Sample Collection and DNA Isolation from Environmental Samples

DNA libraries and to done directly functional genes from natural samples. The knowledge of sequence information prior to cloning is not required. Another advantage is that existing environmental libraries can be employed for screening of various targets. 

Sample Collection and DNA Isolation from Environmental Samples 

The cloning of functional genes from natural microbial consortia is dependent on the high quality of the extracted and purified environmental DNA since the enzymatic modifications required during the cloning steps are sensitive to contamination by various biotic and abiotic components that are present in environmental ecosystems. For example, extraction of DNA from soils always results in coextraction of humic substances, which interfere with restriction enzyme digestion and PCR amplification and reduce transformation efficiency and DNA hybridization specificity [19 -22], Therefore, extraction methods have been developed to remove or minimize contamination of the purified DNA by humic or other interfering substances. Several protocols for the isolation of bacterial community DNA from various environmental samples have been reported in recent years. These methods are based either on re- 

Cell lysis and preparation of crude DNA by high-salt extraction in the presence of CTAB and proteinase K and then by treatment with SDS 

Removal of coextracted substances by chromatography on silica gel or anion-exchange columns 

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