This research was funded by the Spanish Ministry of Science, Innovation and Universities (RTI2018-098777-B-I00), the FEDER Funds, and the Generalitat of Catalunya (2017SGR-229). Sandra Guallar-Garrido is the recipient of a PhD contract (FI) from the Generalitat de Catalunya.

1. Extraction of the total non-covalent-linked lipids from mycobacteria (Figure 1)
<ol>
	<li>Scratch 0.2 g of mycobacteria from a solid media and add to a glass tube with a polytetrafluoroethlene (PTFE) liner screw caps. Add a solution consisting of 5 mL of chloroform and 10 mL of methanol (chloroform:methanol, 1:2). 
	NOTE: When organic solvents are used, only glass recipient should be used. No plastic containers are allowed. Moreover, PTFE liner screw caps for bottles are needed. 
	CAUTION: Chloroform is a potentially toxic and extremely hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves). 
	CAUTION: Methanol is a potentially toxic and extremely hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves).</li>
	<li>Leave the tube in constant stirring overnight to extract non-covalent-linked lipids from the mycobacterial cell surface. 
	NOTE: If an orbital shaking platform is not available, constant stirring can be replaced by periodic manual stirring as frequently as possible.</li>
	<li>Cover a glass funnel with a filter paper, filter the organic solvents, and collect them in a glass tube.</li>
	<li>Use a nitrogen gas flux to evaporate the liquid phase in the tube. Fill the tube with nitrogen gas, cover and store it at 4 &#176;C. 
	NOTE: Connect a glass Pasteur pipette to the stream of nitrogen gas to specifically evaporate the desired tube. Additionally, maintain the tube inside a dry block heater for tubes at 37 &#176;C. When the solvent evaporates, fill the tube with nitrogen gas before closing it.</li>
	<li>Add 15 mL of a solution of chloroform:methanol (2:1) to the cellular debris. Leave the tube in constant stirring overnight to extract non-covalent-linked lipids from the mycobacterial cell surface. 
	NOTE: If an orbital shaking platform is not available, constant stirring can be replaced by periodic manual stirring as frequently as possible.</li>
	<li>Let the mixture rest for 1 h. With a Pasteur pipette, recover the organic solvents. Cover a glass funnel with a filter paper and filter the organic solvents and collect them in the same glass tube previously used in step 1.3. Use a nitrogen gas flux to evaporate the liquid phase in the tube. Fill the tube with nitrogen gas, close it and store it again at 4 &#176;C.</li>
</ol>
2. Mycolic acid extraction by acid methanolysis (Figure 2A)
<ol>
	<li>Add 2-5 mL of esterifying solution into a hermetic glass tube with a PTFE liner screw cap. Add 0.2 g of mycobacteria biomass into the glass tube. 
	NOTE: Esterifying solution is formed by mixing 30 mL of methanol, 15 mL of toluene, and 1 mL of sulfuric acid. Mycobacteria cells can be taken from solid cultures or, even from delipidated cells after performing extraction of total non-covalent-linked lipids from mycobacteria (remaining cells after filtering in step 1.6). 
	CAUTION: Toluene is a flammable and extremely hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves). 
	CAUTION: Sulfuric acid is a corrosive and hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves).</li>
	<li>Mix the content by vortexing. Let the mixture stand inside a dry bath at 80 &#176;C overnight.</li>
	<li>Allow the tube to cool until it reaches the room temperature and then add 2 mL of n-hexane to the tube. Mix the contents by vortexing for 30 s and allow the tube to settle until two clear phases appear. 
	CAUTION: n-hexane is a potential flammable, irritant, environmentally damaging, and extremely hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves).</li>
	<li>Recover the upper phase corresponding to the n-hexane phase. Transfer it to a new tube.</li>
	<li>Repeat the step 2.3. Recover the upper phase again and transfer it to the same tube used in step 2.4.</li>
	<li>Evaporate the contents of the tube using a nitrogen gas flux. Fill the tube with nitrogen gas, close it, and store it at 4 &#176;C.</li>
</ol>
3. Mycolic acid extraction by saponification and methylation (Figure 2B)
<ol>
	<li>Scratch 0.2 g of mycobacteria from a solid media and add to a glass tube with a PTFE screw cap.</li>
	<li>Add 2 mL of methanol-benzene solution (80:20) containing 5% potassium hydroxide. Mix the contents by vortexing. Heat the mixture for 3 h at 100 &#176;C. 
	CAUTION: Benzene is a flammable, carcinogenic, and hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves).</li>
	<li>Allow the tube to cool to room temperature. Add 20% sulfuric acid to acidify the samples to achieve pH = 1.</li>
	<li>Add 3 mL of diethyl ether. Gently mix the contents by vortexing.</li>
	<li>Let the two phases form by settling. Recover the diethyl ether phase and transfer to a new tube. Repeat the wash step for a total of three times.</li>
	<li>Wash the diethyl ether extract with 2 mL of distilled water and transfer the upper part corresponding to the diethyl ether to a new tube. Repeat the wash step for a total of three times.</li>
	<li>Add 2 g of anhydrous sodium sulfate over the diethyl ether extract to dry it.</li>
	<li>Filter the suspension. Evaporate the content using a nitrogen gas flux.</li>
	<li>To perform the methylation step, dissolve 3 g of N-nitroso-N-methyl urea in a precooled solution formed by 45 mL of diethyl ether and 9 mL of 40% KOH in distilled water. 
	CAUTION: N-nitroso-N-methylurea is a toxic, irritant, carcinogenic, and hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves).</li>
	<li>Transfer the supernatant (diazomethane) to a new flask cooled in ice containing potassium hydroxide pellets (approximately 30 g). 
	NOTE: If the supernatant is not immediately used, it can be stored at -20 &#176;C for a maximum of 1 h. 
	CAUTION: Potassium hydroxide pellets are an irritant and corrosive substance. This material must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves). 
	CAUTION: Diazomethane is highly toxic and potentially explosive. It must be used in a laminar flow hood with safety glass wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves).</li>
	<li>Add 2 mL of the ether solution containing diazomethane, obtained in step 3.10, into the dried diethyl ether extract that contains mycolic acids, obtained in step 3.8. Incubate for 15 min at room temperature.</li>
	<li>Evaporate the suspension at 40 &#176;C. Fill the tube with nitrogen gas, close it, and store the methylated lipids at 4 &#176;C. 
	&#8203;NOTE: Evaporate the diazomethane from the ether solution under the laminar flow hood, until the ether loses the yellow color.</li>
</ol>
4. Thin layer chromatography (TLC) analysis
<ol>
	<li>Saturate the glass TLC chamber. To do this, cover one of the walls of the TLC chamber with a piece of filter paper and allow it to be in contact with the mobile phase composed by the mixture of solvents. Place the remaining volume of the solvent onto the bottom of the TLC chamber. 
	NOTE: The bottom of the TLC chamber must be covered by at least 1 cm of the mobile phase. In the present experiments, different mobile phases were used to develop the TLCs. They consisted of 85 mL of n-hexane plus 15 mL of diethyl ether; 100 mL of dichloromethane; 90 mL of chloroform, 10 mL of methanol, and 1 mL of water; 30 mL of chloroform, plus 8 mL of methanol, and 1 mL of water; 60 mL of chloroform, plus 35 mL of methanol, and 8 mL of water; 95 mL chloroform plus 5 mL of methanol; and 90 mL of petroleum ether (60-80 &#176;C) plus 10 mL of diethyl ether. 
	NOTE: In the two-dimensional TLC, use n-hexane:acetone (95:5) in the first direction three times, and use a single development with toluene:acetone (97:3) in the second direction to analyze mycolic acid composition. To analyze PIMs, use chloroform:methanol:water (60:30:6) in the first direction once, and use chloroform:acetic acid:methanol:water (40:25:3:6) in the second direction. To analyze PDIM and AG, use petroleum ether (60-80 &#176;C):ethyl acetate (98:2) in the first direction three times, and use a single development with petroleum ether (60-80 &#176;C):acetone (98:2) in the second direction. 
	CAUTION: Diethyl ether is a potentially toxic and hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves). 
	CAUTION: Dichloromethane is a potentially toxic and hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves). 
	CAUTION: Petroleum ether is a potential flammable, environmentally damaging and extremely hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves). 
	CAUTION: Acetic acid is a potential flammable and corrosive substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves). 
	CAUTION: Ethyl acetate is a flammable and hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves). 
	CAUTION: Acetone is a flammable and hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves).</li>
	<li>Close the TLC chamber to saturate it for at least 20 min. Meanwhile, dissolve the lipids present in the glass tube in 0.2-1 mL of chloroform. 
	NOTE: The volume used to dissolve the lipids can be modified depending on the desired or expected concentration of the sample.</li>
	<li>Apply 10 &#181;L of each suspension using a capillary glass tube directly on the TLC plate and let the sample dry for 5 min at room temperature. 
	NOTE: Samples must be applied at the bottom part of the plate leaving 1 cm on each side. Samples must be separated one from another for at least 0.5 cm. Once the sample is applied on the plate, tubes can be evaporated again with nitrogen gas and stored at 4 &#176;C for further use.</li>
	<li>Insert the plate into the saturated TLC chamber containing the mobile phase. Allow the mobile phase to run through the TLC. 
	NOTE: Any movement applied to the TLC chamber affects the running solvent on the plate and affects lipid mobility. In the case of performing two-dimensional TLC, two TLC chambers are required to contain both elution systems.</li>
	<li>Remove the plate from the TLC chamber when the solvent reaches 1 cm distance from the upper end of the plate. Leave the plate under laminar flux until the silica is totally dried. 
	NOTE: In the case of analyzing the mycolic acid composition, using n-hexane and diethyl-ether (85:15),&#160;repeat steps 4.4 and 4.5 two times more, until running the mobile phase three times over the TLC plate.</li>
	<li>Reveal the plate with the required stain; heat the plate if required. 
	NOTE: In the present experiment, 15-20 mL of the following solutions were used to spray the TLC plates: 10% Molybdatophosphoric acid hydrate in ethanol until the plate is bright yellow, followed by heating the plate at 120 &#176;C; 5% in ethanol of&#160;20% &#945;-naphthol in sulfuric acid followed by heating the plate at 120 &#176;C; Molybdenum Blue reagent (1.3% molybdenum oxide in 4.2 M sulfuric acid) until phosphate bands appeared or 1% anthrone in sulfuric acid. 
	CAUTION: Molybdatophosphoric acid hydrate is a flammable and corrosive substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves). 
	CAUTION: Ethanol is a potential flammable and hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves). 
	CAUTION: 1-Naphthol is a flammable, corrosive, and extremely hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves). 
	CAUTION: Molybdenum Blue Spray Reagent is a corrosive, toxic, and extremely hazardous substance. It must be used in a laminar flow hood wearing appropriate personal protective equipment (laboratory coat, protective eyewear, and nitrile gloves).</li>
</ol>

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E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+the+lipids+of+Mycobacterium+tuberculosis.">Analysis of the lipids of Mycobacterium tuberculosis.</a> Mycobacterium tuberculosis Protocols. 54, 229-245 (2001).</li><li>Ojha, A. K., 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=Growth+of+Mycobacterium+tuberculosis+biofilms+containing+free+mycolic+acids+and+harbouring+drug-tolerant+bacteria.">Growth of Mycobacterium tuberculosis biofilms containing free mycolic acids and harbouring drug-tolerant bacteria.</a> Molecular Microbiology. 69 (1), 164-174 (2008).</li><li>Ojha, A. K., Trivelli, X., Guerardel, Y., Kremer, L., Hatfull, G. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enzymatic+hydrolysis+of+trehalose+dimycolate+releases+free+mycolic+acids+during+mycobacterial+growth+in+biofilms.">Enzymatic hydrolysis of trehalose dimycolate releases free mycolic acids during mycobacterial growth in biofilms.</a> The Journal of Biological Chemistry. 285 (23), 17380-17389 (2010).</li><li>Layre, E., 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=Mycolic+acids+constitute+a+scaffold+for+mycobacterial+lipid+antigens+stimulating+CD1-restricted+T+cells.">Mycolic acids constitute a scaffold for mycobacterial lipid antigens stimulating CD1-restricted T cells.</a> Chemistry and Biology. 16 (1), 82-92 (2009).</li><li>Llorens-Fons, M., 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=Trehalose+polyphleates,+external+cell+wall+lipids+in+Mycobacterium+abscessus,+are+associated+with+the+formation+of+clumps+with+cording+morphology,+which+have+been+associated+with+virulence.">Trehalose polyphleates, external cell wall lipids in Mycobacterium abscessus, are associated with the formation of clumps with cording morphology, which have been associated with virulence.</a> Frontiers in Microbiology. 8, (2017).</li><li>Butler, W. R., Guthertz, L. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mycolic+acid+analysis+by+high-performance+liquid+chromatography+for+identification+of+mycobacterium+species.">Mycolic acid analysis by high-performance liquid chromatography for identification of mycobacterium species.</a> Clinical Microbiology Reviews. 14 (4), 704-726 (2001).</li><li>Teramoto, K., 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=Characterization+of+mycolic+acids+in+total+fatty+acid+methyl+ester+fractions+from+Mycobacterium+species+by+high+resolution+MALDI-TOFMS.">Characterization of mycolic acids in total fatty acid methyl ester fractions from Mycobacterium species by high resolution MALDI-TOFMS.</a> Mass Spectrometry. 4 (1), 0035 (2015).</li><li>Sartain, M. J., Dick, D. L., Rithner, C. D., Crick, D. C., Belisle, J. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lipidomic+analyses+of+Mycobacterium+tuberculosis+based+on+accurate+mass+measurements+and+the+novel+"Mtb+LipidDB".">Lipidomic analyses of Mycobacterium tuberculosis based on accurate mass measurements and the novel "Mtb LipidDB".</a> Journal of Lipid Research. 52 (5), 861-872 (2011).</li><li>Li, M., Zhou, Z., Nie, H., Bai, Y., Liu, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+of+chromatography+and+mass+spectrometry+in+lipidomics.">Recent advances of chromatography and mass spectrometry in lipidomics.</a> Analytical and Bioanalytical Chemistry. 399 (1), 243-249 (2011).</li><li>Nahar, A., Baker, A. L., Nichols, D. S., Bowman, J. P., Britz, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+Thin-Layer+Chromatography-Flame+Ionization+Detection+(TLC-FID)+to+total+lipid+quantitation+in+mycolic-acid+synthesizing+Rhodococcus+and+Williamsia+species.">Application of Thin-Layer Chromatography-Flame Ionization Detection (TLC-FID) to total lipid quantitation in mycolic-acid synthesizing Rhodococcus and Williamsia species.</a> International Journal of Molecular Sciences. 21 (5), 1670 (2020).</li></ol>

The authors have nothing to disclose.

A simple protocol considered as the gold standard method for the extraction of noncovalently linked lipid compounds from the mycobacterial cell wall is presented. Further visualization by one- and two-dimensional TLCs from the extracted lipids of four different mycobacteria is shown.
Two consecutive combined mixtures of chloroform and methanol to recover the lipidic content of mycobacterial cells is the most widely used solvent mixture23,24<...

Mycobacterium is a genus that comprises pathogenic and non-pathogenic species, characterized by having a highly hydrophobic and impermeable cell wall formed by their peculiar lipids. Specifically, the mycobacterial cell wall contains mycolic acids, which are &#945;-alkyl and &#946;-hydroxy fatty acids, in which the &#945;-branch is constant in all mycolic acids (except for the length) and the &#946;-chain, called the meromycolate chain, is a long aliphatic chain that may contain different functional chemical groups described along with the literature (&#945;-, &#945;&#39;-, methoxy-, &#954;-, epoxy-, carboxy-, and &#969;-1-methoxy- mycolates), therefore producing seven types of mycolic acids (I-VII)1. Moreover, other lipids with unquestionable importance are also present in the cell wall of mycobacteria species. Pathogenic species such as Mycobacterium tuberculosis, the&#160;causative agent of tuberculosis2 produce specific lipid-based virulence factors such as phthiocerol dimycocerosates (PDIMs), phenolic glycolipid (PGL), di-, tri-, and penta-acyltrehaloses (DAT, TAT, and PAT), or sulfolipids, among others3. Their presence on the mycobacterial surface have been associated with the ability to modify the host immune response and therefore, the evolution and persistence of the mycobacterium inside the host4. For instance, the presence of triacylglycerols (TAG) has been associated with the hypervirulent phenotype of Lineage 2-Beijing sub-lineage of M. tuberculosis, possibly due to its capacity to attenuate the host immune response5,6. Other relevant lipids are lipooligosaccharides (LOSs) present in tuberculous and nontuberculous mycobacteria. In the case of Mycobacterium marinum, the presence of LOSs in its cell wall is related to sliding motility and the ability to form biofilms and interferes with recognition by macrophage pattern recognition receptors, affecting uptake and elimination of the bacteria by host phagocytes7,8. Additionally, the absence or presence of some lipids allows members of the same species to be classified into different morphotypes with virulent or attenuate profiles when interacting with host cells. For instance, the absence of glycopeptidolipids (GPL) in the rough morphotype of Mycobacterium abscessus has been associated with the ability to induce intraphagosomal acidification, and consequently cell apoptosis9, unlike the smooth morphotype that possesses GPLs in their surface. Furthermore, the lipid content of the mycobacterial cell wall is related to the ability to modify the immune response in the host. This is relevant in the context of using some mycobacteria to trigger a protective immune profile against different pathologies10,11,12,13.&#160;It has been demonstrated, for example, that Mycolicibacterium vaccae, a saprophytic mycobacterium, which is currently in phase III clinical trials as an immunotherapeutic vaccine for tuberculosis, display two colonial morphotypes. While the smooth phenotype, that contains a polyester in its surface, triggers a Th2 response, the rough phenotype devoid of the polyester can induce a Th1 profile when it interacts with host immune cells14. The repertoire of lipids present in the mycobacterial cell not only depends on mycobacteria species, but also on the conditions of mycobacterial cultures: time of incubation15,16 or composition of the culture medium17,18. In fact, changes in the culture medium composition affect the antitumor and immunostimulatory activity of M. bovis BCG&#160;and Mycolicibacterium brumae in vitro17. Moreover, the protective immune profile triggered by M. bovis BCG against M. tuberculosis challenge in mice models also depends on the culture media in which M. bovis BCG grows17. These could then be related to the lipid composition of the mycobacteria in each culture condition. For all these reasons, the study of the lipid content of mycobacteria is relevant. A visual procedure to extract and analyze the lipid composition of the mycobacterial cell wall is presented.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Acetic Acid</td>
			<td>Merck</td>
			<td>100063</td>
			<td>CAUTION. Anhydrous for analysis EMSURE&#174; ACS,ISO,Reag. Ph Eur</td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Carlo Erba</td>
			<td>400971N</td>
			<td>CAUTION. ACETONE RPE-ACS-ISO FOR ANALYS ml 1000</td>
		</tr>
		<tr>
			<td>Anthrone</td>
			<td>Merck</td>
			<td>8014610010</td>
			<td>Anthrone for synthesis.</td>
		</tr>
		<tr>
			<td>Benzene</td>
			<td>Carlo Erba</td>
			<td>426113</td>
			<td>CAUTION. Benzene RPE - For analysis - ACS 2.5 l</td>
		</tr>
		<tr>
			<td>Capillary glass tube</td>
			<td>Merck</td>
			<td>BR708709</td>
			<td>BRAND&#174;&#160;disposable BLAUBRAND&#174;&#160;micropipettes, intraMark</td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>Carlo Erba</td>
			<td>412653</td>
			<td>CAUTION. Chloroform RS - For HPLC - Isocratic grade - Stabilized with ethanol 2.5 L</td>
		</tr>
		<tr>
			<td>Dry block heater</td>
			<td>J.P. Selecta</td>
			<td>7471200</td>
			<td></td>
		</tr>
		<tr>
			<td>Dicloromethane</td>
			<td>Carlo Erba</td>
			<td>412622</td>
			<td>CAUTION. Dichloromethane RS - For HPLC - Isocratic grade - Stabilized with amylene 2.5 L</td>
		</tr>
		<tr>
			<td>Diethyl ether</td>
			<td>Carlo Erba</td>
			<td>412672</td>
			<td>CAUTION. Diethyl ether RS - For HPLC - Isocratic grade - Not stabilized 2.5 L</td>
		</tr>
		<tr>
			<td>Ethyl Acetate</td>
			<td>Panreac</td>
			<td>1313181211</td>
			<td>CAUTION. Ethyl acetate (Reag. USP, Ph. Eur.) for analysis, ACS, ISO</td>
		</tr>
		<tr>
			<td>Ethyl Alcohol Absolute</td>
			<td>Carlo Erba</td>
			<td>4146072</td>
			<td>CAUTION. Ethanol absolute anhydrous RPE - For analysis - ACS - Reag. Ph.Eur. - Reag. USP 1 L</td>
		</tr>
		<tr>
			<td>Glass funnel</td>
			<td>VidraFOC</td>
			<td>DURA.2133148 1217/1</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass tube</td>
			<td>VidraFOC</td>
			<td>VFOC.45066A-16125</td>
			<td>Glass tube with PTFE recovered cap</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Carlo Erba</td>
			<td>412722</td>
			<td>CAUTION. Methanol RS - For HPLC - GOLD - Ultragradient grade 2.5 L</td>
		</tr>
		<tr>
			<td>Molybdatophosphoric acid hydrate</td>
			<td>Merck</td>
			<td>51429-74-4</td>
			<td>CAUTION.</td>
		</tr>
		<tr>
			<td>Molybdenum Blue Spray Reagent, 1.3%</td>
			<td>Sigma</td>
			<td>M1942-100ML</td>
			<td>CAUTION.</td>
		</tr>
		<tr>
			<td>n-hexane</td>
			<td>Carlo Erba</td>
			<td>446903</td>
			<td>CAUTION. n-Hexane 99% RS - ATRASOL - For traces analysis 2.5 L</td>
		</tr>
		<tr>
			<td>n-nitroso-n-methylurea</td>
			<td>Sigma</td>
			<td>N4766</td>
			<td>CAUTION</td>
		</tr>
		<tr>
			<td>Orbital shaking platform</td>
			<td>DDBiolab</td>
			<td>995018</td>
			<td>NB-205L benchtop shaking incubator</td>
		</tr>
		<tr>
			<td>Petroleum ether (60-80&#186;C)</td>
			<td>Carlo Erba</td>
			<td>427003</td>
			<td>CAUTION. Petroleum ether 60 - 80&#176;C RPE - For analysis 2.5 L</td>
		</tr>
		<tr>
			<td>Sprayer</td>
			<td>VidraFOC</td>
			<td>712/1</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium sulphate anhydrous</td>
			<td>Merck</td>
			<td>238597</td>
			<td></td>
		</tr>
		<tr>
			<td>Sulfuric acid 95-97%</td>
			<td>Merck</td>
			<td>1007311000</td>
			<td>CAUTION. Sulfuric acid 95-97%</td>
		</tr>
		<tr>
			<td>TLC chamber</td>
			<td>Merck</td>
			<td>Z204226-1EA</td>
			<td>Rectangular TLC developing tanks, complete L &#215; H &#215; W 22 cm &#215; 22 cm &#215; 10 cm</td>
		</tr>
		<tr>
			<td>TLC plate</td>
			<td>Merck</td>
			<td>1057210001</td>
			<td>TLC SilicaGel 60- 20x20 cm x 25 u</td>
		</tr>
		<tr>
			<td>TLC Plate Heater</td>
			<td>CAMAG</td>
			<td>223306</td>
			<td>CAMAG TLC Plat Heater III</td>
		</tr>
		<tr>
			<td>Toluene</td>
			<td>Carlo Erba</td>
			<td>488551</td>
			<td>CAUTION. Toluene RPE - For analysis - ISO - ACS - Reag.Ph.Eur. - Reag.USP 1 L</td>
		</tr>
		<tr>
			<td>Vortex</td>
			<td>Fisher Scientific</td>
			<td>10132562</td>
			<td>IKA&#160;Agitador IKA v&#243;rtex 3</td>
		</tr>
		<tr>
			<td>1-naphthol</td>
			<td>Sigma-Aldrich</td>
			<td>102269427</td>
			<td>CAUTION.</td>
		</tr>
	</tbody>
</table>

analysis of the lipid composition of mycobacteria by thin layer chromatography

Mycobacteria species can differ from one another in the rate of growth, presence of pigmentation, the colony morphology displayed on solid media, as well as other phenotypic characteristics. However, they all have in common the most relevant character of mycobacteria: its unique and highly hydrophobic cell wall. Mycobacteria species contain a membrane-covalent linked complex that includes arabinogalactan, peptidoglycan, and long-chains of mycolic acids with types that differ between mycobacteria species. Additionally, mycobacteria can also produce lipids that are located, non-covalently linked, on their cell surfaces, such as phthiocerol dimycocerosates (PDIM), phenolic glycolipids (PGL), glycopeptidolipids (GPL), acyltrehaloses (AT), or phosphatidil-inositol mannosides (PIM), among others. Some of them are considered virulence factors in pathogenic mycobacteria, or critical antigenic lipids in host-mycobacteria interaction. For these reasons, there is a significant interest in the study of mycobacterial lipids due to their application in several fields, from understanding their role in the pathogenicity of mycobacteria infections, to a possible implication as immunomodulatory agents for the treatment of infectious diseases and other pathologies such as cancer. Here, a simple approach to extract and analyze the total lipid content and the mycolic acid composition of mycobacteria cells grown in a solid medium using mixtures of organic solvents is presented. Once the lipid extracts are obtained, thin-layer chromatography (TLC) is performed to monitor the extracted compounds. The example experiment is performed with four different mycobacteria: the environmental fast-growing Mycolicibacterium brumae and Mycolicibacterium fortuitum, the attenuated slow-growing Mycobacterium bovis bacillus Calmette-Gu&#233;rin (BCG), and the opportunistic pathogen fast-growing Mycobacterium abscessus, demonstrating that methods shown in the present protocol can be used to a wide range of mycobacteria.

With the aim of showing a wide range of lipids present in different mycobacteria species, M. bovis BCG was selected as it is rough and slow-growing mycobacteria. The rough and fast-growing M. fortuitum and M. brumae were added in the procedure and, finally, the smooth morphotype of M. abscessus was also included. These four species permit us to visualize a broad spectrum of mycobacteria-derived lipids such as acyltrehaloses (AT), GPLs, PDIM, PGL, PIM, TDM, and TMM. Moreover, all four s...

Watch this Scientific Journal Video about Analysis of the Lipid Composition of Mycobacteria by Thin Layer Chromatography at JoVE.com

Analysis of the Lipid Composition of Mycobacteria by Thin Layer Chromatography

A protocol is presented to extract the total lipid content of the cell wall of a wide range of mycobacteria. Moreover, extraction and analytical protocols of the different types of mycolic acids are shown. A thin-layer chromatographic protocol to monitor these mycobacterial compounds is also provided.

Mycobacteria species can differ from one another in the rate of growth, presence of pigmentation, the colony morphology displayed on solid media, as well ...

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7.6K Views.  Universitat Autònoma de Barcelona. A protocol is presented to extract the total lipid content of the cell wall of a wide range of mycobacteria. Moreover, extraction and analytical protocols of the different types of mycolic acids are shown. A thin-layer chromatographic protocol to monitor these mycobacterial compounds is also provided.

Video: Analysis of the Lipid Composition of Mycobacteria by Thin Layer Chromatography

Separation of Single-stranded DNA, Double-stranded DNA and RNA from an Environmental Viral Community Using Hydroxyapatite Chromatography

Viruses, particularly bacteriophages (phages), are the most numerous biological entities on Earth1,2. Viruses modulate host cell abundance and diversity, contribute to the cycling of nutrients, alter host cell phenotype, and influence the evolution of both host cell and viral communities through the lateral transfer of genes 3. Numerous studies have highlighted the staggering genetic diversity of viruses and their functional potential in a variety of natural environments. 
Metagenomic techniques have been used to study the taxonomic diversity and functional potential of complex viral assemblages whose members contain single-stranded DNA (ssDNA), double-stranded DNA (dsDNA) and RNA genotypes 4-9. Current library construction protocols used to study environmental DNA-containing or RNA-containing viruses require an initial nuclease treatment in order to remove nontargeted templates 10. However, a comprehensive understanding of the collective gene complement of the virus community and virus diversity requires knowledge of all members regardless of genome composition. Fractionation of purified nucleic acid subtypes provides an effective mechanism by which to study viral assemblages without sacrificing a subset of the community&#x2019;s genetic signature. 
Hydroxyapatite, a crystalline form of calcium phosphate, has been employed in the separation of nucleic acids, as well as proteins and microbes, since the 1960s11. By exploiting the charge interaction between the positively-charged Ca2+ ions of the hydroxyapatite and the negatively charged phosphate backbone of the nucleic acid subtypes, it is possible to preferentially elute each nucleic acid subtype independent of the others. We recently employed this strategy to independently fractionate the genomes of ssDNA, dsDNA and RNA-containing viruses in preparation of DNA sequencing 12. Here, we present a method for the fractionation and recovery of ssDNA, dsDNA and RNA viral nucleic acids from mixed viral assemblages using hydroxyapatite chromotography.

We describe an efficient method to separate single-stranded DNA, double-stranded DNA and RNA molecules from environmental viral communities. Nucleic acids are fractionated using hydroxyapatite chromatography with increasing concentrations of phosphate-containing buffers. This method permits the isolation of all viral nucleic acid types from environmental samples.

Viruses, particularly bacteriophages (phages), are the most numerous biological entities on Earth1,2.  Viruses modulate host cell abundance and diversity, ...

A Functional Whole Blood Assay to Measure Viability of Mycobacteria, using Reporter-Gene Tagged BCG or M.Tb (BCG lux/M.Tb lux)

Functional assays have long played a key role in measuring of immunogenicity of a given vaccine. This is conventionally expressed as serum bactericidal titers. Studies of serum bactericidal titers in response to childhood vaccines have enabled us to develop and validate cut-off levels for protective immune responses and such cut-offs are in routine use. No such assays have been taken forward into the routine assessment of vaccines that induce primarily cell-mediated immunity in the form of effector T cell responses, such as TB vaccines. In the animal model, the performance of a given vaccine candidate is routinely evaluated in standardized bactericidal assays, and all current novel TB-vaccine candidates have been subjected to this step in their evaluation prior to phase 1 human trials. The assessment of immunogenicity and therefore likelihood of protective efficacy of novel anti-TB vaccines should ideally undergo a similar step-wise evaluation in the human models now, including measurements in bactericidal assays.
Bactericidal assays in the context of tuberculosis vaccine research are already well established in the animal models, where they are applied to screen potentially promising vaccine candidates. Reduction of bacterial load in various organs functions as the main read-out of immunogenicity. However, no such assays have been incorporated into clinical trials for novel anti-TB vaccines to date.
Although there is still uncertainty about the exact mechanisms that lead to killing of mycobacteria inside human macrophages, the interaction of macrophages and T cells with mycobacteria is clearly required. The assay described in this paper represents a novel generation of bactericidal assays that enables studies of such key cellular components with all other cellular and humoral factors present in whole blood without making assumptions about their relative individual contribution. The assay described by our group uses small volumes of whole blood and has already been employed in studies of adults and children in TB-endemic settings. We have shown immunogenicity of the BCG vaccine, increased growth of mycobacteria in HIV-positive patients, as well as the effect of anti-retroviral therapy and Vitamin D on mycobacterial survival in vitro. Here we summarise the methodology, and present our reproducibility data using this relatively simple, low-cost and field-friendly model.
Note: Definitions/Abbreviations
BCG lux = M. bovis BCG, Montreal strain, transformed with shuttle plasmid pSMT1 carrying the luxAB genes from Vibrio harveyi, under the control of the mycobacterial GroEL (hsp60) promoter. 
CFU = Colony Forming Unit (a measure of mycobacterial viability).

A Functional Whole Blood Assay to Measure Viability of Mycobacteria, using Reporter-Gene Tagged BCG or M.Tb BCG lux/M.Tb lux

We describe an alternative approach to the enumeration of mycobacteria in vitro, which uses reporter-gene tagged mycobacteria instead of colony-forming units (CFU). &#x201C;Survival&#x201D; of organisms as well as host response-markers are measured simultaneously, providing a low-cost, versatile and functional system for studies of host/pathogen interactions in the context of tuberculosis.

Functional assays have long played a key role in measuring of immunogenicity of a given vaccine. This is conventionally expressed as serum bactericidal ...

A Microscopic Phenotypic Assay for the Quantification of Intracellular Mycobacteria Adapted for High-throughput/High-content Screening

Despite the availability of therapy and vaccine, tuberculosis (TB) remains one of the most deadly and widespread bacterial infections in the world. Since several decades, the sudden burst of multi- and extensively-drug resistant strains is a serious threat for the control of tuberculosis. Therefore, it is essential to identify new targets and pathways critical for the causative agent of the tuberculosis, Mycobacterium tuberculosis (Mtb) and to search for novel chemicals that could become TB drugs. One approach is to set&#160;up methods suitable for the genetic and chemical screens of large scale libraries enabling the search of a needle in a haystack. To this end, we developed a phenotypic assay relying on the detection of fluorescently labeled Mtb within fluorescently labeled host&#160;cells using automated confocal microscopy. This in vitro assay allows an image based quantification of the colonization process of Mtb&#160;into the host and was optimized for the 384-well microplate format, which is proper for screens of siRNA-, chemical compound- or Mtb mutant-libraries. The images are then processed for multiparametric analysis, which provides read&#160;out inferring on the pathogenesis of Mtb&#160;within host cells.

Here, we describe a phenotypic assay applicable to the High-throughput/High-content screens of small-interfering synthetic RNA (siRNA), chemical compound, and Mycobacterium tuberculosis mutant libraries. This method relies on the detection of fluorescently labeled Mycobacterium tuberculosis within fluorescently labeled host&#160;cell using automated confocal microscopy.

Despite the availability of therapy and vaccine, tuberculosis (TB) remains one of the most deadly and widespread bacterial infections in the world. Since ...

Analysis of the Epithelial Damage Produced by Entamoeba histolytica Infection

Entamoeba histolytica is the causative agent of human amoebiasis, a major cause of diarrhea and hepatic abscess in tropical countries. Infection is initiated by interaction of the pathogen with intestinal epithelial cells. This interaction leads to disruption of intercellular structures such as tight junctions (TJ). TJ ensure sealing of the epithelial layer to separate host tissue from gut lumen. Recent studies provide evidence that disruption of TJ by the parasitic protein EhCPADH112 is a prerequisite for E. histolytica invasion that is accompanied by epithelial barrier dysfunction. Thus, the analysis of molecular mechanisms involved in TJ disassembly during E. histolytica invasion is of paramount importance to improve our understanding of amoebiasis pathogenesis. This article presents an easy model that allows the assessment of initial host-pathogen interactions and the parasite invasion potential. Parameters to be analyzed include transepithelial electrical resistance, interaction of EhCPADH112 with epithelial surface receptors, changes in expression and localization of epithelial junctional markers and localization of parasite molecules within epithelial cells.

Analysis of the Epithelial Damage Produced by Entamoeba histolytica Infection

Human infection by Entamoeba histolytica leads to amoebiasis, a major cause of diarrhea in tropical countries. Infection is initiated by pathogen interactions with intestinal epithelial cells, provoking the opening of cell-cell contacts and consequently diarrhea, sometimes followed by liver infection. This article provides a model to assess the early host-pathogen interactions to improve our understanding of amoebiasis pathogenesis.

Entamoeba histolytica is the causative agent of human amoebiasis, a major cause of diarrhea and hepatic abscess in tropical countries. Infection is ...

Rapid Analysis of Chromosome Aberrations in Mouse B Lymphocytes by PNA-FISH

Defective DNA repair leads to increased genomic instability, which is the root cause of mutations that lead to tumorigenesis. Analysis of the frequency and type of chromosome aberrations in different cell types allows defects in DNA repair pathways to be elucidated. Understanding mammalian DNA repair biology has been greatly helped by the production of mice with knockouts in specific genes. The goal of this protocol is to quantify genomic instability in mouse B lymphocytes. Labeling of the telomeres using PNA-FISH probes (peptide nucleic acid - fluorescent in situ hybridization) facilitates the rapid analysis of genomic instability in metaphase chromosome spreads. B cells have specific advantages relative to fibroblasts, because they have normal ploidy and a higher mitotic index. Short-term culture of B cells therefore enables precise measurement of genomic instability in a primary cell population which is likely to have fewer secondary genetic mutations than what is typically found in transformed fibroblasts or patient cell lines.

DNA repair pathways are essential for maintenance of genomic integrity and preventing mutation and cancer. The goal of this protocol is to quantify genomic instability by direct observation of chromosome aberrations in metaphase spreads from mouse B cells using fluorescent in situ hybridization (FISH) for telomeric DNA repeats.

Defective DNA repair leads to increased genomic instability, which is the root cause of mutations that lead to tumorigenesis. Analysis of the frequency ...

Visualization of the Charcoal Agar Resazurin Assay for Semi-quantitative, Medium-throughput Enumeration of Mycobacteria

There is an urgent need to discover and progress anti-infectives that shorten the duration of tuberculosis (TB) treatment. Mycobacterium tuberculosis, the etiological agent of TB, is refractory to rapid and lasting chemotherapy due to the presence of bacilli exhibiting phenotypic drug resistance. The charcoal agar resazurin assay (CARA) was developed as a tool to characterize active molecules discovered by high-throughput screening campaigns against replicating and non-replicating M. tuberculosis. Inclusion of activated charcoal in bacteriologic agar medium helps mitigate the impact of compound carry-over, and eliminates the requirement to pre-dilute cells prior to spotting on CARA microplates. After a 7-10 day incubation period at 37 &#176;C, the reduction of resazurin by mycobacterial microcolonies growing on the surface of CARA microplate wells permits semi-quantitative assessment of bacterial numbers via fluorometry. The CARA detects approximately a 2-3 log10 difference in bacterial numbers and predicts a minimal bactericidal concentration leading to &#8805;99% bacterial kill (MBC&#8805;99). The CARA helps determine whether a molecule is active on bacilli that are replicating, non-replicating, or both. Pilot experiments using the CARA facilitate the identification of which concentration of test agent and time of compound exposure require further evaluation by colony forming unit (CFU) assays. In addition, the CARA can predict if replicating actives are bactericidal or bacteriostatic.

The charcoal agar resazurin assay (CARA) is a semi-quantitative, medium-throughput method to assess activity of test agents against mycobacteria that are replicating, non-replicating, or both. The CARA permits rapid evaluation of time- and concentration-dependent activity and identifies parameters to pursue by colony forming unit (CFU) assays.

There is an urgent need to discover and progress anti-infectives that shorten the duration of tuberculosis (TB) treatment. Mycobacterium tuberculosis, the ...

Paraffin Embedding and Thin Sectioning of Microbial Colony Biofilms for Microscopic Analysis

Sectioning via paraffin embedding is a broadly established technique in eukaryotic systems. Here we provide a method for the fixation, embedding, and sectioning of intact microbial colony biofilms using perfused paraffin wax. To adapt this method for use on colony biofilms, we developed techniques for maintaining each sample on its growth substrate and laminating it with an agar overlayer, and added lysine to the fixative solution. These optimizations improve sample retention and preservation of micromorphological features. Samples prepared in this manner are amenable to thin sectioning and imaging by light, fluorescence, and transmission electron microscopy. We have applied this technique to colony biofilms of Pseudomonas aeruginosa, Pseudomonas synxantha, Bacillus subtilis, and Vibrio cholerae. The high level of detail visible in samples generated by this method, combined with reporter strain engineering or the use of specific dyes, can provide exciting insights into the physiology and development of microbial communities.

We describe fixation, paraffin embedding, and thin sectioning techniques for microbial colony biofilms. In prepared samples, biofilm substructure and reporter expression patterns can be visualized by microscopy.

Sectioning via paraffin embedding is a broadly established technique in eukaryotic systems. Here we provide a method for the fixation, embedding, and ...

Characterization of Human Monocyte Subsets by Whole Blood Flow Cytometry Analysis

Monocytes are key contributors in various inflammatory disorders and alterations to these cells, including their subset proportions and functions, can have pathological significance. An ideal method for examining alterations to monocytes is whole blood flow cytometry as the minimal handling of samples by this method limits artifactual cell activation. However, many different approaches are taken to gate the monocyte subsets leading to inconsistent identification of the subsets between studies. Here we demonstrate a method using whole blood flow cytometry to identify and characterize human monocyte subsets (classical, intermediate, and non-classical). We outline how to prepare the blood samples for flow cytometry, gate the subsets (ensure contaminating cells have been removed), and determine monocyte subset expression of surface markers &#8212; in this example M1 and M2 markers. This protocol can be extended to other studies that require a standard gating method for assessing monocyte subset proportions and monocyte subset expression of other functional markers.

Here we present a protocol for characterizing monocyte subsets by whole blood flow cytometry. This includes outlining how to gate the subsets and assess their expression of surface markers and giving an example of the assessment of the expression of M1 (inflammatory) and M2 markers (anti-inflammatory).

Monocytes are key contributors in various inflammatory disorders and alterations to these cells, including their subset proportions and functions, can ...

Analysis of Lipid Droplet Content in Fission and Budding Yeasts using Automated Image Processing

Lipid metabolism and its regulation are of interest to both basic and applied life sciences and biotechnology. In this regard, various yeast species are used as models in lipid metabolic research or for industrial lipid production. Lipid droplets are highly dynamic storage bodies and their cellular content represents a convenient readout of the lipid metabolic state. Fluorescence microscopy is a method of choice for quantitative analysis of cellular lipid droplets, as it relies on widely available equipment and allows analysis of individual lipid droplets. Furthermore, microscopic image analysis can be automated, greatly increasing overall analysis throughput. Here, we describe an experimental and analytical workflow for automated detection and quantitative description of individual lipid droplets in three different model yeast species: the fission yeasts Schizosaccharomyces pombe and Schizosaccharomyces japonicus, and the budding yeast Saccharomyces cerevisiae. Lipid droplets are visualized with BODIPY 493/503, and cell-impermeable fluorescent dextran is added to the culture media to help identify cell boundaries. Cells are subjected to 3D epifluorescence microscopy in green and blue channels and the resulting z-stack images are processed automatically by a MATLAB pipeline. The procedure outputs rich quantitative data on cellular lipid droplet content and individual lipid droplet characteristics in a tabular format suitable for downstream analyses in major spreadsheet or statistical packages. We provide example analyses of lipid droplet content under various conditions that affect cellular lipid metabolism.

Here, we present a MATLAB implementation of automated detection and quantitative description of lipid droplets in fluorescence microscopy images of fission and budding yeast cells.

Lipid metabolism and its regulation are of interest to both basic and applied life sciences and biotechnology. In this regard, various yeast species are ...

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.

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) ...