This work was supported by grants from the U.S. National Science Foundation (EAR-0920299 and EAR-0745808); U.S. National Science Foundation East Asian and Pacific Summer Institutes; the Geological Society of America Research Grant Program and the Alumni Grants for Graduate Research and Scholarship from The Ohio State University. We would like to thank the editor and two anonymous reviewers for their insightful comments.

1. MTB Collection
<ol>
	<li>When deciding on a freshwater site to collect magnetotactic bacteria (MTB), it is often best to start with a pond or slow-moving stream that has a soft muddy sediment layer. In this demonstration we collected a sample at the edge of the Olentangy River on the campus of The Ohio State University (OSU) in Columbus, Ohio (USA). While this was a convenient location for our demonstration, the protocol described here is applicable to any aquatic location. The materials used in this protocol can be found in Table 1. Find a location where the depth of the water is between 10 and 100 cm. At such a location, you should collect the upper-most layer of sediment using a clear, screw-top container. Scoop the sediment and water into the container until it is filled with one-third to one-half sediment and the remaining volume with water. Keep the container submerged until it is filled with water and then tightly cap the container with its screw-top lid. It's not necessary to mix the sediment. Wipe the outside of the container dry with a towel and then take the sample to your laboratory. It's not necessary to rush the sample back to your laboratory. We've left MTB samples in plastic containers in the field for several days before bringing them back to our laboratory. The MTB should be viable for several weeks to months as long as you store the samples in a cool, shaded place in the field.</li>
	<li>Once the sample is in your laboratory, loosen the cap and leave it covering the container to reduce the amount of evaporation. Store the container at room temperature in a dark room, drawer, or completely cover the container with aluminum foil. Allow the sediment and fine particles to completely settle to the bottom of the container by leaving the sample undisturbed for several hours to several days. It is not necessary to mix the sediment, MTB prefer an undisturbed environment. The clear walls of the plastic container will allow you to confirm that the particles have settled to the bottom. Depending on your sample, MTB can remain alive in the sample for many months.</li>
</ol>
2. MTB Isolation
<ol>
	<li>When you are ready to isolate the MTB, place magnets on the sides of the plastic container approximately 1 cm above the sediment-water interface (Figure 1A). Be careful not to disturb the sediment in the bottom of the container. Place the south pole of a bar magnet on one side of the container and the north side of another bar magnet on the opposite side (Figure 1A). Almost any magnet can be used, such as a magnetic stir bar or large refrigerator magnet. Anything can be used to support the magnets at the correct height above the sediment-water interface. We've found that resting the magnets on the top of a cardboard or plastic box is best, however, the magnets can also be taped to the outside of the plastic container. Wait 30 min to several hours for the bacteria to swim to the magnet.</li>
	<li>Use a sterile pipette to carefully collect the water from inside the container (Figure 1A) near the position of the south-pole bar magnet (for samples collected in the Northern hemisphere). This water should contain the MTB that have been attracted to the south-pole bar magnet. Next, a capillary racetrack should be used to further enrich the MTB.</li>
</ol>
3. MTB Racetrack
<ol>
	<li>In order to enrich your sample with magnetotactic bacteria, a capillary racetrack is necessary (Figures 1B and 1C). These need to be made prior to isolating the cells from the clear-plastic container.</li>
	<li>Use a 5.75 inch (146 mm) glass Pasteur pipette to make a racetrack. Use a diamond pen or file to cut off the top of the pipette, the length of the pipette is not crucial, but it should be able to contain approximately 1-2 ml of water. Next, use a Bunsen burner to melt the tip so that it becomes sealed (Figure 1C). The resulting pipette should have an open end and a sealed end.</li>
	<li>Make several of these racetracks and then autoclave. Additionally, you will need to autoclave cotton and several long metal needles.</li>
	<li>Add filtered sample water, collected from near the sediment water interface shown in Figure 1A, to an autoclaved racetrack using a long metal needle attached to a filtered syringe. The pore size of the filter should be 0.22 mm to eliminate debris and contaminants from the water. It is important to be absolutely sure that there are no air bubbles in the glass capillary.</li>
	<li>Plug the bottom of the racetrack with sterile cotton (Figure 1B). Use the metal needle to push the cotton towards the sealed end of the racetrack so it is 0.5 - 1 cm away from the sealed tip (Figure 1C).</li>
	<li>Using a sterile pipette, add the MTB-containing water (from section 2.2) to the sample reservoir (open end) of a prepared MTB racetrack (Figure 1B).</li>
</ol>
4. MTB Enrichment
<ol>
	<li>Once the racetrack is filled with sample fluid, lay it on its side on a horizontal surface (e.g., a benchtop) and place the south pole of a bar magnet (in the Northern hemisphere) next to the sealed tip of the racetrack (Figures 1B and 1C).</li>
	<li>Wait 5 to 30 min for the MTB to migrate through the cotton. Then you should collect the fluid near the tip of the racetrack. Waiting too long can introduce contaminants, such as other motile bacteria, to the tip of the capillary. Optionally, you could use a light microscope to view the tip of the racetrack and watch the MTB collect at the racetrack's tip. This will allow you to determine how long it takes the MTB to migrate through the cotton plug.</li>
	<li>Gently use the diamond knife to make a little scratch near cotton plug and snap off the end of the racetrack.</li>
	<li>Use a 1 ml syringe with a narrow needle (25 or 27 gauge) to remove the fluid from the tip of the racetrack. This liquid sample should now contain the enriched MTB.</li>
</ol>
5. MTB Observation by Light Microscopy
<ol>
	<li>Place a drop (10-20 &mu;l) of the enriched MTB sample onto a coverslip.</li>
	<li>Quickly flip the coverslip over so the drop is now facing down and hanging from the coverslip.</li>
	<li>Place the coverslip onto an o-ring that is resting on a glass slide. The o-ring should have a slightly smaller diameter then the coverslip (about 1 cm; Figure 2).</li>
	<li>Place this hanging drop onto a light microscope stage and focus on one edge of the drop. A 60X dry objective works very well because most have a high numerical aperture (NA; e.g., 0.93) but do not require oil, which is difficult to use for the hanging drop method (Figure 2).</li>
	<li>Place the south end of a bar magnet close to the hanging drop and MTB will begin to migrate towards the edge of the drop closest to the magnet (Figure 3). Within a few minutes many MTB should be at the edge of the drop (Figure 3). Prove to yourself that the bacteria are magnetic by reversing the pole of the magnet and then observe the bacteria swim in the opposite direction.</li>
</ol>
6. MTB Observation by Transmission Electron Microscopy (TEM)
<ol>
	<li>Place a drop (~20 &mu;l) of the enriched MTB onto a copper grid and allow the bacteria to settle for 10 min.</li>
	<li>Wick off excess water with a piece of clean filter paper.</li>
	<li>Optionally, the grid can be negatively stained with 2% uranyl acetate, 2% phosphotungstic acid pH 7.2, or 2.5% sodium molybdate7, 8, 9. This is done by placing the copper grid onto a drop of stain immediately after incubating the grid with the enriched MTB. Incubate the grid with the negative stain, the times will vary depending on the stain used, and then wick off the fluid with a piece of clean filter paper.</li>
	<li>Observe the MTB using transmission electron microscopy (TEM, Figure 4). For the work described here MTB were adsorbed to Formvar stabilized and carbon coated 200 mesh copper grids (Ted Pella #01800). The grids were placed with the carbon side down on a drop of cell suspension for up to 10 min, then immediately washed one time by placing the grid on a drop of water for 30 sec. For staining, the grids were placed on a drop of 2% uranyl acetate (Ted Pella #19481) for 30 sec to 5 min and then dried completely using a piece of filter paper. The grids were analyzed by TEM using either an FEI Tecnai Spirit at 80kV or a FEI Tecnai F20 using high angle annular dark field STEM at 200kV.</li>
</ol>

<ol>
	<li>Blakemore, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetotactic+bacteria.">Magnetotactic bacteria.</a> Science. 190, 377-379 (1975).</li><li>Blakemore, R. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetotactic+bacteria.">Magnetotactic bacteria.</a> Annual Reviews in Microbiology. 36, 217-238 (1982).</li><li>Bazylinski, D. A., Frankel, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+Biomineralization+of+Magnetite+(Fe3O4)+and+Greigite+(Fe3S4)+in+a+Magnetotactic+Bacterium.">Controlled Biomineralization of Magnetite (Fe3O4) and Greigite (Fe3S4) in a Magnetotactic Bacterium.</a> Applied and Environmental Microbiology. 61, 3232-3239 (1995).</li><li>Lefevre, C. T., Menguy, N., 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=A+Cultured+Greigite-Producing+Magnetotactic+Bacterium+in+a+Novel+Group+of+Sulfate-Reducing+Bacteria.">A Cultured Greigite-Producing Magnetotactic Bacterium in a Novel Group of Sulfate-Reducing Bacteria.</a> Science. 334, 1720-1723 (2011).</li><li>Simmons, S. L., Bazylinski, D. 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=South-seeking+magnetotactic+bacteria+in+the+Northern+Hemisphere.">South-seeking magnetotactic bacteria in the Northern Hemisphere.</a> Science. 311, 371-374 (2006).</li><li>Wolfe, R., Thauer, R., 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=A+'capillary+racetrack'+method+for+isolation+of+magnetotactic+bacteria.">A 'capillary racetrack' method for isolation of magnetotactic bacteria.</a> FEMS Microbiology Letters. 45, 31-35 (1987).</li><li>Rodgers, F. G., Blakemore, R. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intercellular+structure+in+a+many-celled+magnetotactic+prokaryote.">Intercellular structure in a many-celled magnetotactic prokaryote.</a> Archives of Microbiology. 154, 18-22 (1990).</li><li>Moench, T. T., Konetzka, W., 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=A+novel+method+for+the+isolation+and+study+of+a+magnetotactic+bacterium.">A novel method for the isolation and study of a magnetotactic bacterium.</a> Archives of Microbiology. 119, 203-212 (1978).</li><li>Balkwill, D., Maratea, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrastructure+of+a+magnetotactic+spirillum.">Ultrastructure of a magnetotactic spirillum.</a> Journal of Bacteriology. 141, 1399-1408 (1980).</li><li>Lins, U., Freitas, F., 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=Simple+homemade+apparatus+for+harvesting+uncultured+magnetotactic+microorganisms.">Simple homemade apparatus for harvesting uncultured magnetotactic microorganisms.</a> Brazilian Journal of Microbiology. 34, 111-116 (2003).</li><li>Jogler, C., Lin, W., 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=Toward+Cloning+of+the+Magnetotactic+Metagenome:+Identification+of+Magnetosome+Island+Gene+Clusters+in+Uncultivated+Magnetotactic+Bacteria+from+Different+Aquatic+Sediments.">Toward Cloning of the Magnetotactic Metagenome: Identification of Magnetosome Island Gene Clusters in Uncultivated Magnetotactic Bacteria from Different Aquatic Sediments.</a> Applied and Environmental Microbiology. 75, 3972-3979 (2009).</li><li>Lin, W., Li, 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=Newly+Isolated+but+Uncultivated+Magnetotactic+Bacterium+of+the+Phylum+Nitrospirae+from+Beijing,+China.">Newly Isolated but Uncultivated Magnetotactic Bacterium of the Phylum Nitrospirae from Beijing, China.</a> Applied and Environmental Microbiology. 78, 668-675 (2012).</li><li>Li, J., Pan, 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=Biomineralization,+crystallography+and+magnetic+properties+of+bullet-shaped+magnetite+magnetosomes+in+giant+rod+magnetotactic+bacteria.">Biomineralization, crystallography and magnetic properties of bullet-shaped magnetite magnetosomes in giant rod magnetotactic bacteria.</a> Earth and Planetary Science Letters. 293, 368-376 (2010).</li><li>Oestreicher, Z., Valerde-Tercedor, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetosomes+and+magnetite+crystals+produced+by+magnetotactic+bacteria+as+resolved+by+atomic+force+microscopy+and+transmission+electron+microscopy.">Magnetosomes and magnetite crystals produced by magnetotactic bacteria as resolved by atomic force microscopy and transmission electron microscopy.</a> Micron. 43, 1331-1335 (2012).</li></ol>

No conflicts of interest declared.

Magnetotactic bacteria are not necessarily found in every aquatic environment8 but when they do occur, they can be found on the order of 100 - 1,000 cells per milliliter2. In order to observe the MTB using optical microscopy, you will need approximately 50 bacteria/ml in your sample8. If there are no or few MTB in your sample, then you will either need to select a new environmental site to collect your samples or you will need to try one or more of the techniques discussed in the next sec...

<table border="1">
 <tbody>
 <tr>
 <td>Item Name</td>
 <td>Company</td>
 <td>Catalogue number</td>
 <td>Comments (optional)</td>
 </tr>
 <tr>
 <td>Glass slides</td>
 <td>Fisher Scientific</td>
 <td>S95933 </td>
 <td></td>
 </tr>
 <tr>
 <td>Glass Pasteur pipets</td>
 <td>Fisher Scientific</td>
 <td>13-678-6A</td>
 <td></td>
 </tr>
 <tr>
 <td>O-ring</td>
 <td>Hardware store</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Cover slips</td>
 <td>Fisher Scientific</td>
 <td>12-542B</td>
 <td></td>
 </tr>
 <tr>
 <td>Bar magnet</td>
 <td>Fisher Scientific</td>
 <td>S95957</td>
 <td></td>
 </tr>
 <tr>
 <td>Container</td>
 <td>Any</td>
 <td></td>
 <td>Any plastic or glass container that can hold at least 0.5 L and can be sealed</td>
 </tr>
 <tr>
 <td>Cotton</td>
 <td>Any</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Microscope with 60X dry lens</td>
 <td>Zeiss</td>
 <td></td>
 <td>A 60X dry lens is not absolutely necessary, but this gives a high NA without using oil</td>
 </tr>
 <tr>
 <td>Diamond pen</td>
 <td>Fisher Scientific</td>
 <td>08-675</td>
 <td></td>
 </tr>
 <tr>
 <td>0.22 mm filter</td>
 <td>Fisher Scientific</td>
 <td>09-719C</td>
 <td></td>
 </tr>
 <tr>
 <td>1 ml syringe</td>
 <td>Fisher Scientific</td>
 <td>NC9788564</td>
 <td></td>
 </tr>
 <tr>
 <td>Microcentrifuge tubes</td>
 <td>Fisher Scientific</td>
 <td>02-681-320</td>
 <td></td>
 </tr>
 <tr>
 <td>Formvar/Carbon 200 mesh, copper grids</td>
 <td>Ted Pella Inc.</td>
 <td>01800</td>
 <td></td>
 </tr>
 <tr>
 <td>Uranyl acetate</td>
 <td>Ted Pella Inc.</td>
 <td>19481</td>
 <td></td>
 </tr>
 <tr>
 <td>Tecnai Spirit TEM</td>
 <td>FEI</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Tecnai F20 S/TEM</td>
 <td>FEI</td>
 <td></td>
 <td></td>
 </tr>
 </tbody>
 </table>

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.

A magnet is an effective tool that can be used to isolate magnetotactic bacteria (MTB) contained in environmental samples (Figure 1A). A capillary racetrack (Figure 1B) uses the magnetic properties of MTB to attract them through a cotton plug where they can be separated from non-magnetotactic microorganisms also contained within the environmental sample.
<img alt="Figure 1" src="/files/ftp_upload/50123/50123fig1.jpg" /><b...

Watch this Scientific Journal Video about Collection, Isolation and Enrichment of Naturally Occurring Magnetotactic Bacteria from the Environment at JoVE.com

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

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 ...

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22.9K Views.  The Ohio State University. 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.

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

Enrichment of NK Cells from Human Blood with the RosetteSep Kit from StemCell Technologies

Natural killer (NK) cells are large granular cytotoxic lymphocytes that belong to the innate immune system and play major roles in fighting against cancer and infections, but are also implicated in the early stages of pregnancy and transplant rejection. These cells are present in peripheral blood, from which they can be isolated. Cells can be isolated using either positive or negative selection. For positive selection we use antibodies directed to a surface marker present only on the cells of interest whereas for negative selection we use cocktails of antibodies targeted to surface markers present on all cells but the cells of interest. This latter technique presents the advantage of leaving the cells of interest free of antibodies, thereby reducing the risk of unwanted cell activation or differenciation. In this video-protocol we demonstrate how to separate NK cells from human blood by negative selection, using the RosetteSep kit from StemCell technologies. The procedure involves obtaining human peripheral blood (under an institutional review board-approved protocol to protect the human subjects) and mixing it with a cocktail of antibodies that will bind to markers absent on NK cells, but present on all other mononuclear cells present in peripheral blood (e.g., T lymphocytes, monocytes...). The antibodies present in the cocktail are conjugated to antibodies directed to glycophorin A on erythrocytes. All unwanted cells and red blood cells will therefore be trapped in complexes. The mix of blood and antibody cocktail is then diluted, overlayed on a Histopaque gradient, and centrifuged. NK cells (&gt;80% pure) can be collected at the interface between the Histopaque and the diluted plasma. Similar cocktails are available for enrichment of other cell populations, such as human T lymphocytes.

Natural killer cells are a small population of lymphocytes. Here we show how to isolate these cells from human blood by negative selection, using a kit from StemCell Technologies. The cells obtained are viable and untouched by antibodies, and therefore ready to be used for a number of procedures.

Natural killer (NK) cells are large granular cytotoxic lymphocytes that belong to the innate immune system and play major roles in fighting against cancer ...

Blood Collection from the American Horseshoe Crab, Limulus Polyphemus

The horseshoe crab has the best-characterized immune system of any long-lived invertebrate. The study of immunity in horseshoe crabs has been facilitated by the ease in collecting large volumes of blood and from the simplicity of the blood. Horseshoe crabs show only a single cell type in the general circulation, the granular amebocyte. The plasma has the salt content of sea water and only three abundant proteins, hemocyanin, the respiratory protein, the C-reactive proteins, which function in the cytolytic destruction of foreign cells, including bacterial cells, and &alpha;2-macroglobulin, which inhibits the proteases of invading pathogens. Blood is collected by direct cardiac puncture under conditions that minimize contamination by lipopolysaccharide (a.k.a., endotoxin, LPS), a product of the Gram-negative bacteria. A large animal can yield 200 - 400 mL of blood. For the study of the plasma, blood cells are immediately removed from the plasma by centrifugation and the plasma can then be fractionated into its constituent proteins. The blood cells are conveniently studied microscopically by collecting small volumes of blood into LPS-free isotonic saline (0.5 M NaCl) under conditions that permit direct microscopic examination by placing one of more LPS-free coverglasses on the culture dish surface, then mounting those coverglasses in simple observation chambers following cell attachment. A second preparation for direct observation is to collect 3 - 5 mL of blood in a LPS-free embryo dish and then explanting fragments of aggregated amebocytes to a chamber that sandwiches the tissue between a slide and a coverglass. In this preparation, the motile amebocytes migrate onto the coverglass surface, where they can readily be observed. The blood clotting system involves aggregation of amebocytes and the formation of an extracellular clot of a protein, coagulin, which is released from the secretory granules of the blood cells. Biochemical analysis of washed blood cells requires that aggregation and degranulation does not occur, which can be accomplished by collecting blood into 0.1 volumes of 2% Tween-20, 0.5 M LPS-free NaCl, followed by centrifugation of the cells and washing with 0.5 M NaCl.

The American horseshoe crab, Limulus polyphemus, is arguably the most convenient source for large quantities of blood of any invertebrate. The blood is simple in composition, with only one cell-type in the general circulation, the granular amebocyte, and only three abundant proteins in the plasma, hemocyanin, the C-reactive proteins, and &alpha;2-macroglobulin. Blood is collected from the heart and the blood cells and plasma are separated by centrifugation.

The horseshoe crab has the best-characterized immune system of any long-lived invertebrate.  The study of immunity in horseshoe crabs has been facilitated ...

Isolation of Small Noncoding RNAs from Human Serum

The analysis of RNA and its expression is a common feature in many laboratories. Of significance is the emergence of small RNAs like microRNAs, which are found in mammalian cells. These small RNAs are potent gene regulators controlling vital pathways such as growth, development and death and much interest has been directed at their expression in bodily fluids. This is due to their dysregulation in human diseases such as cancer and their potential application as serum biomarkers. However, the analysis of miRNA expression in serum may be problematic. In most cases the amount of serum is limiting and serum contains low amounts of total RNA, of which small RNAs only constitute 0.4-0.5%1. Thus the isolation of sufficient amounts of quality RNA from serum is a major challenge to researchers today. In this technical paper, we demonstrate a method which uses only 400 &#181;l of human serum to obtain sufficient RNA for either DNA arrays or qPCR analysis. The advantages of this method are its simplicity and ability to yield high quality RNA. It requires no specialized columns for purification of small RNAs and utilizes general reagents and hardware found in common laboratories. Our method utilizes a Phase Lock Gel to eliminate phenol contamination while at the same time yielding high quality RNA. We also introduce an additional step to further remove all contaminants during the isolation step. This protocol is very effective in isolating yields of total RNA of up to 100 ng/&#181;l from serum but can also be adapted for other biological tissues.

This protocol describes a method for extracting small RNAs from human serum. We have used this method to isolate microRNAs from cancer serum for use in DNA arrays and also singleplex quantitative PCR. The protocol utilizes phenol and guanidinium thiocyanate reagents with modifications to yield high quality RNA.

The analysis of RNA and its expression is a common feature in many laboratories. Of significance is the emergence of small RNAs like microRNAs, which are ...

Avian Semen Collection by Cloacal Massage and Isolation of DNA from Sperm

Collection of semen may be useful for a wide range of applications including studies involving sperm quality, sperm telomere dynamics, and epigenetics. Birds are widely used subjects in biological research and are ideal for studies involving repeated sperm samples. However, few resources are currently available for those wishing to learn how to collect and extract DNA from avian sperm. Here we describe cloacal massage, a gentle, non-invasive manual technique for collecting avian sperm. Although this technique is established in the literature, it can be difficult to learn from the available descriptions. We also provide information for extracting DNA from avian semen using a commercial extraction kit with modifications. Cloacal massage can be easily used on any small- to medium-sized male bird in reproductive condition. Following collection, the semen can be used immediately for motility assays, or frozen for DNA extraction following the protocol described herein. This extraction protocol was refined for avian sperm and has been successfully used on samples collected from several passerine species (Passer domesticus, Spizella passerina, Haemorhous mexicanus, and Turdus migratorius) and one columbid (Columba livia).

This protocol describes cloacal massage, a non-invasive manual technique for collecting semen from birds, and DNA extraction from avian sperm using a commercial extraction kit with modifications.

Collection of semen may be useful for a wide range of applications including studies involving sperm quality, sperm telomere dynamics, and epigenetics. ...

Growing Magnetotactic Bacteria of the Genus Magnetospirillum: Strains MSR-1, AMB-1 and MS-1

Magnetotactic bacteria are Gram-negative, motile, mainly aquatic prokaryotes ubiquitous in freshwater and marine habitats. They are characterized by their ability to biomineralize magnetosomes, which are magnetic nanometer-sized crystals of magnetite (Fe3O4) or greigite (Fe3S4) surrounded by a lipid bilayer membrane, within their cytoplasm. For most known magnetotactic bacteria, magnetosomes are assembled in chains inside the cytoplasm, thereby conferring a permanent magnetic dipole moment to the cells and causing them to align passively with external magnetic fields. Because of these specific features, magnetotactic bacteria have a great potential for commercial and medical applications. However, most species are microaerophilic and have specific O2 concentration requirements, making them more difficult to grow routinely than many other bacteria such as Escherichia coli. Here we present detailed protocols for growing three of the most widely studied strains of magnetotactic bacteria, all belonging to the genus Magnetospirillum. These methods allow for precise control of the O2 concentration made available to the bacteria, in order to ensure that they grow normally and synthesize magnetosomes. Growing magnetotactic bacteria for further studies using these procedures does not require the experimentalist to be an expert in microbiology. The general methods presented in this article may also be used to isolate and culture other magnetotactic bacteria, although it is likely that growth media chemical composition will need to be modified.

Growing Magnetotactic Bacteria of the Genus Magnetospirillum: Strains MSR-1, AMB-1 and MS-1

We present a procedure for growing several strains of Magnetospirillum in two different types of growth media. Magnetospirillum gryphiswaldense strain MSR-1 is grown in both liquid and O2 concentration gradient semi-solid media while M. magneticum strain AMB-1 and M. magnetotacticum strain MS-1 are grown in liquid medium.

Magnetotactic bacteria are Gram-negative, motile, mainly aquatic prokaryotes ubiquitous in freshwater and marine habitats. They are characterized by their ...

Isolation of Myoepithelial Cells from Adult Murine Lacrimal and Submandibular Glands

The lacrimal gland (LG) is an exocrine tubuloacinar gland that secretes an aqueous layer of tear film. The LG epithelial tree is comprised of acinar, ductal epithelial, and myoepithelial cells (MECs). MECs express alpha smooth muscle actin (&#945;SMA) and have a contractile function. They are found in multiple glandular organs and are of ectodermal origin. In addition, the LG contains SMA+ vascular smooth muscle cells of endodermal origin called pericytes: contractile cells that envelop the surface of vascular tubes. A new protocol allows us to isolate both MECs and pericytes from adult murine LGs and submandibular glands (SMGs). The protocol is based on the genetic labeling of MECs and pericytes using the SMACreErt2/+:Rosa26-TdTomatofl/fl mouse strain, followed by preparation of the LG single-cell suspension for fluorescence activated cell sorting (FACS). The protocol allows for the separation of these two cell populations of different origins based on the expression of the epithelial cell adhesion molecule (EpCAM) by MECs, whereas pericytes do not express EpCAM. Isolated cells could be used for cell cultivation or gene expression analysis.

The lacrimal gland (LG) has two cell types expressing &#945;-smooth muscle actin (&#945;SMA): myoepithelial cells (MECs) and pericytes. MECs are of ectodermal origin, found in many glandular tissues, while pericytes are vascular smooth muscle cells of endodermal origin. This protocol isolates MECs and pericytes from murine LGs.

The lacrimal gland (LG) is an exocrine tubuloacinar gland that secretes an aqueous layer of tear film. The LG epithelial tree is comprised of acinar, ...

Isolation and Enrichment of Human Lung Epithelial Progenitor Cells for Organoid Culture

Epithelial organoid models serve as valuable tools to study the basic biology of an organ system and for disease modeling. When grown as organoids, epithelial progenitor cells can self-renew and generate differentiating progeny that exhibit cellular functions similar to those of their in vivo counterparts. Herein we describe a step-by-step protocol to isolate region-specific progenitors from human lung and generate 3D organoid cultures as an experimental and validation tool. We define proximal and distal regions of the lung with the goal of isolating region-specific progenitor cells. We utilized a combination of enzymatic and mechanical dissociation to isolate total cells from the lung and trachea. Specific progenitor cells were then fractionated from the proximal or distal origin cells using fluorescence associated cell sorting (FACS) based on cell type-specific surface markers, such as NGFR&#160;for sorting basal cells and HTII-280 for sorting alveolar type II cells. Isolated basal or alveolar type II progenitors were used to generate 3D organoid cultures. Both distal and proximal progenitors formed organoids with a colony forming efficiency of 9-13% in distal region and 7-10% in proximal region when plated 5000 cell/well on day 30. Distal organoids maintained HTII-280+ alveolar type II cells in culture whereas proximal organoids differentiated into ciliated and secretory cells by day 30. These 3D organoid cultures can be used as an experimental tool for studying the cell biology of lung epithelium and epithelial mesenchymal interactions, as well as for the development and validation of therapeutic strategies targeting epithelial dysfunction in a disease.

This article provides a detailed methodology for tissue dissociation and cellular fractionation approaches allowing enrichment of viable epithelial cells from proximal and distal regions of the human lung. Herein these approaches are applied for the functional analysis of lung epithelial progenitor cells through the use of 3D organoids culture models.

Epithelial organoid models serve as valuable tools to study the basic biology of an organ system and for disease modeling. When grown as organoids, ...

Collection and Identification of Pollen from Honey Bee Colonies

Researchers often collect and analyze corbicular pollen from honey bees to identify the plant sources on which they forage for pollen or to estimate pesticide exposure of bees via pollen. Described herein is an effective pollen-trapping method for collecting corbicular pollen from honey bees returning to their hives. This collection method results in large quantities of corbicular pollen that can be used for research purposes. Honey bees collect pollen from many plant species, but typically visit one species during each collection trip. Therefore, each corbicular pollen pellet predominantly represents one plant species, and each pollen pellet can be described by color. This allows the sorting of samples of corbicular pollen by color to segregate plant sources. Researchers can further classify corbicular pollen by analyzing the morphology of acetolyzed pollen grains for taxonomic identification. These methods are commonly used in studies related to pollinators such as pollination efficiency, pollinator foraging dynamics, diet quality, and diversity. Detailed methodologies are presented for collecting corbicular pollen using pollen traps, sorting pollen by color, and acetolyzing pollen grains. Also presented are results pertaining to the frequency of pellet colors and taxa of corbicular pollen collected from honey bees in five different cropping systems.

We describe methods for collecting corbicular pollen from honey bees as well as protocols for color sorting, acetolysis, and microscope slide preparation of pollen for taxonomic identification. In addition, we present pellet color and taxonomic diversity of corbicular pollen collected from five cropping systems using pollen traps.

Researchers often collect and analyze corbicular pollen from honey bees to identify the plant sources on which they forage for pollen or to estimate ...

Swabbing the Urban Environment - A Pipeline for Sampling and Detection of SARS-CoV-2 From Environmental Reservoirs

To control community transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during the 2020 global pandemic, most countries implemented strategies based on direct human testing, face covering, and surface disinfection. Under the assumption that the main route of transmission includes aerosols and respiratory droplets, efforts to detect SARS-CoV-2 in fomites have focused on locations suspected of high prevalence (e.g., hospital wards, cruise ships, and mass transportation systems). To investigate the presence of SARS-CoV-2 on surfaces in the urban environment that are rarely cleaned and&#160;seldomly disinfected, 350 citizens were enlisted from the greater San Diego County. In total, these citizen scientists collected 4,080 samples. An online platform was developed to monitor sampling kit delivery and pickup, as well as to collect sample data. The sampling kits were mostly built from supplies available in pandemic-stressed stores. Samples were processed using reagents that were easy to access despite the recurrent supply shortage. The methods used were highly sensitive and resistant to inhibitors that are commonly present in environmental samples. The proposed experimental design and processing methods were successful at engaging numerous citizen scientists who effectively gathered samples from diverse surface areas. The workflow and methods described here are relevant to survey the urban environment for other viruses, which are of public health concern and pose a threat for&#160;future pandemics.

A citizen science project was designed to recruit San Diego residents to collect environmental samples for SARS-CoV-2. A multilingual web-based platform was created for data submission using a user-friendly mobile device interface. A laboratory information management system facilitated the collection of thousands of geographically diverse samples with real-time outcome tracking.

To control community transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during the 2020 global pandemic, most countries ...

Rapid In Vivo Fixation and Isolation of Translational Complexes from Eukaryotic Cells

Rapid responses involving fast redistribution of messenger(m)RNA and alterations of mRNA translation are pertinent to ongoing homeostatic adjustments of the cells. These adjustments are critical to eukaryotic cell survivability and &#39;damage control&#39; during fluctuating nutrient and salinity levels, temperature, and various chemical and radiation stresses. Due to the highly dynamic nature of the RNA-level responses, and the instability of many of the RNA:RNA and RNA:protein intermediates, obtaining a meaningful snapshot of the cytoplasmic RNA state is only possible with a limited number of methods. Transcriptome-wide, RNA-seq-based ribosome profiling-type experiments are among the most informative sources of data for the control of translation. However, absence of a uniform RNA and RNA:protein intermediate stabilization can lead to different biases, particularly in the fast-paced cellular response pathways. In this article, we provide a detailed protocol of rapid fixation applicable to eukaryotic cells of different permeability, to aid in RNA and RNA:protein intermediate stabilization. We further provide examples of isolation of the stabilized RNA:protein complexes based on their co-sedimentation with ribosomal and poly(ribo)somal fractions. The separated stabilized material can be subsequently used as part of ribosome profiling-type experiments, such as in Translation Complex Profile sequencing (TCP-seq) approach and its derivatives. Versatility of the TCP-seq-style methods has now been demonstrated by the applications in a variety of organisms and cell types. The stabilized complexes can also be additionally affinity-purified and imaged using electron microscopy, separated into different poly(ribo)somal fractions and subjected to RNA sequencing, owing to the ease of the crosslink reversal. Therefore, methods based on snap-chilling and formaldehyde fixation, followed by the sedimentation-based or other type of RNA:protein complex enrichment, can be of particular interest in investigating finer details of rapid RNA:protein complex dynamics in live cells.

Rapid In Vivo Fixation and Isolation of Translational Complexes from Eukaryotic Cells

We present a technique to rapidly stabilize translational (protein biosynthesis) complexes with formaldehyde crosslinking in live yeast and mammalian cells. The approach enables dissecting transient intermediates and dynamic RNA:protein interactions. The crosslinked complexes can be used in multiple downstream applications such as in deep sequencing-based profiling methods, microscopy, and mass-spectrometry.

Rapid responses involving fast redistribution of messenger(m)RNA and alterations of mRNA translation are pertinent to ongoing homeostatic adjustments of ...