This work was funded by the National Science Foundation Environmental Genomics Program (Grant No. EF-0723707).

1. Microbial Cell Extraction:
<ol>
<li>Homogenize microbial mats with a sterile grinding pestle by mixing thoroughly. Place approximately all 30 g (wet weight) of homogenized mat material into sterile container of Waring blender, add about 100 mL of 1 M NaCl (or a concentration specific to sample in use), and blend three times at medium speed for 1 min with intermittent cooling in a -20&deg;C freezer for 1 min. Transfer the slurry into a 250 mL centrifuge bottle and fill the remaining empty volume with 1 M NaCl. Prepar...

<ol>
	<li>Decho, A. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microbial+biofilms+in+intertidal+systems:+an+overview.">Microbial biofilms in intertidal systems: an overview.</a> Cont. Shelf Res. 20, 1257-1273 (2000).</li><li>Dupraz, C., Visscher, P. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microbial+lithification+in+marine+stromatolites+and+hypersaline+mats.">Microbial lithification in marine stromatolites and hypersaline mats.</a> Trends Microbiol. 13, 429-438 (2005).</li><li>Steffan, R. J., Goksoyr, J., Boj, A. K., Atlas, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recovery+of+DNA+from+soils+and+sediments.">Recovery of DNA from soils and sediments.</a> Appl. Environ. Microbiol. 54, 2908-2915 (1988).</li><li>Lee, Y. K., Kim, H. W., Liu, C. L., Lee, H. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+method+for+DNA+extraction+from+marine+bacteria+that+produce+extracellular+materials.">A simple method for DNA extraction from marine bacteria that produce extracellular materials.</a> J. Microbiol. Methods. 52, 245-250 (2003).</li><li>Roose-Amsaleg, C. L., Garnier-Sillam, E., Harry, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+and+Purification+of+Microbial+DNA+from+Soil+and+Sediment+Samples.">Extraction and Purification of Microbial DNA from Soil and Sediment Samples.</a> Appl. Soil Ecol. 18, 47-60 (2001).</li><li>de Lipthay, J. R., Enzinger, C., Johnsen, K., Aamand, J., S&#248;rensen, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+DNA+extraction+method+on+bacterial+community+composition+measured+by+denaturing+gradient+gel+electrophoresis.">Impact of DNA extraction method on bacterial community composition measured by denaturing gradient gel electrophoresis.</a> Soil Biol. Biochem. 36, 1607-1614 (2004).</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>Kakirde, S. K., Parsley, L. C., Liles, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Size+does+matter:+Application-driven+approaches+for+soil+metagenomics.">Size does matter: Application-driven approaches for soil metagenomics.</a> Soil Biology &#38; Biochemistry. 42, 1911-1923 (2010).</li><li>Rodon, M. R., August, P. R., Bettermann, A. D., Brady, S. F., Grossman, T. H., Liles, M. R., Loiacono, K. A., Lynch, B. A., MacNeil, I. A., Minor, C., Tiong, C. L., Gilman, M., Osburne, M. S., Clardy, J., Handelsman, J., Goodman, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cloning+the+Soil+Metagenomic:+A+Strategy+for+Accessing+the+Genetic+and+Functional+Diversity+of+Uncultured+Microorganisms.">Cloning the Soil Metagenomic: A Strategy for Accessing the Genetic and Functional Diversity of Uncultured Microorganisms.</a> Appl. Environ. Microbiol. 66, 2541-2547 (2000).</li><li>Beja, O., Aravind, L., Koonin, E. V., Suzuki, M. T., Hadd, A., Nguyen, L. P., Jovanovich, S. B., Gates, C. M., Feldman, R. A., Spudich, J. L., Spudich, E. N., DeLong, E. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+Rhodopsin:+Evidence+for+a+New+Type+of+Phototrophy+in+the+Sea.">Bacterial Rhodopsin: Evidence for a New Type of Phototrophy in the Sea.</a> Science. 289, 1902-1906 (2000).</li></ol>

No conflicts of interest declared.

Given that total cell removal from complex and highly diverse microbial mat samples is not practical, the primary concern is how well the extracted cells represent the overall microbial mat community. In a previous study, PCR-DGGE analysis of microbial 16S rRNA genes showed that the five cell removal steps used in this protocol extracts cells that are representative of the overall microbial mat community7. The actual number of cell extraction steps required to provide a cell pellet that is representative of th...

<table border="1">
	<tbody>
		<tr>
			<th>Name of reagent</th>
			<th>Company</th>
			<th>Catalogue number</th>
			<th>Comments</th>
		</tr>
		<tr>
			<td>&beta;-mercaptoethanol</td>
			<td>Sigma-Aldrich</td>
			<td>M3148</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Polyethylene glycol 8000</td>
			<td>Promega</td>
			<td>V3011</td>
			<td>20% in 1.2 M NaCl</td>
		</tr>
		<tr>
			<td>Potassium acetate</td>
			<td>Fisher Scientific</td>
			<td>&nbsp;</td>
			<td>Fisher Scientific</td>
		</tr>
		<tr>
			<td>Quant-iT dsDNA Assay kit</td>
			<td>Invitrogen</td>
			<td>Q33130</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>RNase</td>
			<td>Epicentre </td>
			<td>MRNA092</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>BDH Chemicals</td>
			<td>BDH8014</td>
			<td>Appropriate conc.</td>
		</tr>
		<tr>
			<td>Sodium Dodecyl Sulfate</td>
			<td>Fisher Scientific</td>
			<td>03-500-509</td>
			<td>10% in water</td>
		</tr>
		<tr>
			<td>sodium hexametaphosphate</td>
			<td>EMD Chemicals</td>
			<td>SX0583-3</td>
			<td>2% in water</td>
		</tr>
		<tr>
			<td>TBE</td>
			<td>Fisher Scientific</td>
			<td>BP1333-1</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>CHEF Mapper XA System</td>
			<td>Bio-Rad Laboratories</td>
			<td>170-3670</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>NanoDrop 1000 spectrophotometer</td>
			<td>Thermo Scientific</td>
			<td>ND-1000</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Vortexer</td>
			<td>Scientific Industries Inc.</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Ultraviolet Crosslinker</td>
			<td>UVP</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Waring blender</td>
			<td>Waring laboratory </td>
			<td>LB10S</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

extraction of high molecular weight dna from microbial mats

Successful and accurate analysis and interpretation of metagenomic data is dependent upon the efficient extraction of high-quality, high molecular weight (HMW) community DNA. However, environmental mat samples often pose difficulties to obtaining large concentrations of high-quality, HMW DNA. Hypersaline microbial mats contain high amounts of extracellular polymeric substances (EPS)1 and salts that may inhibit downstream applications of extracted DNA. Direct and harsh methods are often used in DNA extraction from refractory samples. These methods are typically used because the EPS in mats, an adhesive matrix, binds DNA2,3 during direct lysis. As a result of harsher extraction methods, DNA becomes fragmented into small sizes4,5,6.
The DNA thus becomes inappropriate for large-insert vector cloning. In order to circumvent these limitations, we report an improved methodology to extract HMW DNA of good quality and quantity from hypersaline microbial mats. We employed an indirect method involving the separation of microbial cells from the background mat matrix through blending and differential centrifugation. A combination of mechanical and chemical procedures was used to extract and purify DNA from the extracted microbial cells. Our protocol yields approximately 2 &mu;g of HMW DNA (35-50 kb) per gram of mat sample, with an A260/280 ratio of 1.6. Furthermore, amplification of 16S rRNA genes7 suggests that the protocol is able to minimize or eliminate any inhibitory effects of contaminants. Our results provide an appropriate methodology for the extraction of HMW DNA from microbial mats for functional metagenomic studies and may be applicable to other environmental samples from which DNA extraction is challenging.

Watch this Scientific Journal Video about Extraction of High Molecular Weight DNA from Microbial Mats at JoVE.com

Extraction of High Molecular Weight DNA from Microbial Mats

We provide an improved protocol for extracting high molecular weight DNA from hypersaline microbial mats. Microbial cells are separated from the mat matrix prior to DNA extraction and purification. This enhances the concentrations, quality, and size of the DNA. The protocol may be used for other refractory samples.

Successful and accurate analysis and interpretation of metagenomic data is dependent upon the efficient extraction  of high-quality, high molecular weight ...

extraction-of-high-molecular-weight-dna-from-microbial-mats

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19.4K Views.  Arnold School of Public Health, University of South Carolina. We provide an improved protocol for extracting high molecular weight DNA from hypersaline microbial mats. Microbial cells are separated from the mat matrix prior to DNA extraction and purification. This enhances the concentrations, quality, and size of the DNA. The protocol may be used for other refractory samples.