This work was funded by Genome BC, Genome Canada, and Coastal Genomics. The authors thank Kirby Cronin and Michael Chan for their help in sample collection and processing. We also would like to acknowledge Thea Van Rossum and Dr. Fiona Brinkman for bioinformatics assistance.

1. Water Collection and Filtration
<ol>
	<li>Collect freshwater samples from various sites (Figure 1). Pass samples through a series of filters: 1 &#181;m filter, 0.2 &#181;m filter, and 30 kDa cutoff tangential flow filter to systematically separate eukaryotic, bacterial and viral sized particles, respectively. 
	Note: Only the purification and analysis of the material recovered on the 0.2 &#181;m filters (free-living bacteria) is described in this report, but similar approaches can be used for the other particles recovered from the filters.</li>
</ol>
2. Bacterial Concentration, DNA Extraction and Purification
<ol>
	<li>Remove the 0.2 &#181;m membrane filter(s) from the water filtration system (schematic diagram, Figure 2). Fold the 0.2 &#181;m disc filter in half and place it into a 50 ml tube with the open side up. Add 5 ml of 1x phosphate buffered solution (PBS) and 0.01% Tween, pH 7.4 into the tube. If more than one filter is used during the process employ a different tube per filter. Store tube(s) with filter at 4 &#176;C until processed. Otherwise, proceed to step 2.2.</li>
	<li>Remove the 0.2 &#181;m membrane filter from the 50 ml tube with sterile forceps. Place filter(s) on a petri dish (leave the PBS buffer in the tube).
	<ol>
		<li>With sterile forceps and sterile scissors, cut the filter into small strips (1 cm x 1 cm). Disinfect forceps and scissors by soaking in 70% isopropanol, wiping with a DNA surface decontaminant and rinsing with ultrapure water of type 1 between different samples.</li>
	</ol>
	</li>
	<li>Place the filter cut into strips back into the same 50 ml tube. Add 10 ml of 1x PBS and 0.01% Tween, pH 7.4 to the filter so there is a total of 15 ml of buffer in the 50 ml tube.</li>
	<li>Add 6 clean tungsten beads (3 mm diameter) to each 50 ml tube, cover the tube with Parafilm, and vortex vigorously for 20 min (use 50 ml tubes vortex adaptor). If multiple filters are processed from one sample, transfer and pool all the homogenate into a clean 50 ml tube. Centrifuge the tubes at 3,300 x g for 15 min at 4 &#176;C.</li>
	<li>Resuspend the pellet and aliquot bacterial cells (~1 ml aliquots) into 1.7 ml microcentrifuge tubes. Note that there will be 5 microcentrifuge tubes per sample.</li>
	<li>Spin down the microcentrifuge tubes at 10,000 x g for 10 min, and remove most of the supernatant down to ~200 &#181;l mark.</li>
	<li>Store the samples at -80 &#176;C, or proceed to extract bacterial DNA by using a commercially available DNA isolation kit as per the manufacturer&#8217;s instructions. During bacterial DNA extraction use either PBS or water as a negative extraction control, and E. coli as a positive extraction control.</li>
	<li>Because DNA from multiple tubes are being extracted, pool parallel sub-aliquots from the same sample into one 2 ml tube. Then conduct an O/N&#160;precipitation by using a solution comprised of 0.1 volumes of 3 M sodium acetate, 2 volumes of 100% ethanol, and 5 &#181;l of 5 &#181;g/&#181;l linear acrylamide. Mix well and store samples at -80 &#176;C.</li>
	<li>Centrifuge at maximum speed (17,000 x g) for 30 min at 4 &#176;C. Wash pellet with 1 ml of ice-cold 70% ethanol, air dry in a biosafety cabinet for no more than 5 min and resuspend DNA pellet in 34 &#181;l of 10 mM Tris-Cl, pH 8.5. 
	Note: Linear acrylamide will help to visualize DNA pellet after the O/N precipitation.</li>
	<li>Determine DNA quantity and quality using a high sensitivity fluorescent nucleic acid quantitation assay and a microvolume spectrophotometer, respectively, following the manufacturers&#8217; instructions (See Table of Materials). 
	Note: If multiple samples are prepared at the time, an ultrasensitive fluorescent nucleic acid assay for quantifying dsDNA and plate-based fluorometer/spectrophotometer can be used instead.</li>
</ol>
3. DNA Library Preparation
<ol>
	<li>Normalize genomic bacterial DNA extracted from water samples to a concentration of ~0.2 ng/&#956;l.</li>
	<li>Enzymatically fragment one nanogram of bacterial DNA using a transposon-based method (tagmentation). Add adapter and index sequences onto fragmented DNA following the manufacturer&#8217;s instructions. Subject tagmented samples to 12 cycles of PCR as indicated in the manufacturer&#8217;s instructions, at which point the sequencing indexes are incorporated.</li>
</ol>
4. Automated Gel Size Selection
<ol>
	<li>Skip standard post-PCR clean-up step described in the manufacturer&#8217;s instructions (See Table of Materials). Size select post-PCR samples directly using an automated gel-based size selection platform.
	<ol>
		<li>Add 3.5 &#956;l of loading buffer to each sample.</li>
		<li>Following the manufacturer&#39;s protocol, load the samples onto the electrophoresis workstation, specifying a size-selection target of 500-800 bp, in a 300 &#956;l extraction volume, using a pre-cast 1.5% agarose cassette.</li>
		<li>Concentrate the raw output material (300 &#956;l) down to 25 &#956;l via ethanol precipitation. 
		Note: Alternatively, use the electrophoresis workstation to automate concentration for larger numbers of samples via filter plate and vacuum manifold.
		<ol>
			<li>Precipitate the raw elution volume using 0.1 volumes of 3 M sodium acetate, 2 volumes of 100% ethanol and 5 &#956;l of 5 &#181;g/&#181;l linear acrylamide. Mix well, place samples at -80 &#176;C O/N. Centrifuge samples at 17,000 x g for 30 min.</li>
			<li>Discard supernatants and proceed to wash DNA pellet with 1 ml of ice-cold 70% ethanol.</li>
			<li>Centrifuge samples again at 17,000 x g for 30 min, discard supernatants, air dry, and finally resuspend DNA pellet in 25 &#956;l of 10 mM Tris-Cl, pH 8.5.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>(Optional) Use 1 &#956;l of DNA libraries size selected with the automated gel size selection platform to make a five-fold dilution using Tris-EDTA buffer solution, pH 8.0. Analyze libraries using a chip-based capillary electrophoresis instrument to analyze dsDNA quality according to manufacturer&#8217;s instructions.</li>
</ol>
5. Library Normalization and Sequencing
<ol>
	<li>Proceed to normalize samples using library normalization beads (included in the transposon-based library preparation kit) as described in the manufacturer&#8217;s preparation guide.
	<ol>
		<li>Alternatively, measure dsDNA libraries using a high sensitivity fluorescent nucleic acid quantitation assay, followed by pooling at equimolar ratios to reach a final dsDNA concentration of 2 nM. Proceed to denature libraries using 10 &#956;l of pooled libraries and 10 &#956;l of 0.2 N NaOH, incubate for 5 min at RT. Dilute denatured libraries using hybridization buffer (included with the transposon-based preparation kit) to a final volume of 1 ml and concentration of 11.5 pM.</li>
	</ol>
	</li>
	<li>Load samples in a next-generation sequencing platform by following the manufacturer&#8217;s standard sequencing protocols.</li>
</ol>

<ol>
	<li>Siuda, W., Chrost, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concentration+and+susceptibility+of+dissolved+DNA+for+enzyme+degradation+in+lake+water+-+some+methodological+remarks.">Concentration and susceptibility of dissolved DNA for enzyme degradation in lake water - some methodological remarks.</a> Aquatic Microbial Ecology. 21, 195-201 (2000).</li><li>Ficetola, G. F., Miaud, C., Pompanon, F., Taberlet, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Species+detection+using+environmental+DNA+from+water+samples.">Species detection using environmental DNA from water samples.</a> Biology letters. 4, 423-425 (2008).</li><li>Liles, M. 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=Recovery,+purification,+and+cloning+of+high-molecular-weight+DNA+from+soil+microorganisms.">Recovery, purification, and cloning of high-molecular-weight DNA from soil microorganisms.</a> Applied and environmental microbiology. 74, 3302-3305 (2008).</li><li>Bey, B. S., Fichot, E. B., Dayama, G., Decho, A. W., Norman, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+of+high+molecular+weight+DNA+from+microbial+mats.">Extraction of high molecular weight DNA from microbial mats.</a> BioTechniques. 49, 631-640 (2010).</li><li>Tebbe, C. C., Vahjen, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interference+of+humic+acids+and+DNA+extracted+directly+from+soil+in+detection+and+transformation+of+recombinant+DNA+from+bacteria+and+a+yeast.">Interference of humic acids and DNA extracted directly from soil in detection and transformation of recombinant DNA from bacteria and a yeast.</a> Applied and environmental microbiology. 59, 2657-2665 (1993).</li><li>Solonenko, S. 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=Sequencing+platform+and+library+preparation+choices+impact+viral+metagenomes.">Sequencing platform and library preparation choices impact viral metagenomes.</a> BMC genomics. 14, 320 (2013).</li><li>Aird, D., 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=Analyzing+and+minimizing+PCR+amplification+bias+in+Illumina+sequencing+libraries.">Analyzing and minimizing PCR amplification bias in Illumina sequencing libraries.</a> Genome biology. 12, R18 (2011).</li><li>Quail, M. A., Swerdlow, H., Turner, D. 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=Improved+protocols+for+the+illumina+genome+analyzer+sequencing+system.">Improved protocols for the illumina genome analyzer sequencing system.</a> Current protocols in human genetics / editorial board, Jonathan L. Haines .. [et al.]. 18, 18 (2009).</li><li>Head, S. 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=Library+construction+for+next-generation+sequencing:+overviews+and+challenges.">Library construction for next-generation sequencing: overviews and challenges.</a> BioTechniques. 56, 61-64, 66, 68 (2014).</li><li>Dijk, E. L., Jaszczyszyn, Y., Thermes, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Library+preparation+methods+for+next-generation+sequencing:+tone+down+the+bias.">Library preparation methods for next-generation sequencing: tone down the bias.</a> Experimental cell research. 322, 12-20 (2014).</li><li>Grunenwald, H., Baas, B., Caruccio, N., Syed, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid,+high-throughput+library+preparation+for+next-generation+sequencing.">Rapid, high-throughput library preparation for next-generation sequencing.</a> Nature Methods. 7, (2010).</li><li>Sambrook, J., Russell, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular cloning : a laboratory manual. , (2001).</li><li>Lee, P. Y., Costumbrado, J., Hsu, C. Y., Kim, Y. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Agarose+gel+electrophoresis+for+the+separation+of+DNA+fragments.">Agarose gel electrophoresis for the separation of DNA fragments.</a> Journal of visualized experiments. , (2012).</li><li>Quail, M. 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=A+large+genome+center's+improvements+to+the+Illumina+sequencing+system.">A large genome center's improvements to the Illumina sequencing system.</a> Nature methods. 5, 1005-1010 (2008).</li><li>Marine, 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=Evaluation+of+a+transposase+protocol+for+rapid+generation+of+shotgun+high-throughput+sequencing+libraries+from+nanogram+quantities+of+DNA.">Evaluation of a transposase protocol for rapid generation of shotgun high-throughput sequencing libraries from nanogram quantities of DNA.</a> Applied and environmental microbiology. 77, 8071-8079 (2011).</li><li>Rohland, N., Reich, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cost-effective+high-throughput+DNA+sequencing+libraries+for+multiplexed+target+capture.">Cost-effective high-throughput DNA sequencing libraries for multiplexed target capture.</a> Genome research. 22, 939-946 (2012).</li><li>Lamble, S., 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=Improved+workflows+for+high+throughput+library+preparation+using+the+transposome-based+nextera+system.">Improved workflows for high throughput library preparation using the transposome-based nextera system.</a> Bmc Biotechnology. 13, (2013).</li><li>Picelli, S., 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=Tn5+transposase+and+tagmentation+procedures+for+massively+scaled+sequencing+projects.">Tn5 transposase and tagmentation procedures for massively scaled sequencing projects.</a> Genome research. , (2014).</li><li>Rhodes, J., Beale, M. A., Fisher, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Illuminating+Choices+for+Library+Prep:+A+Comparison+of+Library+Preparation+Methods+for+Whole+Genome+Sequencing+of+Cryptococcus+neoformans+Using+Illumina+HiSeq.">Illuminating Choices for Library Prep: A Comparison of Library Preparation Methods for Whole Genome Sequencing of Cryptococcus neoformans Using Illumina HiSeq.</a> PloS One. 9, e113501 (2014).</li></ol>

Jared R. Slobodan and Matthew J. Nesbitt both hold shares of Coastal Genomics, a privately owned British Columbia corporation offering the Ranger Technology.

The presence of adapter dimers and clustering of small insert sizes preferentially being sequenced in current platforms represent a decrease in useable yields and under-utilization of the equipment&#8217;s capacity15. The use of bead beating methods combined with a transposon-based approach to prepare libraries may result in more DNA shearing compared to other methods of extraction4,5. Nevertheless, all methods of extraction and library preparation potentially introduce biases to the distribution of...

Metagenomics involves the sequencing of all the genetic material in a sample to characterize the microbial communities present. It is a complex and expensive process which involves the conversion of extracted nucleic acids into DNA libraries followed by next-generation sequencing. High quality libraries are essential for maximal data output and accurate metagenomics analysis. Environmental samples, such as water samples, often pose significant challenges to generating high quality libraries, due to low amounts of DNA that may also be degraded1-3 and the presence of inhibitors of PCR4-6. 
High quality libraries ideally consist of longer segments of DNA within a narrow range of lengths. In order to maximize the amount of useful data generated per sequencing run, the length of the DNA in the library should be at least as long as the maximum read length of the sequencing method being used. When using a sequencing-by-synthesis technology such as the Illumina MiSeq, the size of the DNA fragments affects the efficiency at which clusters are generated on the flow cell. For instance, when a library contains both shorter and longer DNA fragments, the shorter ones will be over-represented in the sequencing data7,8. In contrast, a library with similarly sized DNA fragments will be proportionally represented in the sequencing data. Many library preparation kits use ligation-based methods to add adapters to the DNA fragments and size selection is necessary to remove adapter dimers that do not contain an insert9,10. There are numerous methods11,12 to achieve this but the one technique that gives the most consistent results is the electrophoretic separation of DNA followed by the recovery of the desired lengths of DNA13,14. This process can be performed manually for a small number of samples, but when faced with processing hundreds of samples, automated solutions are required. The currently available platforms for automated gel size selection are low throughput and new platforms are needed to process large numbers of samples for sequencing. The Ranger Technology can be integrated with existing liquid handling workstations to enable the use of agarose gel electrophoresis for size selection and analytical purposes on a scale that satisfies today&#8217;s high throughput environment.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Peristaltic pump Masterflex P/S 1400 Series</td>
			<td>Thermo Scientific&#160;</td>
			<td>1400-1620</td>
			<td></td>
		</tr>
		<tr>
			<td>0.2 &#181;m Supor Membrane</td>
			<td>VWR</td>
			<td>CA28143-969</td>
			<td>Pall Corporation, Ann Harbor, MI</td>
		</tr>
		<tr>
			<td>Tungsten carbide beads 3 mm (200)</td>
			<td>Qiagen</td>
			<td>69997</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropyl alcohol 70%</td>
			<td>Jedmon Products</td>
			<td>825751</td>
			<td>Healthcare Plus</td>
		</tr>
		<tr>
			<td>DNA away</td>
			<td>VWR</td>
			<td>7010</td>
			<td>Molecular BioProducts, Inc. San Diego, CA</td>
		</tr>
		<tr>
			<td>Milli-Q water purification system</td>
			<td>Fisher Scientific</td>
			<td>ZMQS6VF0Y</td>
			<td>Merck Millipore. This system has been discontinued.</td>
		</tr>
		<tr>
			<td>20 X PBS pH 7.5</td>
			<td>VWR</td>
			<td>E703-1L</td>
			<td>Amresco, Inc., Solon, OH</td>
		</tr>
		<tr>
			<td>Tween 20</td>
			<td>Fisher Scientific</td>
			<td>BP337-100</td>
			<td>Fisher chemicals</td>
		</tr>
		<tr>
			<td>Vortex adapter for 2 (50 ml) tubes</td>
			<td>VWR</td>
			<td>13000-V1-50</td>
			<td>MoBio, Carlsbad, CA</td>
		</tr>
		<tr>
			<td>Vortex-Genie 2, 120V (Model G560)</td>
			<td>VWR</td>
			<td>SI-0236</td>
			<td>Scientific Industries, Inc.</td>
		</tr>
		<tr>
			<td>Beckman Centrifuge</td>
			<td>Raeyco Lab Equipment Systems Management Ltd</td>
			<td>Model J-6B</td>
			<td></td>
		</tr>
		<tr>
			<td>PowerLyzer Powersoil DNA isolation kit</td>
			<td>VWR</td>
			<td>12855-100</td>
			<td>MoBio, Carlsbad, CA</td>
		</tr>
		<tr>
			<td>Vortex adapter for 24 (1.5-2 ml) tubes</td>
			<td>VWR</td>
			<td>13000-V1-24</td>
			<td>MoBio, Carlsbad, CA</td>
		</tr>
		<tr>
			<td>Microfuge 18 centrifuge</td>
			<td>Beckman Coulter</td>
			<td>367160</td>
			<td></td>
		</tr>
		<tr>
			<td>Nimbus Select workstation with Ranger Technology</td>
			<td>Hamilton Robotics</td>
			<td>92720-01</td>
			<td>Includes the liquid handling workstation and integrated Ranger Tech (electrophoresis hardware)</td>
		</tr>
		<tr>
			<td>Ranger reagent kit</td>
			<td>Coastal Genomics</td>
			<td>CG-10600-150-12-21</td>
			<td>Includes loading buffer and cassettes</td>
		</tr>
		<tr>
			<td>Ethyl alcohol (anhydrous)</td>
			<td>Commercial Alcohols</td>
			<td>P016EAAN</td>
			<td>Greenfield Ethanol</td>
		</tr>
		<tr>
			<td>Sodium acetate</td>
			<td>Sigma-Aldrich</td>
			<td>S2889-250G</td>
			<td></td>
		</tr>
		<tr>
			<td>Linear acrylamide (5 mg/ml)</td>
			<td>Life Technologies</td>
			<td>AM9520</td>
			<td>Ambion</td>
		</tr>
		<tr>
			<td>Eppendorf refrigerated centrifuge</td>
			<td>Raeyco Lab Equipment Systems Management Ltd.</td>
			<td>5417R</td>
			<td></td>
		</tr>
		<tr>
			<td>Buffer EB (250 ml)</td>
			<td>Qiagen</td>
			<td>19086</td>
			<td></td>
		</tr>
		<tr>
			<td>NanoDrop 1000 Spectrophotometer</td>
			<td>Thermo Scientific</td>
			<td>ND-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Qubit fluorometer</td>
			<td>Life Technologies</td>
			<td>Q32857</td>
			<td>Invitrogen. This product has been discontinued.</td>
		</tr>
		<tr>
			<td>Qubit dsDNA HS assay kit</td>
			<td>Life Technologies</td>
			<td>Q32854</td>
			<td>Invitrogen</td>
		</tr>
		<tr>
			<td>High sensitivity DNA reagent</td>
			<td>Agilent Technologies</td>
			<td>5067-4626</td>
			<td></td>
		</tr>
		<tr>
			<td>High sensitivity DNA chips</td>
			<td>Agilent Technologies</td>
			<td>5067-4626</td>
			<td></td>
		</tr>
		<tr>
			<td>Agilent 2011 Bioanalyzer</td>
			<td>Agilent Technologies</td>
			<td>G2938B</td>
			<td></td>
		</tr>
		<tr>
			<td>Nextera XT DNA sample preparation kit</td>
			<td>Illumina</td>
			<td>FC-131-1024</td>
			<td></td>
		</tr>
		<tr>
			<td>Nextera XT index kit</td>
			<td>Illumina</td>
			<td>FC-131-1001</td>
			<td></td>
		</tr>
		<tr>
			<td>MiSeq reagent kit v2 (500-cycles)</td>
			<td>Illumina</td>
			<td>MS-102-2003</td>
			<td></td>
		</tr>
		<tr>
			<td>Miseq system</td>
			<td>Illumina</td>
			<td>SY-410-1003</td>
			<td></td>
		</tr>
	</tbody>
</table>

automated gel size selection to improve the quality of next-generation sequencing libraries prepared from environmental water samples

Next-generation sequencing of environmental samples can be challenging because of the variable DNA quantity and quality in these samples. High quality DNA libraries are needed for optimal results from next-generation sequencing. Environmental samples such as water may have low quality and quantities of DNA as well as contaminants that co-precipitate with DNA. The mechanical and enzymatic processes involved in extraction and library preparation may further damage the DNA. Gel size selection enables purification and recovery of DNA fragments of a defined size for sequencing applications. Nevertheless, this task is one of the most time-consuming steps in the DNA library preparation workflow. The protocol described here enables complete automation of agarose gel loading, electrophoretic analysis, and recovery of targeted DNA fragments. 
In this study, we describe a high-throughput approach to prepare high quality DNA libraries from freshwater samples that can be applied also to other environmental samples. We used an indirect approach to concentrate bacterial cells from environmental freshwater samples; DNA was extracted using a commercially available DNA extraction kit, and DNA libraries were prepared using a commercial transposon-based protocol. DNA fragments of 500 to 800 bp were gel size selected using Ranger Technology, an automated electrophoresis workstation. Sequencing of the size-selected DNA libraries demonstrated significant improvements to read length and quality of the sequencing reads.

DNA Concentration, and Quality Assessment
Bacterial DNA concentrations ranged from 0.01 to 0.11 ng/ml per water sample of the different watershed sites (Table 1). DNA isolated from bacterial fraction had A260/280 and A260/230 ratios of 1.4 to 1.8 and 0.3 to 1.6, respectively. While some of the A260/230 ratios were relatively low, no apparent inhibition was observed in the prepared library and other downstream applications. Thes...

Watch this Scientific Journal Video about Automated Gel Size Selection to Improve the Quality of Next-generation Sequencing Libraries Prepared from Environmental Water Samples at JoVE.com

Automated Gel Size Selection to Improve the Quality of Next-generation Sequencing Libraries Prepared from Environmental Water Samples

This manuscript describes an automated gel size selection approach for purifying DNA fragments for next-generation sequencing. The Ranger Technology provides complete automation of the entire process of agarose gel loading, electrophoretic analysis, and recovery of targeted DNA fragments allowing for high-throughput and high quality next-generation sequencing libraries.

Next-generation sequencing of environmental samples can be challenging because of the variable DNA quantity and quality in these samples. High quality DNA ...

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10.5K vistas.  The University of British Columbia. This manuscript describes an automated gel size selection approach for purifying DNA fragments for next-generation sequencing. The Ranger Technology provides complete automation of the entire process of agarose gel loading, electrophoretic analysis, and recovery of targeted DNA fragments allowing for high-throughput and high quality next-generation sequencing libraries. 

Video: Automated Gel Size Selection to Improve the Quality of Next-generation Sequencing Libraries Prepared from Environmental Water Samples

EPA Method 1615. Measurement of Enterovirus and Norovirus Occurrence in Water by Culture and RT-qPCR. I. Collection of Virus Samples

EPA Method 1615 was developed with a goal of providing a standard method for measuring enteroviruses and noroviruses in environmental and drinking waters. The standardized sampling component of the method concentrates viruses that may be present in water by passage of a minimum specified volume of water through an electropositive cartridge filter. The minimum specified volumes for surface and finished/ground water are 300 L and 1,500 L, respectively. A major method limitation is the tendency for the filters to clog before meeting the sample volume requirement. Studies using two different, but equivalent, cartridge filter options showed that filter clogging was a problem with 10% of the samples with one of the filter types compared to 6% with the other filter type. Clogging tends to increase with turbidity, but cannot be predicted based on turbidity measurements only. From a cost standpoint one of the filter options is preferable over the other, but the water quality and experience with the water system to be sampled should be taken into consideration in making filter selections.

EPA Method 1615 uses an electropositive filter to concentrate enteroviruses and noroviruses in environmental and drinking waters. This manuscript describes the procedure for collecting samples for Method 1615 analyses.

EPA Method 1615 was developed with a goal of providing a standard method for measuring enteroviruses and noroviruses in environmental and drinking waters. ...

Physical Isolation of Endospores from Environmental Samples by Targeted Lysis of Vegetative Cells

Endospore formation is a survival strategy found among some bacteria from the phylum Firmicutes. During endospore formation, these bacteria enter a morpho-physiological resting state that enhances survival under adverse environmental conditions. Even though endospore-forming Firmicutes are one of the most frequently enriched and isolated bacterial groups in culturing studies, they are often absent from diversity studies based on molecular methods. The resistance of the spore core is considered one of the factors limiting the recovery of DNA from endospores. We developed a method that takes advantage of the higher resistance of endospores to separate them from other cells in a complex microbial community using physical, enzymatic and chemical lysis methods. The endospore-only preparation thus obtained can be used for re-culturing or to perform downstream analysis such as tailored DNA extraction optimized for endospores and subsequent DNA sequencing. This method, applied to sediment samples, has allowed the enrichment of endospores and after sequencing, has revealed a large diversity of endospore-formers in freshwater lake sediments. We expect that the application of this method to other samples will yield a similar outcome.

A method to single out bacterial endospores from complex microbial communities was developed to perform tailored culture or molecular studies of this group of bacteria.

Endospore formation is a survival strategy found among some bacteria from the phylum Firmicutes. During endospore formation, these bacteria enter a ...

A Simple Method for Automated Solid Phase Extraction of Water Samples for Immunological Analysis of Small Pollutants

A new method for solid phase extraction (SPE) of environmental water samples is proposed. The developed prototype is cost-efficient and user friendly, and enables to perform rapid, automated and simple SPE. The pre-concentrated solution is compatible with analysis by immunoassay, with a low organic solvent content. A method is described for the extraction and pre-concentration of natural hormone 17&#946;-estradiol in 100 ml water samples. Reverse phase SPE is performed with octadecyl-silica sorbent and elution is done with 200 &#181;l of methanol 50% v/v. Eluent is diluted by adding di-water to lower the amount of methanol. After preparing manually the SPE column, the overall procedure is performed automatically within 1 hr. At the end of the process, estradiol concentration is measured by using a commercial enzyme-linked immune-sorbent assay (ELISA). 100-fold pre-concentration is achieved and the methanol content in only 10% v/v. Full recoveries of the molecule are achieved with 1 ng/L spiked de-ionized and synthetic sea water samples.

A protocol for the extraction and pre-concentration of estradiol from water samples by using an automated and miniaturized system is presented.

A new method for solid phase extraction (SPE) of environmental water samples is proposed. The developed prototype is cost-efficient and user friendly, and ...

Use of a Filter Cartridge for Filtration of Water Samples and Extraction of Environmental DNA

Recent studies demonstrated the use of environmental DNA (eDNA) from fishes to be appropriate as a non-invasive monitoring tool. Most of these studies employed disk fiber filters to collect eDNA from water samples, although a number of microbial studies in aquatic environments have employed filter cartridges, because the cartridge has the advantage of accommodating large water volumes and of overall ease of use. Here we provide a protocol for filtration of water samples using the filter cartridge and extraction of eDNA from the filter without having to cut open the housing. The main portions of this protocol consists of 1) filtration of water samples (water volumes &#8804;4 L or &gt;4 L); (2) extraction of DNA on the filter using a roller shaker placed in a preheated incubator; and (3) purification of DNA using a commercial kit. With the use of this and previously-used protocols, we perform metabarcoding analysis of eDNA taken from a huge aquarium tank (7,500 m3) with known species composition, and show the number of detected species per library from the two protocols as the representative results. This protocol has been developed for metabarcoding eDNA from fishes, but is also applicable to eDNA from other organisms.

We describe a protocol for filtration of water samples with a filter cartridge and extraction of environmental DNA (eDNA) without having to cut open the housing to remove the filter. This protocol is developed for metabarcoding eDNA from fishes, but is also applicable to eDNA from other organisms.

Recent studies demonstrated the use of environmental DNA (eDNA) from fishes to be appropriate as a non-invasive monitoring tool. Most of these studies ...

Controlled-release of Chlorine Dioxide in a Perforated Packaging System to Extend the Storage Life and Improve the Safety of Grape Tomatoes

A controlled-release chlorine dioxide (ClO2) pouch was developed by sealing a slurry form of ClO2 into semipermeable polymer film; the release properties of the pouch were monitored in containers with or without fruit. The pouch was affixed to the inside of a perforated clamshell containing grape tomatoes, and the effect on microbial population, firmness, and weight loss was evaluated during a 14 day storage period at 20 &#176;C. Within 3 days, the ClO2 concentration in the clamshells reached 3.5 ppm and remained constant until day 10. Thereafter, it decreased to 2 ppm by day 14. The ClO2 pouch exhibited strong antimicrobial activity, reducing Escherichia coli populations by 3.08 log CFU/g and Alternaria alternata populations by 2.85 log CFU/g after 14 days of storage. The ClO2 treatment also reduced softening and weight loss and extended the overall shelf life of the tomatoes. Our results suggest that ClO2 treatment is useful for extending the shelf life and improving the microbial safety of tomatoes during storage without impairing their quality.

Here, we describe a protocol for the application of a novel, slow-release ClO2 product that reduces spoilage and extends the shelf life of fresh fruit. The slow-release ClO2 product was added to standard commercial grape tomato packaging and tested against Escherichia coli and Alternaria alternata.

A controlled-release chlorine dioxide (ClO2) pouch was developed by sealing a slurry form of ClO2 into semipermeable polymer film; the release properties ...

Extraction of Organochlorine Pesticides from Plastic Pellets and Plastic Type Analysis

Plastic resin pellets, categorized as microplastics (&#8804;5 mm in diameter), are small granules that can be unintentionally released to the environment during manufacturing and transport. Because of their environmental persistence, they are widely distributed in the oceans and on beaches all over the world. They can act as a vector of potentially toxic organic compounds (e.g., polychlorinated biphenyls) and might consequently negatively affect marine organisms. Their possible impacts along the food chain are not yet well understood. In order to assess the hazards associated with the occurrence of plastic pellets in the marine environment, it is necessary to develop methodologies that allow for rapid determination of associated organic contaminant levels. The present protocol describes the different steps required for sampling resin pellets, analyzing adsorbed organochlorine pesticides (OCPs) and identifying the plastic type. The focus is on the extraction of OCPs from plastic pellets by means of a pressurized fluid extractor (PFE) and on the polymer chemical analysis applying Fourier Transform-InfraRed (FT-IR) spectroscopy. The developed methodology focuses on 11 OCPs and related compounds, including dichlorodiphenyltrichloroethane (DDT) and its two main metabolites, lindane and two production isomers, as well as the two biologically active isomers of technical endosulfan. This protocol constitutes a simple and rapid alternative to existing methodology for evaluating the concentration of organic contaminants adsorbed on plastic pieces.

Microplastics act as vector of potentially toxic organic contaminants with unpredictable effects. This protocol describes an alternative methodology for assessing the levels of organochlorine pesticides adsorbed on plastic pellets and identifying the polymer chemical structure. The focus is on pressurized fluid extraction and attenuated total reflectance Fourier transform infrared spectroscopy.

Plastic resin pellets, categorized as microplastics (&#8804;5 mm in diameter), are small granules that can be unintentionally released to the environment ...

Experimental Column Setup for Studying Anaerobic Biogeochemical Interactions Between Iron (Oxy)Hydroxides, Trace Elements, and Bacteria

Fate and speciation of trace elements (TEs), such as arsenic (As) and mercury (Hg), in aquifers are closely related to physio-chemical conditions, such as redox potential (Eh) and pH, but also to microbial activities that can play a direct or indirect role on speciation and/or mobility. Indeed, some bacteria can directly oxidize As(III) to As(V) or reduce As(V) to As(III). Likewise, bacteria are strongly involved in Hg cycling, either through its methylation, forming the neurotoxin monomethyl mercury, or through its reduction to elemental Hg&#176;. The fates of both As and Hg are also strongly linked to soil or aquifer composition; indeed, As and Hg can bind to organic compounds or (oxy)hydroxides, which will influence their mobility. In turn, bacterial activities such as iron (oxy)hydroxide reduction or organic matter mineralization can indirectly influence As and Hg sequestration. The presence of sulfate/sulfide can also strongly impact these particular elements through the formation of complexes such as thio-arsenates with As or metacinnabar with Hg.
Consequently, many important questions have been raised on the fate and speciation of As and Hg in the environment and how to limit their toxicity. However, due to their reactivity towards aquifer components, it is difficult to clearly dissociate the biogeochemical processes that occur and their different impacts on the fate of these TE.
To do so, we developed an original, experimental, column setup that mimics an aquifer with As- or Hg-iron-oxide rich areas versus iron depleted areas, enabling a better understanding of TE biogeochemistry in anoxic conditions. The following protocol gives step by step instructions for the column set-up either for As or Hg, as well as an example with As under iron and sulfate reducing conditions.

Experimental Column Setup for Studying Anaerobic Biogeochemical Interactions Between Iron OxyHydroxides, Trace Elements, and Bacteria

Fate and speciation of arsenic and mercury in aquifers are closely related to physio-chemical conditions and microbial activity. Here, we present an original experimental column setup that mimics an aquifer and enables a better understanding of trace element biogeochemistry in anoxic conditions. Two examples are presented, combining geochemical and microbiological approaches.

Fate and speciation of trace elements (TEs), such as arsenic (As) and mercury (Hg), in aquifers are closely related to physio-chemical conditions, such as ...

Continuous Hydrologic and Water Quality Monitoring of Vernal Ponds

Vernal ponds, also referred to as vernal pools, provide critical ecosystem services and habitat for a variety of threatened and endangered species. However, they are vulnerable parts of the landscapes that are often poorly understood and understudied. Land use and management practices, as well as climate change are thought to be a contribution to the global amphibian decline. However, more research is needed to understand the extent of these impacts. Here, we present methodology for characterizing a vernal pond's morphology and detail a monitoring station that can be used to collect water quantity and quality data over the duration of a vernal pond's hydroperiod. We provide methodology for how to conduct field surveys to characterize the morphology and develop stage-storage curves for a vernal pond. Additionally, we provide methodology for monitoring the water level, temperature, pH, oxidation-reduction potential, dissolved oxygen, and electrical conductivity of water in a vernal pond, as well as monitoring rainfall data. This information can be used to better quantify the ecosystem services that vernal ponds provide and the impacts of anthropogenic activities on their ability to provide these services.

Understanding the ecosystem services and processes provided by vernal ponds and the impacts of anthropogenic activities on their ability to provide these services requires intensive hydrologic monitoring. This sampling protocol using in-situ monitoring equipment was developed to understand the impact of anthropogenic activities on water levels and quality.

Vernal ponds, also referred to as vernal pools, provide critical ecosystem services and habitat for a variety of threatened and endangered species. ...

Optimized Procedure for Determining the Adsorption of Phosphonates onto Granular Ferric Hydroxide using a Miniaturized Phosphorus Determination Method

This paper introduces a procedure to investigate the adsorption of phosphonates onto iron-containing filter materials, particularly granular ferric hydroxide (GFH), with little effort and high reliability. The phosphonate, e.g., nitrilotrimethylphosphonic acid (NTMP), is brought into contact with the GFH in a rotator in a solution buffered by an organic acid (e.g., acetic acid) or Good buffer (e.g., 2-(N-morpholino)ethanesulfonic acid) [MES] and N-cyclohexyl-2-hydroxyl-3-aminopropanesulfonic acid [CAPSO]) in a concentration of 10 mM for a specific time in 50 mL centrifuge tubes. Subsequently, after membrane filtration (0.45 &#181;m pore size), the total phosphorus (total P) concentration is measured using a specifically developed determination method (ISOmini). This method is a modification and simplification of the ISO 6878 method: a 4 mL sample is mixed with H2SO4 and K2S2O8 in a screw cap vial, heated to 148-150 &#176;C for 1 h and then mixed with NaOH, ascorbic acid and acidified molybdate with antimony(III) (final volume of 10 mL) to produce a blue complex. The color intensity, which is linearly proportional to the phosphorus concentration, is measured spectrophotometrically (880 nm). It is demonstrated that the buffer concentration used has no significant effect on the adsorption of phosphonate between pH 4 and 12. The buffers, therefore, do not compete with the phosphonate for adsorption sites. Furthermore, the relatively high concentration of the buffer requires a higher dosage concentration of oxidizing agent (K2S2O8) for digestion than that specified in ISO 6878, which, together with the NaOH dosage, is matched to each buffer. Despite the simplification, the ISOmini method does not lose any of its accuracy compared to the standardized method.

This paper introduces a procedure to investigate the adsorption of phosphonates onto iron-containing filter materials, particularly granular ferric hydroxide, with little effort and high reliability. In a buffered solution, the phosphonate is brought into contact with the adsorbent using a rotator and then analyzed via a miniaturized phosphorus determination method.

This paper introduces a procedure to investigate the adsorption of phosphonates onto iron-containing filter materials, particularly granular ferric ...

Composition and Distribution Analysis of Bioaerosols Under Different Environmental Conditions

Variable microorganisms in particulate matter (PM) under different environmental conditions may have significant impacts on human health. In this study, we described a protocol for multiple analyses of the biological compositions in environmental PM. Five experiments are presented: (1) PM number monitoring by using a laser particle counter; (2) PM collection by using a cyclonic aerosol sampler; (3) PM collection by using a high-volume air sampler with filters; (4) culturable microbes collection by the Andersen six-stage sampler; and (5) detection of biological composition of environmental PM by bacterial 16SrDNA and fungal ITS region sequencing. We selected hazy days and a livestock farm as two typical examples of the application in this protocol. In this study, these two sampling methods, cyclonic aerosol sampler and filter sampler, showed different sampling efficiency. The cyclonic aerosol sampler performed much better in terms of collecting bacteria, while these two methods showed the same efficiency in collecting fungi. Filter samplers can work under low temperature conditions while cyclonic aerosol samplers have a sampling limitation for temperature. A solid impacting sampler, such as an Andersen six-stage sampler, can be used to sample bioaerosols directly into the culture medium, which increases the survival rate of culturable microorganisms. However, this method mainly relies on culture while more than 99% of microbes cannot be cultured. DNA extracted from the culturable bacteria collected by the Andersen six-stage sampler and samples collected by cyclonic aerosol sampler and filter sampler were detected by bacterial 16S rDNA and fungal ITS region sequencing.All the methods above may have wide application in many fields of study, such as environmental monitoring and airborne pathogen detection. From these results, we can conclude that these methods can be used under different conditions and may help other researchers further explore the health impacts of environmental bioaerosols.

Understanding the biological composition of environmental particulate matter is important for the study of its significant impacts on human health and disease spread. Here, we used three types of bioaerosol sampling methods and a biological analysis of airborne microbes to better explore airborne microbial communities under different environmental conditions.

Variable microorganisms in particulate matter (PM) under different environmental conditions may have significant impacts on human health. In this study, ...