Isolation of PCR-quality Genomic DNA from Soils Impacted with Extra Heavy Crude Oil

For the study of microbial communities in samples of soils impacted with extra heavy crude oil, it is necessary to perform molecular analyses. Due to the difficulty of oil matrix handling, there are very few protocols reported in writing. Also, one can only observe a very low concentration of DNA. That's why it is required to have an effective protocol to conduct studies in this type of matrix. This protocol includes steps of cell lysis by saline buffer with ionic/non-ionic detergents, and enzymatic digestion with lysozyme and proteases, complemented with organic extraction and alcohol precipitation. Additionally, it requires purification to eliminate the inhibitory substances of the extract that cause PCR inhibition. The method of DNA extraction proposed in this study is easy to handle and low cost. It allows the extraction of DNA from different bacteria and fungi, associated with soil contaminated with extra heavy crude.