Funding sources: University of Connecticut Research Foundation and the Department of Molecular and Cell Biology to SVN, Sigma Xi Grant-in-Aid-of Research and Antonio H. and Majorie R. 
Romano Graduate Education Fellowship to AJC

<ol>
 <li>Prepare 500 mLs of 0.22 &mu;m filter-sterilized artificial seawater (FSW; salinity 35 ppt). Filter artificial or natural seawater through a 0.22 &mu;m micron filter to remove particles and bacteria.</li>
 <li>Anesthetize one adult Hawaiian bobtail squid (Euprymna scolopes) by placing in a 2% solution of ethanol in FSW. Place the animal in anesthetic for approximately 10 minutes. The squid will cease swimming and will not actively respond to touch. Continued respiration, indicated by movement of the mantle, and chromatophore activity should still be observed.</li>
 <li>Place squid with ventral side facing up on a standard wax dissection tray. Submerge the animal with FSW containing 2% ethanol.</li>
 <li>Using one standard 200 &mu;l pipette tips, pull back the funnel and mantle to expose the main cephalic blood vessel located between the two eyes.</li>
 <li>Using a sterile 1 mL syringe with 26.5-gauge needle, puncture the cephalic blood vessel and withdraw between 50-100 &mu;l of hemolymph. Place the hemolymph in a sterile 1.5 mL tube on ice. Note: If an animal will serve as a donor multiple times, only withdraw 10-20 &mu;l of hemolymph at any given time. Return the animal to a normal seawater tank. The animal will revive within 30 min.</li>
 <li>Freshly collected hemocytes are washed and re-suspended in 500 &mu;l of Squid Ringer s solution (S-Ringers; 530 mM NaCl, 10 mM KCl, 25 mM MgCl2, 10 mM CaCl2 and 10 mM HEPES buffer, pH 7.5). </li>
 <li>Hemocyte concentrations are determined by hemocytometer, and approximately 2,000 cells are added to chambered glass cover slips, and allowed to adhere to the glass for 10 min at room temperature. At this density, the hemocytes form a uniform monolayer on the glass slide surface.</li>
 <li>To observe bacterial binding to host hemocytes, hemocytes are exposed to a fluorescently labeled bacterial strain such as Vibrio fischeri ES114 and/or Vibrio harveyi B392, each containing a green fluorescent reporter. V. fischeri ES114 and V. harveyi B392 are grown to mid-log phase in a sea water tryptone media (SWT) at 28&deg;C in an orbital shaker. The optical density at 600nm is measured spectrophotometrically to determine cell density. The bacteria are pelleted by centrifugation (5,000 rpm for 5 min), the supernatant is discarded, and the pellet is re-suspended in S-Ringers.</li>
 <li> 100,000 bacterial cells are added to each chamber well so that there are 50 bacteria per hemocyte on average. The hemocyte/bacteria mixtures are incubated in S-Ringer s solution at 25&deg;C for 1 h, a time determined to yield the maximum level of binding. </li>
 <li>The cytoplasm of the hemocytes are then fluorescently stained with 0.005% CellTracker Orange (Invitrogen) and then washed in S-Ringers to visualize the cells. </li>
 <li>Stained hemocytes with associated bacteria are viewed by fluorescence using either a Zeiss Discovery V20 fluorescent stereoscope or a Leica SP2 spectral laser confocal microscope, and enumerated over the entire surface of the animal cell.</li>
</ol>
Representative Results
Because cephalopod hemolymph contains extracellular hemocyanin and not hemoglobin, upon oxygenation, the hemolymph will turn dark blue. An average of ~5000 hemocytes per &mu;l of hemolymph will be obtained using this method. After adherence to the chambered cover slips and fluorescent staining, the hemocytes should appear brightly fluorescently red and amoeboid in shape. For bacterial adhesion, V. fischeri will adhere poorly to the hemocytes (1-2 bacterial cells per blood cell) while V. harveyi will adhere strongly (10-15 bacterial cells per hemocyte).
<img src="/files/ftp_upload/1714/1714fig1.jpg" alt="Figure 1" /> Figure 1. Adult Hawaiian bobtail squid Euprymna scolopes showing position of cephalic blood vessel.
<img src="/files/ftp_upload/1714/1714fig2.jpg" alt="Figure 2" /> Figure 2. Results of hemocyte exposure to Vibrio fischeri (A) and Vibrio harveyi (B). Red, Cell Tracker Orange; Green, GFP-labeled bacteria.

<ol>
	<li>Koropatnick, T. A., Kimbell, J. R., McFall-Ngai, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Responses+of+host+hemocytes+during+the+initiation+of+the+squid-Vibrio+symbiosis.">Responses of host hemocytes during the initiation of the squid-Vibrio symbiosis.</a> Biol. Bull. 212, 29-39 (2007).</li><li>McFall-Ngai, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unseen+forces:+the+influence+of+bacteria+on+animal+development.">Unseen forces: the influence of bacteria on animal development.</a> Dev. Biol. 242, 1-14 (2002).</li><li>McFall-Ngai, M. J., Ruby, E. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Symbiont+recognition+and+subsequent+morphogenesis+as+early+events+in+an+animal-bacterial+mutualism.">Symbiont recognition and subsequent morphogenesis as early events in an animal-bacterial mutualism.</a> Science. 254, 1491-1494 (1991).</li><li>Nyholm, S. V., Stewart, J. J., Ruby, E. G., McFall-Ngai, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recognition+between+symbiotic+Vibrio+fischeri+and+the+haemocytes+of+Euprymna+scolopes.">Recognition between symbiotic Vibrio fischeri and the haemocytes of Euprymna scolopes.</a> Environ. Microbiol. 11, 483-493 (2009).</li><li>Nyholm, S. V., McFall-Ngai, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+winnowing:+establishing+the+squid-Vibrio+symbiosis.">The winnowing: establishing the squid-Vibrio symbiosis.</a> Nat. Rev. Microbiol. 2, 632-642 (2004).</li><li>Nyholm, S. V., Stabb, E. V., Ruby, E. G., McFall-Ngai, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishment+of+an+animal-bacterial+association:+recruiting+symbiotic+Vibrios+from+the+environment.">Establishment of an animal-bacterial association: recruiting symbiotic Vibrios from the environment.</a> Proc. Natl. Acad. Sci. USA. 97, 10231-10235 (2000).</li><li>Nyholm, S. V., McFall-Ngai, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sampling+the+light-organ+microenvironment+of+Euprymna+scolopes:+description+of+a+population+of+host+cells+in+association+with+the+bacterial+symbiont+Vibrio+fischeri.">Sampling the light-organ microenvironment of Euprymna scolopes: description of a population of host cells in association with the bacterial symbiont Vibrio fischeri.</a> Biol Bull. 195, 89-97 (1998).</li><li>Visick, K. L., Ruby, E. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vibrio+fischeri+and+its+host:+it+takes+two+to+tango.">Vibrio fischeri and its host: it takes two to tango.</a> Curr. Opin. Microbiol. 9, 632-638 (2006).</li></ol>

Studies concerning the role of the immune system in mediating molecular signaling between beneficial bacteria and their hosts have, in recent years, made significant contributions to our understanding of the co-evolution of eukaryotes with their microbiota. The squid/vibrio system has proven itself as a tractable model system to answer fundamental questions in this field2,3,5,6,8. The light-organ of the squid Euprymna scolopes permits colonization exclusively by the luminous bacterium Vibrio fisc...

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		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
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<tr>
<td>Lab-Tek chambered #1.0 borosilicate coverglass system (8-chambers)</td>
<td>&nbsp;</td>
<td>Thermo-Fisher Scientific</td>
<td>155411</td>
<td>&nbsp;</td>
<tr>
<td>26.5 G 1ml latex-free insulin syringe</td>
<td>&nbsp;</td>
<td>Becton, Dickinson and Company</td>
<td>C34551</td>
<td>&nbsp;</td>
<tr>
<td>Cell Tracker Orange</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>C34551</td>
<td>&nbsp;</td>
<tr>
<td>SteREO Discovery V20 Microscope</td>
<td>&nbsp;</td>
<td>Zeiss</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>SP2 Confocal Microscope</td>
<td>&nbsp;</td>
<td>Leica</td>
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obtaining hemocytes from the hawaiian bobtail squid euprymna scolopes and observing their adherence to symbiotic and non-symbiotic bacteria

Studies concerning the role of the immune system in mediating molecular signaling between beneficial bacteria and their hosts have, in recent years, made significant contributions to our understanding of the co-evolution of eukaryotes with their microbiota. The symbiotic association between the Hawaiian bobtail squid, Euprymna scolopes and the bioluminescent bacterium Vibrio fischeri has been utilized as a model system for understanding the effects of beneficial bacteria on animal development. Recent studies have shown that macrophage-like hemocytes, the sole cellular component of the squid host's innate immune system, likely play an important role in mediating the establishment and maintenance of this association. This protocol will demonstrate how to obtain hemocytes from E. scolopes and then use these cells in bacterial binding assays. Adult squid are first anesthetized before hemolymph is collected by syringe from the main cephalic blood vessel. The host hemocytes, contained in the extracted hemolymph, are adhered to chambered glass coverslips and then exposed to green fluorescent protein-labeled symbiotic Vibrio fischeri and non-symbiotic Vibrio harveyi. The hemocytes are counterstained with a fluorescent dye (Cell Tracker Orange, Invitrogen) and then visualized using fluorescent microscopy.

Watch this Scientific Journal Video about Obtaining Hemocytes from the Hawaiian Bobtail Squid Euprymna scolopes and Observing their Adherence to Symbiotic and Non-Symbiotic Bacteria at JoVE.com

Obtaining Hemocytes from the Hawaiian Bobtail Squid Euprymna scolopes and Observing their Adherence to Symbiotic and Non-Symbiotic Bacteria

This video will demonstrate how to obtain hemocytes (blood cells) from the Hawaiian bobtail squid, Euprymna scolopes for use in cell biological and bacterial adhesion assays. Hemocytes will be stained with a fluorescent dye and exposed to GFP-labeled bacteria.

Obtaining Hemocytes from the Hawaiian Bobtail Squid Euprymna scolopes and Observing their Adherence to Symbiotic and Non-Symbiotic Bacteria

Studies concerning the role of the immune system in mediating molecular signaling between beneficial bacteria and their hosts have, in recent years, made ...

obtaining-hemocytes-from-hawaiian-bobtail-squid-euprymna-scolopes

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JoVE Journal

Biology

13.1K Views.  University of Connecticut. This video will demonstrate how to obtain hemocytes (blood cells) from the Hawaiian bobtail squid, Euprymna scolopes for use in cell biological and bacterial adhesion assays. Hemocytes will be stained with a fluorescent dye and exposed to GFP-labeled bacteria.

Video: Obtaining Hemocytes from the Hawaiian Bobtail Squid Euprymna scolopes and Observing their Adherence to Symbiotic and Non-Symbiotic Bacteria

Obtaining Eggs from Xenopus laevis Females

The eggs of Xenopus laevis intact, lysed, and/or fractionated are useful for a wide variety of experiments. This protocol shows how to induce egg laying, collect and dejelly the eggs, and sort the eggs to remove any damaged eggs.

The eggs of Xenopus laevis intact, lysed, and/or fractionated are useful for a wide variety of experiments. This protocol shows how to induce egg laying, collect and dejelly the eggs, and sort the eggs to remove any damaged eggs.

The eggs of Xenopus laevis intact, lysed, and/or fractionated are useful for a wide variety of experiments. This protocol shows how to induce egg laying, ...

Formulations for Freeze-drying of Bacteria and Their Influence on Cell Survival

Cellular water can be removed to reversibly inactivate microorganisms to facilitate storage. One such method of removal is freeze-drying, which is considered a gentle dehydration method. To facilitate cell survival during drying, the cells are often formulated beforehand. The formulation forms a matrix that embeds the cells and protects them from various harmful stresses imposed on the cells during freezing and drying. We present here a general method to evaluate the survival rate of cells after freeze-drying and we illustrate it by comparing the results obtained with four different formulations: the disaccharide sucrose, the sucrose derived polymer Ficoll PM400, and the respective polysaccharides hydroxyethyl cellulose (HEC) and hydroxypropyl methyl cellulose (HPMC), on two strains of bacteria, P. putida KT2440 and A. chlorophenolicus A6. In this work we illustrate how to prepare formulations for freeze-drying and how to investigate the mechanisms of cell survival after rehydration by characterizing the formulation using of differential scanning calorimetry (DSC), surface tension measurements, X-ray analysis, and electron microscopy and relating those data to survival rates. The polymers were chosen to get a monomeric structure of the respective polysaccharide resembling sucrose to a varying degrees. Using this method setup we showed that polymers can support cell survival as effectively as disaccharides if certain physical properties of the formulation are controlled1.

Freeze-drying is often an easy and convenient way to obtain dry products of viable bacterial cells. An issue of the process is cell survival. We detail here a procedure to investigate how cell survival during freeze-drying is influenced by the properties of the formulation used.

Cellular water can be removed to reversibly inactivate microorganisms to facilitate storage. One such method of removal is freeze-drying, which is ...

A Simple Protocol for Extracting Hemocytes from Wild Caterpillars

Insect hemocytes (equivalent to mammalian white blood cells) play an important role in several physiological processes throughout an insect's life cycle 1. In larval stages of insects belonging to the orders of Lepidoptera (moths and butterflies) and Diptera (true flies), hemocytes are formed from the lymph gland (a specialized hematopoietic organ) or embryonic cells and can be carried through to the adult stage. Embryonic hemocytes are involved in cell migration during development and chemotaxis regulation during inflammation. They also take part in cell apoptosis and are essential for embryogenesis 2. Hemocytes mediate the cellular arm of the insect innate immune response that includes several functions, such as cell spreading, cell aggregation, formation of nodules, phagocytosis and encapsulation of foreign invaders 3. They are also responsible for orchestrating specific insect humoral defenses during infection, such as the production of antimicrobial peptides and other effector molecules 4, 5. Hemocyte morphology and function have mainly been studied in genetic or physiological insect models, including the fruit fly, Drosophila melanogaster 6, 7, the mosquitoes Aedes aegypti and Anopheles gambiae 8, 9 and the tobacco hornworm, Manduca sexta 10, 11. However, little information currently exists about the diversity, classification, morphology and function of hemocytes in non-model insect species, especially those collected from the wild 12.
Here we describe a simple and efficient protocol for extracting hemocytes from wild caterpillars. We use penultimate instar Lithacodes fasciola (yellow-shouldered slug moth) (Figure 1) and Euclea delphinii (spiny oak slug) caterpillars (Lepidoptera: Limacodidae) and show that sufficient volumes of hemolymph (insect blood) can be isolated and hemocyte numbers counted from individual larvae. This method can be used to efficiently study hemocyte types in these species as well as in other related lepidopteran caterpillars harvested from the field, or it can be readily combined with immunological assays designed to investigate hemocyte function following infection with microbial or parasitic organisms 13.

Insect hemocytes carry out many important functions, both immune and non-immune, throughout all stages of insect development. Our present knowledge of hemocyte types and function comes from studies on insect genetic models. Here, we present a method for extracting, quantifying and visualizing hemocytes from wild caterpillars.

Insect hemocytes (equivalent to mammalian white blood cells) play an important role in several physiological processes throughout an insect's life cycle ...

Isolation and Culture of Individual Myofibers and their Satellite Cells from Adult Skeletal Muscle

Muscle regeneration in the adult is performed by resident stem cells called satellite cells. Satellite cells are defined by their position between the basal lamina and the sarcolemma of each myofiber. Current knowledge of their behavior heavily relies on the use of the single myofiber isolation protocol. In 1985, Bischoff described a protocol to isolate single live fibers from the Flexor Digitorum Brevis (FDB) of adult rats with the goal to create an in vitro system in which the physical association between the myofiber and its stem cells is preserved 1. In 1995, Rosenblattmodified the Bischoff protocol such that myofibers are singly picked and handled separately after collagenase digestion instead of being isolated by gravity sedimentation 2, 3. The Rosenblatt or Bischoff protocol has since been adapted to different muscles, age or conditions 3-6. The single myofiber isolation technique is an indispensable tool due its unique advantages. First, in the single myofiber protocol, satellite cells are maintained beneath the basal lamina. This is a unique feature of the protocol as other techniques such as Fluorescence Activated Cell Sorting require chemical and mechanical tissue dissociation 7. Although the myofiber culture system cannot substitute for in vivo studies, it does offer an excellent platform to address relevant biological properties of muscle stem cells. Single myofibers can be cultured in standard plating conditions or in floating conditions. Satellite cells on floating myofibers are subjected to virtually no other influence than the myofiber environment. Substrate stiffness and coating have been shown to influence satellite cells' ability to regenerate muscles 8, 9 so being able to control each of these factors independently allows discrimination between niche-dependent and -independent responses. Different concentrations of serum have also been shown to have an effect on the transition from quiescence to activation. To preserve the quiescence state of its associated satellite cells, fibers should be kept in low serum medium 1-3. This is particularly useful when studying genes involved in the quiescence state. In serum rich medium, satellite cells quickly activate, proliferate, migrate and differentiate, thus mimicking the in vivo regenerative process 1-3. The system can be used to perform a variety of assays such as the testing of chemical inhibitors; ectopic expression of genes by virus delivery; oligonucleotide based gene knock-down or live imaging. This video article describes the protocol currently used in our laboratory to isolate single myofibers from the Extensor Digitorum Longus (EDL) muscle of adult mice (6-8 weeks old).

Isolation and culture of myofibers is the gold standard in vitro system to study the transition of satellite cells through quiescence, activation and differentiation. Importantly, the single myofiber culture system preserves the myofiber/stem cell association, which is an essential component of the muscle stem cell niche.

Muscle  regeneration in the adult is performed by resident stem cells called satellite  cells. Satellite cells are defined by  their position between the ...

Collection, Isolation and Enrichment of Naturally Occurring Magnetotactic Bacteria from the Environment

Magnetotactic bacteria (MTB) are aquatic microorganisms that were first notably described in 19751 from sediment samples collected in salt marshes of Massachusetts (USA). Since then MTB have been discovered in stratified water- and sediment-columns from all over the world2. One feature common to all MTB is that they contain magnetosomes, which are intracellular, membrane-bound magnetic nanocrystals of magnetite (Fe3O4) and/or greigite (Fe3S4) or both3, 4. In the Northern hemisphere, MTB are typically attracted to the south end of a bar magnet, while in the Southern hemisphere they are usually attracted to the north end of a magnet3,5. This property can be exploited when trying to isolate MTB from environmental samples.
One of the most common ways to enrich MTB is to use a clear plastic container to collect sediment and water from a natural source, such as a freshwater pond. In the Northern hemisphere, the south end of a bar magnet is placed against the outside of the container just above the sediment at the sediment-water interface. After some time, the bacteria can be removed from the inside of the container near the magnet with a pipette and then enriched further by using a capillary racetrack6 and a magnet. Once enriched, the bacteria can be placed on a microscope slide using a hanging drop method and observed in a light microscope or deposited onto a copper grid and observed using transmission electron microscopy (TEM).
Using this method, isolated MTB may be studied microscopically to determine characteristics such as swimming behavior, type and number of flagella, cell morphology of the cells, shape of the magnetic crystals, number of magnetosomes, number of magnetosome chains in each cell, composition of the nanomineral crystals, and presence of intracellular vacuoles.

We demonstrate a method to collect magnetotactic bacteria (MTB) that can be applied to natural waters. MTB can be isolated and enriched from sediment samples using a relatively simple setup that takes advantage of the bacteria's natural magnetism. Isolated MTB can then be examined in detail using both light and electron microscopy.

Magnetotactic bacteria (MTB) are aquatic microorganisms that were first notably described in 19751 from sediment samples collected in salt marshes of ...

A Method for Extracting Pigments from Squid Doryteuthis pealeii

Cephalopods can undergo rapid and adaptive changes in dermal coloration for sensing, communication, defense, and reproduction purposes. These capabilities are supported in part by the areal expansion and retraction of pigmented organs known as chromatophores. While it is known that the chromatophores contain a tethered network of pigmented granules, their structure-function properties have not been fully detailed. We describe a method for isolating the nanostructured granules in squid Doryteuthis pealeii chromatophores and demonstrate how their associated pigments can be extracted in acidic solvents. To accomplish this, the chromatophore containing dermal layer is first manually isolated using a superficial dissection, and the pigment granules are removed using sonication, centrifugation, and washing cycles. Pigments confined within the purified granules are then extracted via acidic methanol solutions, leaving nanostructures with smaller diameters that are void of visible color. This extraction procedure produces a 58% yield of soluble pigments isolated from granules. Using this method, the composition of the chromatophore pigments can be determined and used to provide insight into the mechanism of adaptive coloration in cephalopods.

A Method for Extracting Pigments from Squid Doryteuthis pealeii

A protocol for the extraction of pigments from the nanostructured granules in squid Doryteuthis pealeii chromatophores is presented.

Cephalopods can undergo rapid and adaptive changes in dermal coloration for sensing, communication, defense, and reproduction purposes. These capabilities ...

Split Green Fluorescent Protein System to Visualize Effectors Delivered from Bacteria During Infection

Bacteria, one of the most important causative agents of various plant diseases, secrete a set of effector proteins into the host plant cell to subvert the plant immune system. During infection cytoplasmic effectors are delivered to the host cytosol via a type III secretion system (T3SS). After delivery into the plant cell, the effector(s) targets the specific compartment(s) to modulate host cell processes for survival and replication of the pathogen. Although there has been some research on the subcellular localization of effector proteins in the host cells to understand their function in pathogenicity by using fluorescent proteins, investigation of the dynamics of effectors directly injected from bacteria has been challenging due to the incompatibility between the T3SS and fluorescent proteins.
Here, we describe our recent method of an optimized split superfolder green fluorescent protein system (sfGFPOPT) to visualize the localization of effectors delivered via the bacterial T3SS in the host cell. The sfGFP11 (11th &#946;-strand of sfGFP)-tagged effector secreted through the T3SS can be assembled with a specific organelle targeted sfGFP1-10OPT (1-10th &#946;-strand of sfGFP) leading to fluorescence emission at the site. This protocol provides a procedure to visualize the reconstituted sfGFP fluorescence signal with an effector protein from Pseudomonas syringae in a particular organelle in the Arabidopsis and Nicotiana benthamiana plants.

Fluorescent protein-based approaches to monitor effectors secreted by bacteria into host cells are challenging. This is due to the incompatibility between fluorescent proteins and the type-III secretion system. Here, an optimized split superfolder GFP system is used for visualization of effectors secreted by bacteria into the host plant cell.

Bacteria, one of the most important causative agents of various plant diseases, secrete a set of effector proteins into the host plant cell to subvert the ...

Isolation of High Quality Murine Atrial and Ventricular Myocytes for Simultaneous Measurements of Ca2+ Transients and L-Type Calcium Current

Mouse models play a crucial role in arrhythmia research and allow studying key mechanisms of arrhythmogenesis including altered ion channel function and calcium handling. For this purpose, atrial or ventricular cardiomyocytes of high quality are necessary to perform patch-clamp measurements or to explore calcium handling abnormalities. However, the limited yield of high-quality cardiomyocytes obtained by current isolation protocols does not allow both measurements in the same mouse. This article describes a method to isolate high-quality murine atrial and ventricular myocytes via retrograde enzyme-based Langendorff perfusion, for subsequent simultaneous measurements of calcium transients and L-type calcium current from one animal. Mouse hearts are obtained, and the aorta is rapidly cannulated to remove blood. Hearts are then initially perfused with a calcium-free solution (37 &#176;C) to dissociate the tissue at the level of intercalated discs and afterwards with an enzyme solution containing little calcium to disrupt extracellular matrix (37 &#176;C). The digested heart is subsequently dissected into atria and ventricles. Tissue samples are chopped into small pieces and dissolved by carefully pipetting up and down. The enzymatic digestion is stopped, and cells are stepwise reintroduced to physiologic calcium concentrations. After loading with a fluorescent Ca2+-indicator, isolated cardiomyocytes are prepared for simultaneous measurement of calcium currents and transients. Additionally, isolation pitfalls are discussed and patch-clamp protocols and representative traces of L-type calcium currents with simultaneous calcium transient measurements in atrial and ventricular murine myocytes isolated as described above are provided.

Isolation of High Quality Murine Atrial and Ventricular Myocytes for Simultaneous Measurements of Ca2+ Transients and L-Type Calcium Current

Mouse models allow studying key mechanisms of arrhythmogenesis. For this purpose, high quality cardiomyocytes are necessary to perform patch-clamp measurements. Here, a method to isolate murine atrial and ventricular myocytes via retrograde enzyme-based Langendorff perfusion, which allows simultaneous measurements of calcium-transients and L-type calcium current, is described.

Mouse models play a crucial role in arrhythmia research and allow studying key mechanisms of arrhythmogenesis including altered ion channel function and ...

Establishing Stable Binary Cultures of Symbiotic Saccharibacteria from the Oral Cavity

Many bacterial species cannot be cultured in the laboratory using standard methods, posing a significant barrier to studying the majority of microbial diversity on earth. Novel approaches are required to culture these uncultured bacteria so that investigators can effectively study their physiology and lifestyle using the powerful tools available in the laboratory. The Candidate Phyla Radiation (CPR) is one of the largest groups of uncultivated bacteria, comprising ~15% of the living diversity on earth. The first isolate of this group was a member of the Saccharibacteria phylum, 'Nanosynbacter lyticus' strain TM7x. TM7x is an unusually small bacterium that lives as a symbiont in direct contact with a bacterial host, Schaalia odontolytica, strain XH001. Taking advantage of the unusually small cell size and its lifestyle as a symbiotic organism, we developed a protocol to rapidly culture Saccharibacteria from dental plaque. This protocol will show how to filter a suspension of dental plaque through a 0.2 &#181;m filter, then concentrate the collected Saccharibacteria cells and infect a culture of host organisms. The resulting coculture can be passaged as any normal bacterial culture and infection is confirmed by PCR. The resulting binary culture can be maintained in the laboratory and used for future experiments. While contamination is a possibility, the binary culture can be purified by either further filtering and reinfection of host, or by plating the binary culture and screening for infected colonies. We hope this protocol can be expanded to other sample types and environments, leading to the cultivation of many more species in the CPR.

We demonstrate a method for isolating difficult-to-grow members of the novel bacterial phylum, Saccharibacteria, by filtering dental plaque and co-culturing with host bacteria.

Many bacterial species cannot be cultured in the laboratory using standard methods, posing a significant barrier to studying the majority of microbial ...

Scalable Isolation and Purification of Extracellular Vesicles from Escherichia coli and Other Bacteria

Diverse bacterial species secrete ~20-300 nm extracellular vesicles (EVs), comprised of lipids, proteins, nucleic acids, glycans, and other molecules derived from the parental cells. EVs function as intra- and inter-species communication vectors while also contributing to the interaction between bacteria and host organisms in the context of infection and colonization. Given the multitude of functions attributed to EVs in health and disease, there is a growing interest in isolating EVs for in vitro and in vivo studies. It was hypothesized that the separation of EVs based on physical properties, namely size, would facilitate the isolation of vesicles from diverse bacterial cultures. 
The isolation workflow consists of centrifugation, filtration, ultrafiltration, and size-exclusion chromatography (SEC) for the isolation of EVs from bacterial cultures. A pump-driven tangential flow filtration (TFF) step was incorporated to enhance scalability, enabling the isolation of material from liters of starting cell culture. Escherichia coli was used as a model system expressing EV-associated nanoluciferase and non-EV-associated mCherry as reporter proteins. The nanoluciferase was targeted to the EVs by fusing its N-terminus with cytolysin A. Early chromatography fractions containing 20-100 nm EVs with associated cytolysin A - nanoLuc were distinct from the later fractions containing the free proteins. The presence of EV-associated nanoluciferase was confirmed by immunogold labeling and transmission electron microscopy. This EV isolation workflow is applicable to other human gut-associated gram-negative and gram-positive bacterial species. In conclusion, combining centrifugation, filtration, ultrafiltration/TFF, and SEC enables scalable isolation of EVs from diverse bacterial species. Employing a standardized isolation workflow will facilitate comparative studies of microbial EVs across species.

Scalable Isolation and Purification of Extracellular Vesicles from Escherichia coli and Other Bacteria

Bacteria secrete nanometer-sized extracellular vesicles (EVs) carrying bioactive biological molecules. EV research focuses on understanding their biogenesis, role in microbe-microbe and host-microbe interactions and disease, as well as their potential therapeutic applications. A workflow for scalable isolation of EVs from various bacteria is presented to facilitate standardization of EV research.

Diverse bacterial species secrete ~20-300 nm extracellular vesicles (EVs), comprised of lipids, proteins, nucleic acids, glycans, and other molecules ...