Эта работа была поддержана грантом Национального института здравоохранения GM118085 и частично Фондом Роберта Уэлча (грант F-1811 R.M.H.).

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Выделение и характеристика мутаций супрессоров успешно способствовали выявлению ключевых компонентов системы хемотаксиса35,36,37,а также самого моторного механизма38,39,40. При использов?...

Бактерии используют множество придатков для перемещения и рассеивания в своих экологических нишах1. Подвижность, управляемая жгутителями, является самой быстрой из них, способствуя колонизации благоприятных мест в ответ на сигналы окружающей среды и внося значительный вклад в патогенную способность некоторых видов2,3. Жгутиковые бактерии могут плавать индивидуально в объемной жидкости или роиться как коллектив над полутвердой поверхностью4. Внеклеточные жгутики прикрепляются и приводятся в движение роторными двигателями, встроенными в мембрану, которые используют мощность ионных градиентов для создания крутящегомомента,который вызывает вращение1,2,4,5,6,7,8. В E. coli,чьи двигатели работают с постоянным крутящим моментом9,мощность двигателя может быть классифицирована с точки зрения скорости вращения и переключения ротора между направлениями против часовой стрелки (CCW) и по часовой стрелке (CW). Вращение КНО способствует образованию когерентного жгутикового пучка, который продвигает ячейку вперед (бег), в то время как переходный переключатель в направлении вращения (CW) заставляет пучок разбираться частично или полностьюна 10,а клетка переориентировать свое направление плавания (кувыркаться). Кишечно-кишечное кишечное правило бегает в течение секунды и кувыркается в течение десятой доли секунды. Частота переключения ротора или «кувыркающееся смещение» контролируется сигнальной системой хемотаксиса, в которой трансмембранные хеморецепторы обнаруживают внешние химические сигналы и передают их через фосфорелай жгутиковый двигатель для продления пробегов в ответ на аттрактанты или подавления их в ответ на токсичные химические вещества11,12. Подвижность плавания анализируется в 0,3% мягкого агара.
Во время роения бактерии перемещаются по полутвердой поверхности в виде плотного коллектива, где стаи бактерий текут в непрерывном вихревом движении2,13,14,15. Рои E. coli демонстрируют измененную хемосенсорную физиологию (более низкое смещение падения), более высокие скорости и более высокую толерантность к противомикробным препаратам над клетками, плавающими в объемной жидкости16,17. Рои различаются в своем развертывании множества стратегий, которые помогают движению, включая производство поверхностно-активных добавок, гиперфлагелляцию и удлинение клеток2. Роение дает бактериям конкурентное преимущество как в экологических, так и в клинических условиях18,19,20. Существует две категории роящихся бактерий: умеренные рои, которые могут роиться только на средах, затвердевшие с 0,5-0,8% агара, и надежные рои, которые могут перемещаться по более высоким концентрациям агара21.
Существует множество анализов, чтобы исследовать подвижность плавания и ее регулирование. При нарушении мутаций или условий окружающей среды подвижность сама по себе предлагает сильный выбор для выявления мутаций-супрессоров усиления функции. Эти супрессоры могут быть подлинными ревертантами исходной мутации или псевдо-ревертантами, где вторая мутация восстанавливает функциональность. Такие мутанты могут быть идентифицированы путем секвенирования всего генома (WGS). Альтернативой непредвзятому выбору супрессора является предвзятая стратегия целенаправленного мутагенеза (например, мутагенез ПЦР). Эти методологии часто проливает свет на функцию или экологическую регуляцию аппарата моторики. Если цель состоит в том, чтобы изучить двигательную функцию, то восстановление подвижности дикого типа, измеренное в мягком агари, не обязательно может указывать на восстановление двигательной мощности дикого типа. Анализ клеточного привязки, в котором клетки прикрепляются к стеклянной поверхности одним жгутиком и впоследствии контролируется вращение тела клетки, может быть начальным анализом выбора для оценки двигательного поведения. Хотя в настоящее время доступны более сложные методологии для мониторинга свойств двигателя, требуемая высокоскоростная настройка камер и применение пакетов программного обеспечения для анализа движения ограничивают их широкое использование22,23,24,25. Анализ клеточного привязки требует только, чтобы жгутики были сстрижены, что позволяет прикрепить короткие нити к стеклянному слайду с последующей видеозаписью вращения тела клетки. Хотя зарегистрированные скорости двигателя низки в этом анализе из-за высокой нагрузки, которую тело клетки оказывает на жгутик, этот анализ, тем не менее, способствовал ценному пониманию хемотаксических реакций26,27,28,29и остается действительным инструментом исследования, как обсуждается ниже.
Роевая подвижность ставит перед исследователями другой набор проблем. Выбор супрессоров усиления функции работает только в роях, которые производят обильные поверхностно-активные вещества и роя легко13. Поверхностно-активные непроизводители, такие как E. coli, привередливы в отношении выбора агара, состава среды и влажности окружающей среды2,13,14,21. После того, как условия роения установлены, анализ пересечения границы17 является полезной методологией для опроса о способности роя ориентироваться в новых/суровых условиях. Хотя протоколы, представленные ниже, относятся к E. coli,они могут быть легко адаптированы для применения у других видов.

<table>
	<tbody>
		<tr>
			<td>Reagents</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Bacto Dehydrated Agar</td>
			<td>Fisher Scientific</td>
			<td>DF0140-15-4</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA Disodium Salt, Dihydrate</td>
			<td>Fisher Scientific</td>
			<td>02-002-786</td>
			<td></td>
		</tr>
		<tr>
			<td>Eiken agar</td>
			<td>Eiken Chemical Co. Japan</td>
			<td>E-MJ00</td>
			<td>Essential for E. coli swarming</td>
		</tr>
		<tr>
			<td>Glucose D (+)</td>
			<td>Fisher Scientific</td>
			<td>410955000</td>
			<td></td>
		</tr>
		<tr>
			<td>LB (Lennox) Broth</td>
			<td>Fisher Scientific</td>
			<td>BP1427-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly-L-lysine Solution (0.1%)</td>
			<td>Sigma-Aldrich</td>
			<td>P8920</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium chloride (KCl)</td>
			<td>Fisher Scientific</td>
			<td>18-605-496</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Phosphate monobasic (KH2PO4)</td>
			<td>Fisher Scientific</td>
			<td>BP362-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Phosphate dibasic (K2HPO4)</td>
			<td>Fisher Scientific</td>
			<td>BP363-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride (NaCl)</td>
			<td>Fisher Scientific</td>
			<td>S271-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Materials and Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CellSense microscope imaging software (V. 1.6)</td>
			<td>Olympus</td>
			<td></td>
			<td>Or equivalent software for microscope used</td>
		</tr>
		<tr>
			<td>Electron Microscopy Sciences Scotch 666 Doube Sided Tape</td>
			<td>Fisher</td>
			<td>50-285-28</td>
			<td></td>
		</tr>
		<tr>
			<td>Frosted microscope slides 3x1x1mm</td>
			<td>Fisher</td>
			<td>12-550-343</td>
			<td></td>
		</tr>
		<tr>
			<td>Olympus BX53 microscope</td>
			<td>Olympus</td>
			<td>BX53</td>
			<td>Any upright or inverted phase microscope can be used</td>
		</tr>
		<tr>
			<td>Petri dishes (100 mm diameter)</td>
			<td>Fisher Scientific</td>
			<td>FB0875712</td>
			<td>For soft-agar assays</td>
		</tr>
		<tr>
			<td>Polyethylene Nebulizer Capillary Tubing (0.58mm x 99mm 3.0m)</td>
			<td>Perkin Elmer</td>
			<td>9908265</td>
			<td></td>
		</tr>
		<tr>
			<td>Round Petri Dish with 2 Compartments</td>
			<td>VWR</td>
			<td>89200-944</td>
			<td>For border-crossing assays</td>
		</tr>
		<tr>
			<td>Safety Hypodermic Needles (23G)</td>
			<td>Fisher Scientific</td>
			<td>14-826A</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile Syringe - 1 mL</td>
			<td>Fisher scientific</td>
			<td>14-955-450</td>
			<td></td>
		</tr>
		<tr>
			<td>Task/Tissue wipes</td>
			<td>Fisher scientific</td>
			<td>06-666</td>
			<td>Or equivalent single use tissue wipes</td>
		</tr>
		<tr>
			<td>VWR micro cover-glass 18x18mm</td>
			<td>VWR</td>
			<td>48366205</td>
			<td></td>
		</tr>
		<tr>
			<td>XM10 camera</td>
			<td>Olympus</td>
			<td>XM10</td>
			<td>Or equivalent microscope camera</td>
		</tr>
	</tbody>
</table>

investigating flagella-driven motility in escherichia coli by applying three established techniques in a series

Подвижность имеет решающее значение для выживания и успеха многих видов бактерий. Существует множество методологий для использования подвижности для понимания сигнальных путей, выяснения функции и сборки жгутиков, а также для изучения и понимания моделей движения. Здесь мы демонстрируем сочетание трех из этих методологий. Подвижность в мягком агарове является самой старой, предлагая сильный отбор для выделения мутаций супрессора усиления функции у штаммов с нарушениями подвижности, где подвижность восстанавливается с помощью второй мутации. Метод клеточного троса, впервые использованный для демонстрации вращательной природы жгутикового двигателя, может быть использован для оценки влияния сигнальных эффекторов на скорость двигателя и его способность переключать направление вращения. Анализ «пересечения границы» является более недавним, где плавающие бактерии могут быть подготовлены к переходу в коллективное движение в качестве роя. В сочетании эти протоколы представляют собой систематический и мощный подход к выявлению компонентов механизмов подвижности и характеристике их роли в различных аспектах плавания и роения. Они могут быть легко адаптированы для изучения подвижности у других видов бактерий.

Выделение псевдо-ревертантов в штамме E. coli, подвижность которого нарушается высокими уровнями сигнальной молекулы c-di-GMP, была подробно описана в недавней работе нашей лаборатории34. Этот штамм (JP1442) содержит две мутации: ΔyhjH и ΔycgR. YhjH является наиболее активно?...

Watch this Scientific Journal Video about Investigating Flagella-Driven Motility in Escherichia coli by Applying Three Established Techniques in a Series at JoVE.com

Investigating Flagella-Driven Motility in Escherichia coli by Applying Three Established Techniques in a Series

Многие бактерии используют подвижность, управляемую жгутиками, чтобы ориентироваться в окружающей среде и колонизировать благоприятное окружение как индивидуально, так и коллективно. Здесь показано использование трех установленных методов, которые используют подвижность в качестве инструмента выбора для выявления компонентов / путей, способствующих плаванию и роевой подвижности.

Исследование подвижности жгутиков у кишечной палочки путем применения трех установленных методов в серии

Motility is crucial to the survival and success of many bacterial species. Many methodologies exist to exploit motility to understand signaling pathways, ...

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Investigating Flagella-Driven Motility in Escherichia coli by Applying Three Established Techniques in a Series

7.5K Views.  The University of Texas at Austin. Многие бактерии используют подвижность, управляемую жгутиками, чтобы ориентироваться в окружающей среде и колонизировать благоприятное окружение как индивидуально, так и коллективно. Здесь показано использование трех установленных методов, которые исполь...

Video: Investigating Flagella-Driven Motility in Escherichia coli by Applying Three Established Techniques in a Series

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.

Тест для измерения активности Кишечной палочки Индуцибельной Лизин 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 ...

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes

The protocol presented here is designed to study the activation of the large conductance, voltage- and Ca2+-activated K+ (BK) channels. The protocol may also be used to study the structure-function relationship for other ion channels and neurotransmitter receptors1. BK channels are widely expressed in different tissues and have been implicated in many physiological functions, including regulation of smooth muscle contraction, frequency tuning of inner hair cells and regulation of neurotransmitter release2-6. BK channels are activated by membrane depolarization and by intracellular Ca2+ and Mg2+ 6-9. Therefore, the protocol is designed to control both the membrane voltage and the intracellular solution. In this protocol, messenger RNA of BK channels is injected into Xenopus laevis oocytes (stage V-VI) followed by 2-5 days of incubation at 18&deg;C10-13. Membrane patches that contain single or multiple BK channels are excised with the inside-out configuration using patch clamp techniques10-13. The intracellular side of the patch is perfused with desired solutions during recording so that the channel activation under different conditions can be examined. To summarize, the mRNA of BK channels is injected into Xenopus laevis oocytes to express channel proteins on the oocyte membrane; patch clamp techniques are used to record currents flowing through the channels under controlled voltage and intracellular solutions.

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes

Ionic current of BK channels is recorded using patch clamp techniques. BK channels are expressed in Xenopus oocytes by injecting messenger RNA. The intracellular solution during patch clamp recordings is controlled by a perfusion system.

Зажим Patch и перфузии Методы изучения ионных каналов, выраженные в Xenopus Ооцитов

The protocol presented here is designed to study the activation of the large conductance, voltage- and Ca2+-activated K+ (BK) channels. The protocol may ...

High Throughput Screening of Fungal Endoglucanase Activity in Escherichia coli

Cellulase enzymes (endoglucanases, cellobiohydrolases, and &beta;-glucosidases) hydrolyze cellulose into component sugars, which in turn can be converted into fuel alcohols1. The potential for enzymatic hydrolysis of cellulosic biomass to provide renewable energy has intensified efforts to engineer cellulases for economical fuel production2. Of particular interest are fungal cellulases3-8, which are already being used industrially for foods and textiles processing.
Identifying active variants among a library of mutant cellulases is critical to the engineering process; active mutants can be further tested for improved properties and/or subjected to additional mutagenesis. Efficient engineering of fungal cellulases has been hampered by a lack of genetic tools for native organisms and by difficulties in expressing the enzymes in heterologous hosts. Recently, Morikawa and coworkers developed a method for expressing in E. coli the catalytic domains of endoglucanases from H. jecorina3,9, an important industrial fungus with the capacity to secrete cellulases in large quantities. Functional E. coli expression has also been reported for cellulases from other fungi, including Macrophomina phaseolina10 and Phanerochaete chrysosporium11-12. 
We present a method for high throughput screening of fungal endoglucanase activity in E. coli. (Fig 1) This method uses the common microbial dye Congo Red (CR) to visualize enzymatic degradation of carboxymethyl cellulose (CMC) by cells growing on solid medium. The activity assay requires inexpensive reagents, minimal manipulation, and gives unambiguous results as zones of degradation (&#x201C;halos&#x201D;) at the colony site. Although a quantitative measure of enzymatic activity cannot be determined by this method, we have found that halo size correlates with total enzymatic activity in the cell. Further characterization of individual positive clones will determine , relative protein fitness. 
Traditional bacterial whole cell CMC/CR activity assays13 involve pouring agar containing CMC onto colonies, which is subject to cross-contamination, or incubating cultures in CMC agar wells, which is less amenable to large-scale experimentation. Here we report an improved protocol that modifies existing wash methods14 for cellulase activity: cells grown on CMC agar plates are removed prior to CR staining. Our protocol significantly reduces cross-contamination and is highly scalable, allowing the rapid screening of thousands of clones. In addition to H. jecorina enzymes, we have expressed and screened endoglucanase variants from the Thermoascus aurantiacus and Penicillium decumbens (shown in Figure 2), suggesting that this protocol is applicable to enzymes from a range of organisms.

High Throughput Screening of Fungal Endoglucanase Activity in Escherichia coli

We describe a low cost, high throughput method to screen for fungal endoglucanase activity in E. coli. The method relies on a simple visual readout of substrate degradation, does not require enzyme purification, and is highly scalable. This allows for the rapid screening of large libraries of enzyme variants.

Высокопроизводительного скрининга грибной активность в эндоглюканазы Кишечной палочки</em

Cellulase enzymes (endoglucanases, cellobiohydrolases, and &beta;-glucosidases) hydrolyze cellulose into component sugars, which in turn can be converted ...

Mapping Bacterial Functional Networks and Pathways in Escherichia Coli using Synthetic Genetic Arrays

Phenotypes are determined by a complex series of physical (e.g. protein-protein) and functional (e.g. gene-gene or genetic) interactions (GI)1. While physical interactions can indicate which bacterial proteins are associated as complexes, they do not necessarily reveal pathway-level functional relationships1. GI screens, in which the growth of double mutants bearing two deleted or inactivated genes is measured and compared to the corresponding single mutants, can illuminate epistatic dependencies between loci and hence provide a means to query and discover novel functional relationships2. Large-scale GI maps have been reported for eukaryotic organisms like yeast3-7, but GI information remains sparse for prokaryotes8, which hinders the functional annotation of bacterial genomes. To this end, we and others have developed high-throughput quantitative bacterial GI screening methods9, 10.
Here, we present the key steps required to perform quantitative E. coli Synthetic Genetic Array (eSGA) screening procedure on a genome-scale9, using natural bacterial conjugation and homologous recombination to systemically generate and measure the fitness of large numbers of double mutants in a colony array format. Briefly, a robot is used to transfer, through conjugation, chloramphenicol (Cm) - marked mutant alleles from engineered Hfr (High frequency of recombination) 'donor strains' into an ordered array of kanamycin (Kan) - marked F- recipient strains. Typically, we use loss-of-function single mutants bearing non-essential gene deletions (e.g. the 'Keio' collection11) and essential gene hypomorphic mutations (i.e. alleles conferring reduced protein expression, stability, or activity9, 12, 13) to query the functional associations of non-essential and essential genes, respectively. After conjugation and ensuing genetic exchange mediated by homologous recombination, the resulting double mutants are selected on solid medium containing both antibiotics. After outgrowth, the plates are digitally imaged and colony sizes are quantitatively scored using an in-house automated image processing system14. GIs are revealed when the growth rate of a double mutant is either significantly better or worse than expected9. Aggravating (or negative) GIs often result between loss-of-function mutations in pairs of genes from compensatory pathways that impinge on the same essential process2. Here, the loss of a single gene is buffered, such that either single mutant is viable. However, the loss of both pathways is deleterious and results in synthetic lethality or sickness (i.e. slow growth). Conversely, alleviating (or positive) interactions can occur between genes in the same pathway or protein complex2 as the deletion of either gene alone is often sufficient to perturb the normal function of the pathway or complex such that additional perturbations do not reduce activity, and hence growth, further. Overall, systematically identifying and analyzing GI networks can provide unbiased, global maps of the functional relationships between large numbers of genes, from which pathway-level information missed by other approaches can be inferred9.

Mapping Bacterial Functional Networks and Pathways in Escherichia Coli using Synthetic Genetic Arrays

Systematic, large-scale synthetic genetic (gene-gene or epistasis) interaction screens can be used to explore genetic redundancy and pathway cross-talk. Here, we describe a high-throughput quantitative synthetic genetic array screening technology, termed eSGA that we developed for elucidating epistatic relationships and exploring genetic interaction networks in Escherichia coli.

Сопоставление бактериальных функциональных сетей и путей в<em&gt; Escherichia Coli</em&gt; Использование синтетических генетических массивы

Phenotypes  are determined by a complex series of physical (e.g. protein-protein) and  functional (e.g. gene-gene or genetic) interactions (GI)1. While ...

Identification of Protein Complexes in Escherichia coli using Sequential Peptide Affinity Purification in Combination with Tandem Mass Spectrometry

Since most cellular processes are mediated by macromolecular assemblies, the systematic identification of protein-protein interactions (PPI) and the identification of the subunit composition of multi-protein complexes can provide insight into gene function and enhance understanding of biological systems1, 2. Physical interactions can be mapped with high confidence vialarge-scale isolation and characterization of endogenous protein complexes under near-physiological conditions based on affinity purification of chromosomally-tagged proteins in combination with mass spectrometry (APMS). This approach has been successfully applied in evolutionarily diverse organisms, including yeast, flies, worms, mammalian cells, and bacteria1-6. In particular, we have generated a carboxy-terminal Sequential Peptide Affinity (SPA) dual tagging system for affinity-purifying native protein complexes from cultured gram-negative Escherichia coli, using genetically-tractable host laboratory strains that are well-suited for genome-wide investigations of the fundamental biology and conserved processes of prokaryotes1, 2, 7. Our SPA-tagging system is analogous to the tandem affinity purification method developed originally for yeast8, 9, and consists of a calmodulin binding peptide (CBP) followed by the cleavage site for the highly specific tobacco etch virus (TEV) protease and three copies of the FLAG epitope (3X FLAG), allowing for two consecutive rounds of affinity enrichment. After cassette amplification, sequence-specific linear PCR products encoding the SPA-tag and a selectable marker are integrated and expressed in frame as carboxy-terminal fusions in a DY330 background that is induced to transiently express a highly efficient heterologous bacteriophage lambda recombination system10. Subsequent dual-step purification using calmodulin and anti-FLAG affinity beads enables the highly selective and efficient recovery of even low abundance protein complexes from large-scale cultures. Tandem mass spectrometry is then used to identify the stably co-purifying proteins with high sensitivity (low nanogram detection limits).
Here, we describe detailed step-by-step procedures we commonly use for systematic protein tagging, purification and mass spectrometry-based analysis of soluble protein complexes from E. coli, which can be scaled up and potentially tailored to other bacterial species, including certain opportunistic pathogens that are amenable to recombineering. The resulting physical interactions can often reveal interesting unexpected components and connections suggesting novel mechanistic links. Integration of the PPI data with alternate molecular association data such as genetic (gene-gene) interactions and genomic-context (GC) predictions can facilitate elucidation of the global molecular organization of multi-protein complexes within biological pathways. The networks generated for E. coli can be used to gain insight into the functional architecture of orthologous gene products in other microbes for which functional annotations are currently lacking.

Identification of Protein Complexes in Escherichia coli using Sequential Peptide Affinity Purification in Combination with Tandem Mass Spectrometry

Affinity purification of tagged proteins in combination with mass spectrometry (APMS) is a powerful method for the systematic mapping of protein interaction networks and for investigating the mechanistic basis of biological processes. Here, we describe an optimized sequential peptide affinity (SPA) APMS procedure developed for the bacterium Escherichia coli that can be used to isolate and characterize stable multi-protein complexes to near homogeneity even starting from low copy numbers per cell.

Определение белковых комплексов в<em&gt; Кишечной палочки</em&gt; С помощью последовательного аффинной очистки пептидов в сочетании с тандемной масс-спектрометрии

Since most cellular processes are mediated by macromolecular assemblies, the systematic identification of protein-protein interactions (PPI) and the ...

Rapid Protocol for Preparation of Electrocompetent Escherichia coli and Vibrio cholerae

Electroporation has become a widely used method for rapidly and efficiently introducing foreign DNA into a wide range of cells. Electrotransformation has become the method of choice for introducing DNA into prokaryotes that are not naturally competent. Electroporation is a rapid, efficient, and streamlined transformation method that, in addition to purified DNA and competent bacteria, requires commercially available gene pulse controller and cuvettes. In contrast to the pulsing step, preparation of electrocompetent cells is time consuming and labor intensive involving repeated rounds of centrifugation and washes in decreasing volumes of sterile, cold water, or non-ionic buffers of large volumes of cultures grown to mid-logarithmic phase of growth. Time and effort can be saved by purchasing electrocompetent cells from commercial sources, but the selection is limited to commonly employed E. coli laboratory strains. We are hereby disseminating a rapid and efficient method for preparing electrocompetent E. coli, which has been in use by bacteriology laboratories for some time, can be adapted to V. cholerae and other prokaryotes. While we cannot ascertain whom to credit for developing the original technique, we are hereby making it available to the scientific community.

Rapid Protocol for Preparation of Electrocompetent Escherichia coli and Vibrio cholerae

Electroporation is a commonly employed method for introducing DNA into bacteria in a process known as transformation. Traditional protocols for the preparation of electrocompetent cells are time consuming and labor intensive. This article describes an alternate, rapid, and efficient method for the preparation of electrocompetent cells presently employed by some laboratories.

Быстрое Протокол по подготовке Электрокомпетентные<em&gt; Кишечная палочка</em&gt; И<em&gt; Холерный вибрион</em

Electroporation has become a widely used method for rapidly and efficiently introducing foreign DNA into a wide range of cells. Electrotransformation has ...

Detection of Live Escherichia coli O157:H7 Cells by PMA-qPCR

A unique open reading frame (ORF) Z3276 was identified as a specific genetic marker for E. coli O157:H7. A qPCR assay was developed for detection of E. coli O157:H7 by targeting ORF Z3276. With this assay, we can detect as low as a few copies of the genome of DNA of E. coli O157:H7. The sensitivity and specificity of the assay were confirmed by intensive validation tests with a large number of E. coli O157:H7 strains (n = 369) and non-O157 strains (n = 112). Furthermore, we have combined propidium monoazide (PMA) procedure with the newly developed qPCR protocol for selective detection of live cells from dead cells. Amplification of DNA from PMA-treated dead cells was almost completely inhibited in contrast to virtually unaffected amplification of DNA from PMA-treated live cells. Additionally, the protocol has been modified and adapted to a 96-well plate format for an easy and consistent handling of a large number of samples. This method is expected to have an impact on accurate microbiological and epidemiological monitoring of food safety and environmental source.

Detection of Live Escherichia coli O157:H7 Cells by PMA-qPCR

A qPCR assay was developed for detection of Escherichia coli O157:H7 targeting a unique genetic marker, Z3276. The qPCR was combined with propidium monoazide (PMA) treatment for live cell detection. This protocol has been modified and adapted to a 96-well plate format for easy and consistent handling of numerous samples

Обнаружение эфир<em&gt; Кишечная палочка</em&gt; O157: H7 Клетки по PMA-кПЦР

A unique open reading frame (ORF) Z3276 was identified as a specific genetic marker for E. coli O157:H7. A qPCR assay was developed for detection of E. ...

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and the inherent instability of many membrane proteins once solubilized in detergents. A protocol is described that combines ligation independent cloning of membrane proteins as GFP fusions with expression in Escherichia coli detected by GFP fluorescence. This enables the construction and expression screening of multiple membrane protein/variants to identify candidates suitable for further investment of time and effort. The GFP reporter is used in a primary screen of expression by visualizing GFP fluorescence following SDS polyacrylamide gel electrophoresis (SDS-PAGE). Membrane proteins that show both a high expression level with minimum degradation as indicated by the absence of free GFP, are selected for a secondary screen. These constructs are scaled and a total membrane fraction prepared and solubilized in four different detergents. Following ultracentrifugation to remove detergent-insoluble material, lysates are analyzed by fluorescence detection size exclusion chromatography (FSEC). Monitoring the size exclusion profile by GFP fluorescence provides information about the mono-dispersity and integrity of the membrane proteins in different detergents. Protein: detergent combinations that elute with a symmetrical peak with little or no free GFP and minimum aggregation are candidates for subsequent purification. Using the above methodology, the heterologous expression in E. coli of SED (shape, elongation, division, and sporulation) proteins from 47 different species of bacteria was analyzed. These proteins typically have ten transmembrane domains and are essential for cell division. The results show that the production of the SEDs orthologues in E. coli was highly variable with respect to the expression levels and integrity of the GFP fusion proteins. The experiment identified a subset for further investigation.

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

A streamlined approach to screening for the expression of recombinant membrane proteins in Escherichia coli based on fusion to green fluorescent protein is presented.

Зеленый флуоресцентный белок на основе Expression Скрининг мембранных белков в<em&gt; Кишечная палочка</em

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and ...

The Multifaceted Benefits of Protein Co-expression in Escherichia coli

We report here that the expression of protein complexes in vivo in Escherichia coli can be more convenient than traditional reconstitution experiments in vitro. In particular, we show that the poor solubility of Escherichia coli DNA polymerase III &#949; subunit (featuring 3&#8217;-5&#8217; exonuclease activity) is highly improved when the same protein is co-expressed with the &#945; and &#952; subunits (featuring DNA polymerase activity and stabilizing &#949;, respectively). We also show that protein co-expression in E. coli can be used to efficiently test the competence of subunits from different bacterial species to associate in a functional protein complex. We indeed show that the &#945; subunit of Deinococcus radiodurans DNA polymerase III can be co-expressed in vivo with the &#949; subunit of E. coli. In addition, we report on the use of protein co-expression to modulate mutation frequency in E. coli. By expressing the wild-type &#949; subunit under the control of the araBAD promoter (arabinose-inducible), and co-expressing the mutagenic D12A variant of the same protein, under the control of the lac promoter (inducible by isopropyl-thio-&#946;-D-galactopyranoside, IPTG), we were able to alter the E. coli mutation frequency using appropriate concentrations of the inducers arabinose and IPTG. Finally, we discuss recent advances and future challenges of protein co-expression in E. coli.

The Multifaceted Benefits of Protein Co-expression in Escherichia coli

Protein co-expression is a powerful alternative to the reconstitution in vitro of protein complexes, and is of help in performing biochemical and genetic tests in vivo. Here we report on the use of protein co-expression in Escherichia coli to obtain protein complexes, and to tune the mutation frequency of cells.

Многогранная Преимущества белка ко-экспрессия в<em&gt; Кишечная палочка</em

We report here that the expression of protein complexes in vivo in Escherichia coli can be more convenient than traditional reconstitution experiments in ...

Method for Labeling Transcripts in Individual Escherichia coli Cells for Single-molecule Fluorescence In Situ Hybridization Experiments

A method is described for labeling individual messenger RNA (mRNA) transcripts in fixed bacteria for use in single-molecule fluorescence in situ hybridization (smFISH) experiments in E. coli. smFISH allows the measurement of cell-to-cell variability in mRNA copy number of genes of interest, as well as the subcellular location of the transcripts. The main steps involved are fixation of the bacterial cell culture, permeabilization of cell membranes, and hybridization of the target transcripts with sets of commercially available short fluorescently-labeled oligonucleotide probes. smFISH can allow the imaging of the transcripts of multiple genes in the same cell, with limitations imposed by the spectral overlap between different fluorescent markers. Following completion of the protocol illustrated below, cells can be readily imaged using a microscope coupled with a camera suitable for low-intensity fluorescence. These images, together with cell contours obtained from segmentation of phase contrast frames, or from cell membrane staining, allow the calculation of the mRNA copy number distribution of a sample of cells using open-source or custom-written software. The labeling method described here can also be applied to image transcripts with stochastic optical reconstruction microscopy (STORM).

Method for Labeling Transcripts in Individual Escherichia coli Cells for Single-molecule Fluorescence In Situ Hybridization Experiments

This manuscript describes a method for labeling individual messenger RNA (mRNA) transcripts with fluorescently-labeled DNA probes, for use in single-molecule fluorescence in situ hybridization (smFISH) experiments in E. coli. smFISH is a visualization method that allows the simultaneous detection, localization, and quantification of single mRNA molecules in fixed individual cells.

Метод для маркировки стенограммы в клетках отдельных кишечная палочка для одной молекулы флуоресценции в Situ гибридизация экспериментов

Исследование подвижности жгутиков у кишечной палочки путем применения трех установленных методов в серии

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