with the experiment in real-time over the internet, sampling vials for subsequent offline analysis, and post experiment data analysis are detailed. This should serve as a starting point for researchers across diverse disciplines to apply eVOLVER in the design of their own complex and high-throughput cell growth experiments to study and manipulate biological systems.

The eVOLVER framework enables high-throughput continuous microbial culture with high resolution and dynamic control over experimental parameters. This protocol demonstrates how to apply the system to conduct a complex fitness experiment, guiding users on programming automated control over many individual cultures, measuring, collecting, and interacting with experimental data in real-time.

使用 Ever 设计自动化、高通量、连续细胞生长实验

Continuous culture methods enable cells to be grown under quantitatively controlled environmental conditions, and are thus broadly useful for measuring ...

Daily Transfers, Archiving Populations, and Measuring Fitness in the Long-Term Evolution Experiment with Escherichia coli

The Long-Term Evolution Experiment (LTEE) has followed twelve populations of Escherichia coli as they have adapted to a simple laboratory environment for more than 35 years and 77,000 bacterial generations. The setup and procedures used in the LTEE epitomize reliable and reproducible methods for studying microbial evolution. In this protocol, we first describe how the LTEE populations are transferred to fresh medium and cultured each day. Then, we describe how the LTEE populations are regularly checked for possible signs of contamination and archived to provide a permanent frozen "fossil record" for later study. Multiple safeguards included in these procedures are designed to prevent contamination, detect various problems when they occur, and recover from disruptions without appreciably setting back the progress of the experiment. One way that the overall tempo and character of evolutionary changes are monitored in the LTEE is by measuring the competitive fitness of populations and strains from the experiment. We describe how co-culture competition assays are conducted and provide both a spreadsheet and an R package (fitnessR) for calculating relative fitness from the results. Over the course of the LTEE, the behaviors of some populations have changed in interesting ways, and new technologies like whole-genome sequencing have provided additional avenues for investigating how the populations have evolved. We end by discussing how the original LTEE procedures have been updated to accommodate or take advantage of these changes. This protocol will be useful for researchers who use the LTEE as a model system for studying connections between evolution and genetics, molecular biology, systems biology, and ecology. More broadly, the LTEE provides a tried-and-true template for those who are beginning their own evolution experiments with new microbes, environments, and questions.

Daily Transfers, Archiving Populations, and Measuring Fitness in the Long-Term Evolution Experiment with Escherichia coli

This protocol describes how to maintain the Escherichia coli Long-Term Evolution Experiment (LTEE) by performing its daily transfers and periodic freeze-downs and how to conduct competition assays to measure fitness improvements in evolved bacteria. These procedures can serve as a template for researchers starting their own microbial evolution experiments.

大肠杆菌长期进化实验中的每日转移、存档种群和测量适应性

The Long-Term Evolution Experiment (LTEE) has followed twelve populations of Escherichia coli as they have adapted to a simple laboratory environment for ...

Generating Controlled, Dynamic Chemical Landscapes to Study Microbial Behavior

We demonstrate a method for the generation of controlled, dynamic chemical pulses&#8213;where localized chemoattractant becomes suddenly available at the microscale&#8213;to create micro-environments for microbial chemotaxis experiments. To create chemical pulses, we developed a system to introduce amino acid sources near-instantaneously by photolysis of caged amino acids within a polydimethylsiloxane (PDMS) microfluidic chamber containing a bacterial suspension. We applied this method to the chemotactic bacterium, Vibrio ordalii, which can actively climb these dynamic chemical gradients while being tracked by video microscopy. Amino acids, rendered biologically inert (&#39;caged&#39;) by chemical modification with a photoremovable protecting group, are uniformly present in the suspension but not available for consumption until their sudden release, which occurs at user-defined points in time and space by means of a near-UV-A focused LED beam. The number of molecules released in the pulse can be determined by a calibration relationship between exposure time and uncaging fraction, where the absorption spectrum after photolysis is characterized by using UV-Vis spectroscopy. A nanoporous polycarbonate (PCTE) membrane can be integrated into the microfluidic device to allow the continuous removal by flow of the uncaged compounds and the spent media. A strong, irreversible bond between the PCTE membrane and the PDMS microfluidic structure is achieved by coating the membrane with a solution of 3-aminopropyltriethoxysilane (APTES) followed by plasma activation of the surfaces to be bonded. A computer-controlled system can generate user-defined sequences of pulses at different locations and with different intensities, so as to create resource landscapes with prescribed spatial and temporal variability. In each chemical landscape, the dynamics of bacterial movement at the individual scale and their accumulation at the population level can be obtained, thereby allowing the quantification of chemotactic performance and its effects on bacterial aggregations in ecologically relevant environments.

A protocol for the generation of dynamic chemical landscapes by photolysis within microfluidic and millifluidic setups is presented. This methodology is suitable to study diverse biological processes, including the motile behavior, nutrient uptake, or adaptation to chemicals of microorganisms, both at the single cell and population level.

生成受控动态化学景观，研究微生物行为

We demonstrate a method for the generation of controlled, dynamic chemical pulses&#8213;where localized chemoattractant becomes suddenly available at the ...

生物工程

Automated Microbial Cultivation and Adaptive Evolution using Microbial Microdroplet Culture System (MMC)

Conventional microbial cultivation methods usually have cumbersome operations, low throughput, low efficiency, and large consumption of labor and reagents. Moreover, microplate-based high-throughput cultivation methods developed in recent years have poor microbial growth status and experiment parallelization because of their low dissolved oxygen, poor mixture, and severe evaporation and thermal effect. Due to many advantages of micro-droplets, such as small volume, high throughput, and strong controllability, the droplet-based microfluidic technology can overcome these problems, which has been used in many kinds of research of high-throughput microbial cultivation, screening, and evolution. However, most prior studies remain&#160;at the stage of laboratory construction and application. Some key issues, such as high operational requirements, high construction difficulty, and lack of automated integration technology, restrict the wide application of droplet microfluidic technology in microbial research. Here, an automated Microbial Microdroplet Culture system (MMC) was successfully developed based on droplet microfluidic technology, achieving the integration of functions such as inoculation, cultivation, online monitoring, sub-cultivation, sorting, and sampling required by the process of microbial droplet cultivation. In this protocol, wild-type Escherichia coli (E. coli) MG1655 and a methanol-essential E. coli strain (MeSV2.2) were taken as examples to introduce how to use the MMC to conduct automated and relatively high-throughput microbial cultivation and adaptive evolution in detail. This method is easy to operate, consumes less labor and reagents, and has high experimental throughput and good data parallelity, which has great advantages compared with conventional cultivation methods. It provides a low-cost, operation-friendly, and result-reliable experimental platform for scientific researchers to conduct related microbial research.

Automated Microbial Cultivation and Adaptive Evolution using Microbial Microdroplet Culture System MMC

This protocol describes how to use the Microbial Microdroplet Culture system (MMC) to conduct automated microbial cultivation and adaptive evolution. MMC can cultivate and sub-cultivate microorganisms automatically and continuously and monitor online their growth with relatively high throughput and good parallelization, reducing labor and reagent consumption.

使用微生物滴培养系统（MMC）的自动微生物培养和适应性进化

Conventional microbial cultivation methods usually have cumbersome operations, low throughput, low efficiency, and large consumption of labor and ...

The Use of Chemostats in Microbial Systems Biology

Cells regulate their rate of growth in response to signals from the external world. As the cell grows, diverse cellular processes must be coordinated including macromolecular synthesis, metabolism and ultimately, commitment to the cell division cycle. The chemostat, a method of experimentally controlling cell growth rate, provides a powerful means of systematically studying how growth rate impacts cellular processes - including gene expression and metabolism - and the regulatory networks that control the rate of cell growth. When maintained for hundreds of generations chemostats can be used to study adaptive evolution of microbes in environmental conditions that limit cell growth. We describe the principle of chemostat cultures, demonstrate their operation and provide examples of their various applications. Following a period of disuse after their introduction in the middle of the twentieth century, the convergence of genome-scale methodologies with a renewed interest in the regulation of cell growth and the molecular basis of adaptive evolution is stimulating a renaissance in the use of chemostats in biological research.

Cell growth rate is a regulated process and a primary determinant of cell physiology. Continuous culturing using chemostats enables extrinsic control of cell growth rate by nutrient limitation facilitating the study of molecular networks that control cell growth and how those networks evolve to optimize cell growth.

恒化器中微生物系统生物学中的应用

Cells regulate their rate of growth in response to signals from the external world. As the cell grows, diverse cellular processes must be coordinated ...

生物学

Design and Use of Multiplexed Chemostat Arrays

Chemostats are continuous culture systems in which cells are grown in a tightly controlled, chemically constant environment where culture density is constrained by limiting specific nutrients.1,2 Data from chemostats are highly reproducible for the measurement of quantitative phenotypes as they provide a constant growth rate and environment at steady state. For these reasons, chemostats have become useful tools for fine-scale characterization of physiology through analysis of gene expression3-6 and other characteristics of cultures at steady-state equilibrium.7 Long-term experiments in chemostats can highlight specific trajectories that microbial populations adopt during adaptive evolution in a controlled environment. In fact, chemostats have been used for experimental evolution since their invention.8 A common result in evolution experiments is for each biological replicate to acquire a unique repertoire of mutations.9-13 This diversity suggests that there is much left to be discovered by performing evolution experiments with far greater throughput. 
We present here the design and operation of a relatively simple, low cost array of miniature chemostats&mdash;or ministats&mdash;and validate their use in determination of physiology and in evolution experiments with yeast. This approach entails growth of tens of chemostats run off a single multiplexed peristaltic pump. The cultures are maintained at a 20 ml working volume, which is practical for a variety of applications. It is our hope that increasing throughput, decreasing expense, and providing detailed building and operation instructions may also motivate research and industrial application of this design as a general platform for functionally characterizing large numbers of strains, species, and growth parameters, as well as genetic or drug libraries.

We developed and validated a small-footprint array of miniature chemostats built from readily available parts for low cost. Physiological and experimental evolution results were similar to larger volume chemostats. The ministat array provides a compact, inexpensive, and accessible platform for traditional chemostat experiments, functional genomics, and chemical screening applications.

复用的恒化器阵列的设计与应用

Chemostats are continuous culture systems in which cells are grown in a tightly controlled, chemically constant environment where culture density is ...

<meta charset="utf8"></head><body>使用低成本 Thermomixer 进行嗜热体驯化的实验进化方案

Adaptation at the Extremes of Life: Experimental Evolution with the Extremophile Archaeon Sulfolobus acidocaldarius

The archaeon Sulfolobus acidocaldarius has emerged as a promising thermophilic model system. Investigating how thermophiles adapt to changing temperatures is a key requirement, not only for understanding fundamental evolutionary processes but also for developing S. acidocaldarius as a chassis for bioengineering. One major obstacle to conducting experimental evolution with thermophiles is the expense of equipment maintenance and energy usage of traditional incubators for high-temperature growth. To address this challenge, a comprehensive experimental protocol for conducting experimental evolution in S. acidocaldarius is presented, utilizing low-cost and energy-efficient bench-top thermomixers. The protocol involves a batch culture technique with relatively small volumes (1.5 mL), enabling tracking of adaptation in multiple independent lineages. This method is easily scalable through the use of additional thermomixers. Such an approach increases the accessibility of S. acidocaldarius as a model system by reducing both initial investment and ongoing costs associated with experimental investigations. Moreover, the technique is transferable to other microbial systems for exploring adaptation to diverse environmental conditions.

<meta charset="utf8"></head><body>作者聚焦：使用创新技术了解微生物适应，探索嗜热性进化

Here, we present an experimental evolution protocol for adaptation in thermophiles utilizing low-cost, energy-efficient bench-top thermomixers as incubators. The technique is demonstrated through the characterization of temperature adaptation in Sulfolobus acidocaldarius, an archaeon with an optimal growth temperature of 75 &#176;C.

生命极端的适应：极端微生物 Sulfolobus acidocaldarius 的实验进化

The archaeon Sulfolobus acidocaldarius has emerged as a promising thermophilic model system. Investigating how thermophiles adapt to changing temperatures ...