Effect of Environmental Factors On the Recovery of Extracellular DNA.

Molecular techniques are now being widely used in the study of water microbiology. Because of the low microbial biomass in water, water samples are often concentrated by filtrating though membrane filters to get sufficient material to start with. Due to the presence of extracellular DNA (eDNA) that is often abundant in water environment, this filtration step will possibly recover considerable amount of eDNA and consequently bias molecular detection result. Currently very limited information is available in this aspect. In this study our objective is to evaluate the effect of environmental factors on the recovery of eDNA during the filtration steps. Linearized plasmid DNA containing full length of Cryptosporidium parvum 18S rRNA gene fragments were spiked into water solution with different total suspended solid content, pH value and ionic strength were filtrated through membrane filter of different pore size, filter were subjected to DNA extraction and DNA quantified with qPCR using C. parvum 18S rRNA gene specific primers and probe. the results indicated that the composition of total suspended solid significantly impact the recovery of eDNA by filtration. Recovery of eDNA is also substantially affected by solution pH and ionic strength. The significance of the results is also discussed.