Name: isolation and characterization of extracellular vesicles produced by iron-limited mycobacteria
Uploaded: 2019-10-31T14:30:00
Description: Watch this Scientific Journal Video about Isolation and Characterization of Extracellular Vesicles Produced by Iron-limited Mycobacteria at JoVE.com

We are grateful to Rafael Prados-Rosales for sharing the anti-MEV antisera and Navneet Dogra for performing nanoparticle tracking analysis.

1. Preparation of Iron-depleted Defined Medium
<ol>
	<li>Prepare 1 L of minimal medium (MM) by dissolving 5 g of KH2PO4, 5 g of L-asparagine, 20 mL of glycerol, and 2 g of dextrose in 900 mL of deionized water in a plastic container. Avoid glass to prevent iron contamination. Adjust the pH to 6.8 with 5 N NaOH and the volume to 1 L with water.</li>
	<li>Add 50 g of metal chelating resin (MCR) and gently agitate using a magnetic stir bar for 24 h at 4 &#176;C. Sterilize and remove the MCR by filtra...

<ol>
	<li>Prados-Rosales, 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=Mycobacteria+release+active+membrane+vesicles+that+modulate+immune+responses+in+a+TLR2-dependent+manner+in+mice.">Mycobacteria release active membrane vesicles that modulate immune responses in a TLR2-dependent manner in mice.</a> Journal of Clinical Investigation. 121, 1471-1483 (2011).</li><li>Gupta, S., Rodriguez, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mycobacterial+extracellular+vesicles+and+host+pathogen+interactions.">Mycobacterial extracellular vesicles and host pathogen interactions.</a> Pathogens and Disease. 76 (4), (2018).</li><li>Athman, J. 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=Bacterial+Membrane+Vesicles+Mediate+the+Release+of+Mycobacterium+tuberculosis+Lipoglycans+and+Lipoproteins+from+Infected+Macrophages.">Bacterial Membrane Vesicles Mediate the Release of Mycobacterium tuberculosis Lipoglycans and Lipoproteins from Infected Macrophages.</a> Journal of Immunology. 195, 1044-1053 (2015).</li><li>Athman, J. 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=Mycobacterium+tuberculosis+Membrane+Vesicles+Inhibit+T+Cell+Activation.">Mycobacterium tuberculosis Membrane Vesicles Inhibit T Cell Activation.</a> Journal of Immunology. 198, 2028-2037 (2017).</li><li>Rath, P., 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=Genetic+regulation+of+vesiculogenesis+and+immunomodulation+in+Mycobacterium+tuberculosis.">Genetic regulation of vesiculogenesis and immunomodulation in Mycobacterium tuberculosis.</a> Proceedings of the National Academy of Science U.S.A. 110, E4790-E4797 (2013).</li><li>White, D. W., Elliott, S. R., Odean, E., Bemis, L. T., Tischler, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mycobacterium+tuberculosis+Pst/SenX3-RegX3+Regulates+Membrane+Vesicle+Production+Independently+of+ESX-5+Activity.">Mycobacterium tuberculosis Pst/SenX3-RegX3 Regulates Membrane Vesicle Production Independently of ESX-5 Activity.</a> mBio. 9, pii 00778 (2018).</li><li>Dauros Singorenko, P., 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=Isolation+of+membrane+vesicles+from+prokaryotes:+a+technical+and+biological+comparison+reveals+heterogeneity.">Isolation of membrane vesicles from prokaryotes: a technical and biological comparison reveals heterogeneity.</a> Journal of Extracellular Vesicles. 6, 1324731 (2017).</li><li>Prados-Rosales, R., Brown, L., Casadevall, A., Montalvo-Quiros, S., Luque-Garcia, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+identification+of+membrane+vesicle-associated+proteins+in+Gram-positive+bacteria+and+mycobacteria.">Isolation and identification of membrane vesicle-associated proteins in Gram-positive bacteria and mycobacteria.</a> MethodsX. 1, 124-129 (2014).</li><li>Prados-Rosales, 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=Role+for+Mycobacterium+tuberculosis+membrane+vesicles+in+iron+acquistion.">Role for Mycobacterium tuberculosis membrane vesicles in iron acquistion.</a> Journal of Bacteriology. 196, 1250-1256 (2014).</li><li>Sanders, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aseptic+Laboratory+Techniques:+Plating+Methods.">Aseptic Laboratory Techniques: Plating Methods.</a> Journal of Visualized Experiments. 63, e3064 (2012).</li><li>Harlow, E., Lane, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Antibodies. A laboratory manual. , (1988).</li><li>Lotvall, 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=Minimal+experimental+requirements+for+definition+of+extracellular+vesicles+and+their+functions:+a+position+statement+from+the+International+Society+for+Extracellular+Vesicles.">Minimal experimental requirements for definition of extracellular vesicles and their functions: a position statement from the International Society for Extracellular Vesicles.</a> Journal of Extracellular Vesicles. 3, 26913 (2014).</li></ol>

Multiple methods to purify eukaryotic cell-derived exosomes have been developed12. In contrast, there is limited information on effective methods to purify bacteria-derived EVs7. Efficient isolation of Mtb-derived EVs needs to consider the intrinsic difficulties in growing this pathogenic mycobacterium. Mtb has a long division time (~24 h) and should be handled in biosafety level three (BSL-3) conditions. Therefore, it is important to optimize the efficiency of MEV isolatio...

Mycobacterial extracellular vesicles (MEVs) are membrane-bound nanoparticles, 60&#8722;300 nm in size, naturally released by fast- and slow-growing mycobacteria1. MEVs released by pathogenic mycobacteria constitute a mechanism to interact with the host via immunologically active proteins, lipids, and glycolipids secreted in a concentrated and protected manner2,3,4. To characterize MEVs and understand their biogenesis and functions, strict and efficient methods of vesicle purification and validation are crucial. Thus far, MEVs have been isolated from the culture filtrates of mycobacteria grown in an iron-rich medium1,5,6,7,8.
However, previous work demonstrated that iron limitation greatly stimulates vesicle release in Mtb,possibly to capture iron via mycobactin, a siderophore secreted in MEVs9. Although procedures for MEVs isolation from Mtb cultured in high iron medium have been described, an efficient methodology to obtain MEVs from low iron cultures has not been reported. Therefore, the goal of this method is to isolate, purify, and quantify MEVs obtained from low iron cultures so that they can be used for biochemical and functional assays and for the analysis of genetic determinants of vesicle production in mycobacteria.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Amicon stirred cell Model 108</td>
			<td>EMD Milipore</td>
			<td>UFSC40001</td>
			<td>Cell Ultrafiltration system</td>
		</tr>
		<tr>
			<td>BD Polypropilene 225 ml conical tubes</td>
			<td>Fisher</td>
			<td>05-538-61</td>
			<td>Conical centrifuge tubes</td>
		</tr>
		<tr>
			<td>Biomax 100-kDa cut-off ultrafiltration membrane</td>
			<td>EMD Milipore</td>
			<td>PBHK07610</td>
			<td>Ultrafiltration membrane</td>
		</tr>
		<tr>
			<td>Chelex-100 resin</td>
			<td>Bio-Rad</td>
			<td>142-2842</td>
			<td>Metal chelating resin</td>
		</tr>
		<tr>
			<td>Middlebrook 7H10 Agar</td>
			<td>BD Difco</td>
			<td>262710</td>
			<td>Mycobacterial Agar plates</td>
		</tr>
		<tr>
			<td>Middlebrook 7H9 Broth</td>
			<td>BD Difco</td>
			<td>271310</td>
			<td>Mycobacterial broth medium</td>
		</tr>
		<tr>
			<td>Nitro cellulose blotting membrane</td>
			<td>GE Healthcare</td>
			<td>10600001</td>
			<td>Blotting Membrane</td>
		</tr>
		<tr>
			<td>Optiprep</td>
			<td>Sigma</td>
			<td>D1556</td>
			<td>Iodixanol</td>
		</tr>
		<tr>
			<td>Polycarbonate ultra centrifugation tubes 25 x 89 mm</td>
			<td>Beckman Coulter</td>
			<td>355618</td>
			<td>Polycarbonate ultra centrifugation tubes 25 x 89 mm</td>
		</tr>
		<tr>
			<td>Polypropylene thin walled centrifuge tube 13x15 mm</td>
			<td>Beckman Coulter</td>
			<td>344059</td>
			<td>Polypropylene thin walled centrifuge tube 13x15 mm</td>
		</tr>
		<tr>
			<td>Protein Assay dye</td>
			<td>BioRad</td>
			<td>5000006</td>
			<td>Bradford Protein Staining</td>
		</tr>
		<tr>
			<td>SYPRO Ruby</td>
			<td>Molecular Probes</td>
			<td>S12000</td>
			<td>Ultrasensitive protein stain</td>
		</tr>
		<tr>
			<td>TMA-DPH</td>
			<td>Molecular Probes</td>
			<td>T204</td>
			<td>1-(4-Trimethylammoniumphenyl)-6-Phenyl-1,3,5-Hexatriene p-Toluenesulfonate</td>
		</tr>
		<tr>
			<td>Vacuum filtration flasks</td>
			<td>CellPro</td>
			<td>V50022</td>
			<td>Filter Unit</td>
		</tr>
	</tbody>
</table>

isolation and characterization of extracellular vesicles produced by iron-limited mycobacteria

Mycobacteria, including Mycobacterium tuberculosis (Mtb), the causative agent of human tuberculosis, naturally release extracellular vesicles (EVs) containing immunologically active molecules. Knowledge regarding the molecular mechanisms of vesicle biogenesis, the content of the vesicles, and their functions at the pathogen-host interface is very limited. Addressing these questions requires rigorous procedures for isolation, purification, and validation of EVs. Previously, vesicle production was found to be enhanced when M. tuberculosis was exposed to iron restriction, a condition encountered by Mtb in the host environment. Presented here is a complete and detailed protocol to isolate and purify EVs from iron-deficient mycobacteria. Quantitative and qualitative methods are applied to validate purified EVs.

MEVs were purified by differential sedimentation in a density gradient (Figure 1, Figure 2). Under the conditions described, MEVs separated mostly in gradient fraction 3 (F3), which corresponds to 25% iodixanol. This conclusion is based on the detection of protein, membrane lipid, microscopic visualization of intact MEVs, nanoparticle size distribution, and positive reactivity with an antivesicle antiserum (F...

Watch this Scientific Journal Video about Isolation and Characterization of Extracellular Vesicles Produced by Iron-limited Mycobacteria at JoVE.com

Isolation and Characterization of Extracellular Vesicles Produced by Iron-limited Mycobacteria

Mycobacterium tuberculosis shows increased production and release of extracellular vesicles in response to low iron conditions. This work details a protocol for generating low iron conditions and methods for the purification and characterization of mycobacterial extracellular vesicles released in response to iron deficiency.

Mycobacteria, including Mycobacterium tuberculosis (Mtb), the causative agent of human tuberculosis, naturally release extracellular vesicles (EVs) ...

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