QIAamp DNA Stool Mini Kit From Qiagen

With the evolution of environmental microbiology, microbial ecology and lately metagenomics, the need for a rapid, simple and efficient large-scale DNA extraction method from various environmental samples has increased. But, amplification of DNA (using PCR) from these natural sources is often inhibited by co-purified contaminants. There is a galore of reports on various methods adopted for DNA extraction from environmental samples; however, they are either cumbersome or inefficient. QIAamp DNA Stool Mini Kit from Qiagen is designed for rapid purification of total DNA from stool. However, this kit can be successfully used to extract bacterial DNA from various environmental samples. In our laboratory, we have used it for samples ranging from soil, sludge, wastes and wastewater to fermentation broth with good results.

The key advantage of QIAamp DNA Stool Mini Kit is adsorption of DNA-damaging substances and PCR inhibitors present in the sample by InhibitEX. The kit comes with InhibitEX tablets which are convenient to use. The protocol is almost as simple as typical DNA extraction kits. Within 45-60 min, the DNA is ready for PCR or any further use. The amount of DNA output is directly proportional to the bacterial population and inversely proportional to the amount of inorganic material present in the sample. The kit can be used for both smaller and larger numbers of samples; it is also equally suitable for both liquid and solid samples. The yield of the DNA is 10-100 ug depending on the sample. To evaluate the purity of the extracted DNA, absorbance ratios at 260 nm/230 nm (DNA/humic acids) and 260 nm/280 nm (DNA/protein) can be determined. The DNA obtained is PCR ready and efficiency of the PCR is above 90% with reproducible results. A minimum amount of DNA eluate can give good PCR outcome and adding BSA to a final concentration of 0.1 ug/ul to the PCR mixture is recommended for better results. The DNA obtained can be stored at -20ºC for a considerable period (several months), with no loss in performance even after freeze-thaw cycles.

There is no special sample preparation or pretreatment is required. Both fresh and frozen samples can be used for sufficiently good quality DNA provided storage conditions are standard. Most kits available in the market do not particularly take care of the inhibitors and therefore, the DNA has to be treated further to sequester these inhibitors. The QIAamp Kit eliminates this post-treatment which can reduce the final DNA yield. The convenient spin procedure is designed to ensure no sample-to-sample cross contamination and safe handling of potentially infectious samples. The kit comes with most things required for the procedure. Unlike most methods which require a beat-beater or a sonicator, this method suits any typical microbiological lab having simple microcentrifuge, waterbath and vortexer. The method also eliminates the risk of DNA shear as encountered in other methods thereby resulting in high molecular weight and intact DNA (above 20 kb).

If you are looking for DNA from soil, several kits have been launched lately, but none is as efficient with such diverse samples as the QIAamp DNA Stool Mini Kit. Particularly for microbial ecologists targeting different kinds of environmental samples, this is a recommended product. Price of the kit is also quite reasonable compared to other competitive kits available.