Comparative assessment of methods for metagenomic DNA isolation from soils of different crop growing fields

The isolation of good quality metagenomic DNA from diverse soil, in appreciable amount, is a prerequisite for metagenomics. The availability of commercial kits for isolation of genomic DNAs from soil has drastically expedited the application of metagenomics approach for identifying novel sources of industrially important enzymes. The quantitative and qualitative assessment of metagenomic DNA isolated using either the manual method or the kit-based method should be performed prior to its use in downstream applications. The metagenomic DNA isolated from six different soil samples, using three methods, were analyzed in terms of yield, quality and downstream application as template for PCR amplification. The yield of DNA was approximately 3.52, 7.35, and 232.42 μg of DNA per gram of soil sample for the kit-based method, kit-modified method, and manual method, respectively. The manual method seems to be promising based on better yield and lesser humic acid content than the other two methods. The maximum yield was obtained in the soil collected from teak forest with all the three methods, indicating maximum microbial content and diversity. Furthermore, in terms of its suitability as template DNA for PCR amplification using 16S RNA primer, all methods are equally well. Thus, comparative assessment of three methods revealed suitability of manual method based on DNA yield and humic acid content, which could be important for many downstream applications like library preparations during metageomics approach.