The authors would like to thank Nathan Johnson for his assistance in preparing the figures. This research was supported by the Pan-omics Program that is funded by the U.S. Department of Energy&#39;s Office of Biological and Environmental Research (Genomic Science Program), the Microbiomes in Transition (MinT) Laboratory Directed Research Development Initiative at the Pacific Northwest National Laboratory, as well as the National Institutes of Health National Institute of Environmental Health Sciences (R01 ES022190) and NIH (P42 ES027704). KEBJ would like to thank R21 HD084788 for financial support to develop and validate novel multi-omic extraction techniques. This work was performed in the W. R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a DOE national scientific user facility at the Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated by Battelle for the DOE under Contract DE-AC06-76RL01830.

NOTE: Very wet soils can be lyophilized prior to extraction without detriment to the effectiveness of the extraction. Wet soil can also be used but should be considered when adding reagents at specific ratios.
NOTE: It is recommended to use 20 g of dry soil weight per extraction, which must be split between two 50 mL tubes (maximum of 10 g soil per 50 mL tube). Extractions can be scaled up or down dependent upon available sample.
NOTE: Dry soil samples can be sieved...

<ol>
	<li>Hultman, 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=Multi-omics+of+permafrost,+active+layer+and+thermokarst+bog+soil+microbiomes.">Multi-omics of permafrost, active layer and thermokarst bog soil microbiomes.</a> Nature. 521, 208-212 (2015).</li><li>White, R. 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=Moleculo+long-read+sequencing+facilitates+assembly+and+genomic+binning+from+complex+soil+metagenomes.">Moleculo long-read sequencing facilitates assembly and genomic binning from complex soil metagenomes.</a> mSystems. 1, (2016).</li><li>White, R. A., Callister, S. J., Moore, R. J., Baker, E. S., Jansson, J. 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It is important to note that not all laboratories will have the same available equipment so certain methods, for example the lysis step, can be adapted. Here we use vortexing and sonicating, however the use of a large 50 mL bead beater would work. If a lyophilizer with a collector temperature capable of -105 &#176;C is not available, then samples can be dried under a nitrogen stream. Also soil types vary greatly and can include sand, silt, clay, peat, and loam (etc.), and they can also vary based on pH, salinity...

Evaluating soil microbial communities has important implications for understanding carbon cycling and climate change. Recent studies have however highlighted difficulties, such as the lack of sequenced genomes for microbiota in various soil types and the unknown function of many of the proteins detected. These challenges result due to soil being the most complex microbial community known to date1,2,3. Multi-omic analyses, which combine results from metagenomic, metatranscriptomic, metaproteomic, metabolomic, and lipidomic studies, have recently been implemented in numerous soil studies to gain a greater understanding into the microbes present, while obtaining comprehensive information about the molecular changes taking place due to environmental perturbations1,4,5. One challenge with multi-omic studies is that the mass spectrometry (MS)-based metaproteomic, metabolomic, and lipidomic measurements typically require a specific extraction process for each omic to be MS compatible6,7,8,9. These precise procedures make their implementation extremely difficult or impossible when only a limited quantity of sample is available. These challenges have prompted us to investigate a simultaneous metabolite, protein, and lipid extraction (MPLEx) method capable of using smaller sample volumes or masses, improving accuracy, and providing faster sample preparations for all three analyses10. To date, there are no alternate soil extraction procedures that can achieve all of these goals.
To enable global multi-omic analyses of a single soil sample, an organic solvent extraction protocol based upon chloroform, methanol, and water separations was utilized10. This method was originally developed for total lipid extractions9,11 and more recently was amended for the simultaneous extraction of metabolites, proteins, and lipids from a single sample12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30, enabling less sample quantity and experimental variability10. In the MPLEx protocol, chloroform is not miscible with water, which provides the basis for the triphasic chemical separation of sample constituents into distinct fractions. The top aqueous phase therefore contains the hydrophilic metabolites, followed by a protein disk, and then a lipid layer in the bottom chloroform phase (Figure 1). When MPLEx is applied to most soils, particulate debris accumulates at the very bottom of the sampling tubes and can be discarded after all layers are collected. Each soil type can be different, however, and in highly organic soil such as peat, the soil debris stays in the middle layer and does not fall to the bottom of the sampling tube. MPLEx provides several advantages when isolating multiple molecule types from the same sample such as 1) smaller sample quantities can be used for multi-omic analyses, 2) multi-omic extractions from the same sample decrease overall experimental variability, and 3) greater numbers of samples can be prepared much faster for higher throughput studies10. Together these benefits are vital for providing better measurement capabilities for evaluating soil samples and their complex microbial communities.

<table>
	<tbody>
		<tr>
			<td>Chloroform</td>
			<td>Sigma-Aldrich</td>
			<td>650498</td>
			<td>Stored at -20&#176;C !Caution chloroform has acute potential health effects, skin irritation and possible chemical burns, irritation to the respiratory system, may affect the kidneys, liver, heart. Wear suitable protective glasses, clothing and gloves, work in a fume hood.</td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Sigma-Aldrich</td>
			<td>34860</td>
			<td>Stored at -20&#176;C !Caution Methanol may cause respiratory tract, skin and eye irritation, may damage the nerves, kidneys and liver. Wear suitable protective glasses, clothing and gloves, work in a fume hood.</td>
		</tr>
		<tr>
			<td>Purified water from Millipore</td>
			<td>Milli-Q</td>
			<td></td>
			<td>Water purification system.</td>
		</tr>
		<tr>
			<td>Sodium dodecyl sulfate</td>
			<td>Sigma-Aldrich</td>
			<td>L6026</td>
			<td>!Caution SDS causes acute toxicity and is flammable. It is a skin, eye and airway irritant. Wear gloves and safety glasses.</td>
		</tr>
		<tr>
			<td>Soil protein extraction kit</td>
			<td>MoBio, NoviPure Soil Protein Extraction Kit, Qiagen</td>
			<td>30000-20</td>
			<td></td>
		</tr>
		<tr>
			<td>DL-dithiothreitol</td>
			<td>Sigma-Aldrich</td>
			<td>43815</td>
			<td></td>
		</tr>
		<tr>
			<td>1M Trizma HCL</td>
			<td>Sigma-Aldrich</td>
			<td>T2694</td>
			<td></td>
		</tr>
		<tr>
			<td>Trichloroacetic acid</td>
			<td>Sigma-Aldrich</td>
			<td>T0699</td>
			<td>!Caution TCA is caustic, toxic and may cause skin burns. Wear gloves and safety glasses.</td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Sigma-Aldrich</td>
			<td>650501</td>
			<td>Stored at -20&#176;C !Caution Acetone may cause respiratory tract and skin and eye irritation. Flammable liquid and vapor. Wear safety glasses gloves and a lab coat, work in a fume hood.</td>
		</tr>
		<tr>
			<td>Urea</td>
			<td>Sigma-Aldrich</td>
			<td>208884</td>
			<td>!Caution Urea is an eye and skin irritant, use gloves and safety glasses</td>
		</tr>
		<tr>
			<td>Ammonium bicarbonate</td>
			<td>Fluka</td>
			<td>09830</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin</td>
			<td>Promega</td>
			<td>V528A</td>
			<td>20&#181;g vials</td>
		</tr>
		<tr>
			<td>Bicinchoninic acid protein assay kit</td>
			<td>Pierce</td>
			<td>23227</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium Formate</td>
			<td>Sigma-Aldrich</td>
			<td>09735</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetonitrile</td>
			<td>Sigma-Aldrich</td>
			<td>34998</td>
			<td>!Caution Acetonitrile is a skin and eye irritant. Highly flammable. Wear gloves and safety glasses. Work in a fume hood.</td>
		</tr>
		<tr>
			<td>Trifluoroacetic acid</td>
			<td>Sigma-Aldrich</td>
			<td>T6508</td>
			<td>!Caution TFA is extremely hazardous in case of skin contact, eye contact, ingestion and inhalation. May produce tissue damage particularly on mucous membranes of eyes, mouth and respiratory tract. Skin contact may produce burns. Wear gloves, lab coat, safety glasses and work in a fume hood.</td>
		</tr>
		<tr>
			<td>Methoxyamine hydrochloride</td>
			<td>Sigma-Aldrich</td>
			<td>226904</td>
			<td>!Caution Methoxyamine hydrochloride causes severe burns and serious damage to eyes, may cause sensitization by skin contact. Wear safety glasses, gloves and lab coat, work in a fume hood.</td>
		</tr>
		<tr>
			<td>Pyridine</td>
			<td>Sigma-Aldrich</td>
			<td>270970</td>
			<td>!Caution Pyridine can cause skin and eye irritation, central nervous system depression. Vapor may cause flash fire. Wear safety glasses, gloves and lab coat, work in a fume hood.</td>
		</tr>
		<tr>
			<td>N-Methyl-N-(trimethylsilyl)trifluoroacetamide with 1% trimethylchlorosilane</td>
			<td>Sigma-Aldrich</td>
			<td>69478</td>
			<td>!Caution MSTFA + 1% TMCS can cause skin corrosion, serious eye damage and specific target organ toxicity. Flammable liquid and vapor. Wear safety glasses, gloves and lab coat, work in a fume hood.</td>
		</tr>
		<tr>
			<td>Potassium chloride</td>
			<td>Sigma-Aldrich</td>
			<td>P9541</td>
			<td></td>
		</tr>
		<tr>
			<td>Milli-Q water purification system</td>
			<td>Millipore</td>
			<td></td>
			<td>model MPGP04001</td>
		</tr>
		<tr>
			<td>Vortex</td>
			<td>Scientific Industries</td>
			<td>SI-0236</td>
			<td>Vortex Genie 2</td>
		</tr>
		<tr>
			<td>Probe sonicator</td>
			<td>FisherBrand</td>
			<td></td>
			<td>model FB505</td>
		</tr>
		<tr>
			<td>Refrigerated centrifuge</td>
			<td>Eppendorf</td>
			<td></td>
			<td>model 5810R</td>
		</tr>
		<tr>
			<td>50mL tube swinging bucket rotor</td>
			<td>Eppendorf</td>
			<td>A-4-44</td>
			<td></td>
		</tr>
		<tr>
			<td>50mL fixed angle rotor</td>
			<td>Eppendorf</td>
			<td>FA-45-6-30</td>
			<td></td>
		</tr>
		<tr>
			<td>Balance</td>
			<td>OHAUS</td>
			<td></td>
			<td>model V22PWE150IT</td>
		</tr>
		<tr>
			<td>Serological pipette controller</td>
			<td>Eppendorf</td>
			<td>12-654-100</td>
			<td></td>
		</tr>
		<tr>
			<td>10mL, 25mL glass serological pipettes</td>
			<td>FisherBrand</td>
			<td>13-678-27F, 13-678-36D</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermomixer with Thermotop</td>
			<td>Eppendorf</td>
			<td>5382000015, 5308000003</td>
			<td></td>
		</tr>
		<tr>
			<td>0.9 &#8211; 2.0 mm blend stainless steel beads</td>
			<td>NextAdvance</td>
			<td>SSB14B</td>
			<td></td>
		</tr>
		<tr>
			<td>0.15 mm garnet beads</td>
			<td>MoBio</td>
			<td>13122-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic stir plate</td>
			<td>FisherBrand</td>
			<td>11-100-16SH</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic stir bar</td>
			<td>FisherBrand</td>
			<td>14512130</td>
			<td></td>
		</tr>
		<tr>
			<td>pH paper strips, pH range 0&#8211;14</td>
			<td>FisherBrand</td>
			<td>M95903</td>
			<td></td>
		</tr>
		<tr>
			<td>15mL, 50mL conical polypropylene centrifuge tube</td>
			<td>Genesee Scientific</td>
			<td>21-103 21-108</td>
			<td>chloroform compatible</td>
		</tr>
		<tr>
			<td>50mL vortex attachment</td>
			<td>MoBio</td>
			<td>13000-V1-50</td>
			<td></td>
		</tr>
		<tr>
			<td>Ice bucket</td>
			<td>FisherBrand</td>
			<td>02-591-44</td>
			<td></td>
		</tr>
		<tr>
			<td>27.25x70mm glass vials</td>
			<td>FisherBrand</td>
			<td>03-339-22K</td>
			<td></td>
		</tr>
		<tr>
			<td>Breathe Easier plate membranes</td>
			<td>Midwest Scientific</td>
			<td>BERM-2000</td>
			<td></td>
		</tr>
		<tr>
			<td>Alcohol wipes</td>
			<td>Diversified Biotech</td>
			<td>BPWP-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Heater shaker incubator</td>
			<td>Benchmark, Incu-Shaker Mini</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Analog rotisserie tube rotator</td>
			<td>SoCal BioMed, LLC</td>
			<td>82422001</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter-Aided-Sample-Prep kit</td>
			<td>FASP; Expedeon</td>
			<td>44250</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate reader</td>
			<td>Biotek, EPOCH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>-20 Degree Celsius Freezer</td>
			<td>Fisher</td>
			<td>13986149</td>
			<td></td>
		</tr>
		<tr>
			<td>-80 Degree Celsius Freezer</td>
			<td>Stirling Ultracold</td>
			<td>SU78OUE</td>
			<td></td>
		</tr>
		<tr>
			<td>Q-Exactive ion trap mass spectrometer</td>
			<td>Thermo Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Agilent 7890A gas chromatograph coupled with a single quadrupole 5975C mass spectrometer</td>
			<td>Agilent Technologies, Inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>LTQ-Orbitrap Velo</td>
			<td>Thermo Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Waters NanoEquityTM UPLC system</td>
			<td>Millford, MA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>250mL media bottle</td>
			<td>FisherBrand</td>
			<td>1395-250</td>
			<td></td>
		</tr>
		<tr>
			<td>Waters vial</td>
			<td>Waters</td>
			<td>186002805</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass MS sample vial and inserts</td>
			<td>MicroSolv</td>
			<td>9502S-WCV, 9502S-02ND</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass HPLC vial and snap caps</td>
			<td>MicroSolv</td>
			<td>9512C-0DCV, 9502C-10C-B</td>
			<td></td>
		</tr>
		<tr>
			<td>HPLC 96-well plate</td>
			<td>Agilent</td>
			<td>5042-6454</td>
			<td></td>
		</tr>
		<tr>
			<td>Large glass vial 27.25x70mm</td>
			<td>FisherBrand</td>
			<td>03-339-22K</td>
			<td></td>
		</tr>
		<tr>
			<td>Lyophilizer</td>
			<td>Labconco</td>
			<td>7934021</td>
			<td></td>
		</tr>
		<tr>
			<td>Polished stainless steel flat head spatula</td>
			<td>Spoonula; FisherBrand</td>
			<td>14-375-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Kim wipes</td>
			<td>Kimberly-Clark</td>
			<td>34721</td>
			<td></td>
		</tr>
		<tr>
			<td>XBridge C18, 250x4.6 mm, 5 &#956;M with 4.6x20 mm guard column</td>
			<td>Waters</td>
			<td>186003117, 186003064</td>
			<td></td>
		</tr>
		<tr>
			<td>Agilent 1100 series HPLC system</td>
			<td>Agilent Technologies</td>
			<td>G1380-90000</td>
			<td></td>
		</tr>
		<tr>
			<td>1.7mL centrifuge tube</td>
			<td>Sorenson</td>
			<td>11700</td>
			<td></td>
		</tr>
		<tr>
			<td>Hamilton Glass Syringes, 5mL, 50&#181;L and 250&#181;L</td>
			<td>Hamilton</td>
			<td>81517, 80975, 81175</td>
			<td></td>
		</tr>
		<tr>
			<td>Pasteur Pipettes</td>
			<td>FisherBrand</td>
			<td>13-678-20A</td>
			<td></td>
		</tr>
		<tr>
			<td>Pasteur Pipette Bulbs</td>
			<td>Sigma-Aldrich</td>
			<td>Z111597</td>
			<td></td>
		</tr>
		<tr>
			<td>Bath Sonicator</td>
			<td>Branson 1800 Ultrasonic Cleaner</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum Centrifuge</td>
			<td colspan="2">Labconco Centrivap Acid-Resistant Concentrator System</td>
			<td></td>
		</tr>
		<tr>
			<td>MicroSpin Columns, C18 Silica</td>
			<td>The Nest Group</td>
			<td>SEM SS18V</td>
			<td></td>
		</tr>
	</tbody>
</table>

the mplex protocol for multi-omic analyses of soil samples

Mass spectrometry (MS)-based integrated metaproteomic, metabolomic, and lipidomic (multi-omic) studies are transforming our ability to understand and characterize microbial communities in environmental and biological systems. These measurements are even enabling enhanced analyses of complex soil microbial communities, which are the most complex microbial systems known to date. Multi-omic analyses, however, do have sample preparation challenges, since separate extractions are typically needed for each omic study, thereby greatly amplifying the preparation time and amount of sample required. To address this limitation, a 3-in-1 method for the simultaneous extraction of metabolites, proteins, and lipids (MPLEx) from the same soil sample was created by adapting a solvent-based approach. This MPLEx protocol has proven to be both simple and robust for many sample types, even when utilized for limited quantities of complex soil samples. The MPLEx method also greatly enabled the rapid multi-omic measurements needed to gain a better understanding of the members of each microbial community, while evaluating the changes taking place upon biological and environmental perturbations.

When the MPLEx protocol was used to extract molecules from Kansas native prairie soil (a Mollisol soil), the triplicate analyses provided results for 3376&#160;peptides, 105 lipids, and 102 polar metabolites (all unique identifications). While the MPLEx protocol has been well-established for general extraction of lipids and metabolites12,13,14,15,<sup...

Watch this Scientific Journal Video about The MPLEx Protocol for Multi-omic Analyses of Soil Samples at JoVE.com

The MPLEx Protocol for Multi-omic Analyses of Soil Samples

A protocol is presented for simultaneously extracting metabolites, proteins, and lipids from a single soil sample, allowing reduced sample preparation times and enabling multi-omic mass spectrometry analyses of samples with limited quantities.

Mass spectrometry (MS)-based integrated metaproteomic, metabolomic, and lipidomic (multi-omic) studies are transforming our ability to understand and ...

This method is used in the proteomics, metabolomics, and lipidomics fields by helping obtain comprehensive information about the molecular changes taking place in soil-associated microbial communities due to environmental perturbations. The main advantage of this technique is that obtaining multiple analytes from a single soil sample increases precision and accuracy while decreasing sample preparation time and effort. To begin, for each 20-gram soil sample, weigh 10 grams into two separate 50-milliliter methanol/chloroform-compatible tubes.Use plastic tubes made from PTFE, as chloroform will leach most plastics, contaminating the samples. Add approximately 10 milliliters of chloroform-washed stainless steel and garnet beads to each tube. Then, while on ice, add four milliliters of cold ultrapure water to each tube, and transfer the samples in an ice bucket into a fume hood.Using a 25-milliliter glass serological pipette, quickly add 20 milliliters of ice-cold two to one chloroform to methanol volume/volume to the tubes. Tighten the lids and vortex the soil mixture into solution. The chloroform-methanol helps break down the cell wall of prokaryotes and also inactivates enzymatic activities.Next, attach the tubes to 50-milliliter tube vortex attachments, and horizontally vortex for 10 minutes at four degrees Celsius inside a fridge if possible. Then, place the samples inside a negative 80 degree Celsius freezer for approximately 15 minutes in order to cool them down completely. Then, using a probe sonicator inside a fume hood, sonicate each sample with a six millimeter, 1/4-inch probe at 60%amplitude for 30 seconds on ice.Following sonication, place the samples in a negative 80 degree Celsius freezer, as sonicating can generate a lot of heat. After repeating the horizontal vortexing, sonication, and freezing steps, centrifuge the samples at 4, 000 times gravity and four degrees Celsius for five minutes. At this point, the sample will be separated into the upper metabolite layer, the protein interlayer, and the lower lipid layer.Place the samples on ice. Then, inside a fume hood, use a 10-milliliter glass serological pipette to transfer the upper metabolite layers from the two 50-milliliter tubes into one large glass vial. Now, slightly tilt the 50-milliliter tube to release the protein interlayer so that it is free-floating upon the lower lipid layer.Then, using a clean stainless steel flat-head lab spatula, carefully scoop both of the protein interlayers, and place them together into one new 50-milliliter tube. Using a 25-milliliter glass serological pipette, transfer the lower lipid layers into one large glass vial. Add 20 milliliters of ice-cold methanol to the two tubes with debris and to the one tube with the protein interlayer.Briefly vortex the tubes, and centrifuge the debris pellets and protein interlayer at 4, 000 times gravity and four degrees Celsius for five minutes. Then, decant the methanol into a hazardous waste container inside a fume hood. Freeze the protein and debris pellets in liquid nitrogen, and dry them in a lyophilizer for about two hours.Add 20 milliliters of protein solubilization buffer in 50-millimolar tris buffer, pH 8.0, to each of the debris pellets and 10 milliliters to the protein interlayer tube. In the fume hood, probe sonicate the samples at 20%amplitude for 30 seconds to bring them into solution. Vortex the samples for two minutes.Then, place the protein interlayer sample into a lab tube rotator at 50 degrees Celsius for 30 minutes to solubilize the protein. Horizontally vortex the debris samples for an additional 10 minutes to lyse any remaining intact cells. Then, rotate with the protein interlayer samples for the remaining 20 minutes.Centrifuge all of the samples at 4, 500 times gravity at room temperature for 10 minutes, and collect the supernatant from each tube per sample into two 50-milliliter tubes. Add 10 milliliters of solubilization buffer to the protein interlayer pellet. Then, sonicate and vortex the pellet back into solution.Following centrifugation, equally combine the supernatants into the two 50-milliliter tubes with the debris pellet supernatants, and centrifuge the tubes in a fixed-angle bucket rotor at 8, 000 times gravity and four degrees Celsius for 10 minutes in order to pellet any remaining debris. Divide the supernatants into two 50-milliliter tubes. Then, using a 10-milliliter glass serological pipette, add 7.5 milliliters of TCA to each tube.Vortex the samples into solution. Then, place the samples in a negative 20 degree Celsius freezer for two hours to overnight. To pellet the precipitated protein, centrifuge the sample at 4, 500 times gravity and four degrees Celsius for 10 minutes, and decant the supernatant into waste.Add 10 milliliters of 100%ice-cold acetone to each protein pellet. Vortex the tubes, and combine like pellets into one tube. Centrifuge and then decant the acetone.Using a smaller volume of acetone, wash the pellet twice, and transfer the suspension to a 1.5 or two-milliliter tube for the final spin. Decant the supernatant into waste, and allow the pellet to dry inverted on a paper wipe in a fume hood for approximately 20 minutes. Depending on the size of the pellet, add 100 to 200 microliters of the protein solubilization buffer.Sonicate and vortex the pellet into solution. Note that the sample may be viscous due to humic substances precipitating along with the protein, which will be removed with a subsequent centrifugation. Finally, shake the sample in an incubator or shaker at 300 rpm and 40 degrees Celsius for 30 minutes, to solubilize the protein into solution before proceeding to protein digestion or snap freezing for future processing.Using the MPLEx protocol demonstrated in this video, 3, 376 peptides, 105 lipids, and 102 polar metabolites were extracted from Kansas native prairie soil, and the protocol's extraction of proteins is compared to protein extraction kits and SDS extractions using reverse-phase LC-MS/MS. When initially comparing three replicates of the commercial protein extraction kit and SDS methods, only 12%of the peptides overlapped between the two techniques, showing the complexity of the microbial community and different extraction effects. Upon comparison of MPLEx with a commercial protein extraction kit and SDS extracts, about 38%of the peptides observed using the MPLEx method were also detected when using the SDS and/or commercial kit extractions.Considering the number of species in the Kansas soil bacterial community and its metagenome, the overlap of peptide identifications is reasonable. As shown here, the broad applicability of the MPLEx approach has been previously evaluated using the archaeon S.acidocaldarius, a unicyanobacterial consortium, mouse brain cortex tissue, human urine, and leaves from A.thaliana. In all cases, the number of proteins observed from the MPLEx method was similar to that for the controls, indicating its utility for many different sample types.After watching this video, you should have a good understanding of how to obtain proteins, metabolites, and lipids from a single soil sample. While attempting this procedure, it's important to be flexible, as all soil types are different. For example, the size of the protein interlayer will vary, depending on the soil biomass and humic substances present in the soil.Don't forget that working with chloroform can be extremely hazardous, and precautions such as working in a fume hood should always be taken while attempting this procedure.

the-mplex-protocol-for-multi-omic-analyses-of-soil-samples

Research

JoVE Journal

Chemistry

10.7K vistas.  Pacific Northwest National Laboratory. This method is used in the proteomics, metabolomics, and lipidomics fields by helping obtain comprehensive information about the molecular changes taking place in soil-associated microbial communities due to environmental perturbations. The main advantage of this technique is that obtaining multiple analytes from a single soil sample increases precision and accuracy while decreasing sample preparation time and effort. To begin, for each 20-gram soil sample, weigh 10 grams into two separate 50...