Use of the SYBR Green I fluorescent dye and a centrifugal filter device for rapid determination of dissolved DNA concentration in fresh water

A rapid fluorometric assay using the fluorescent dye SYBR Green I was established to determine the concentration of dissolved nucleic acids in fresh water. The sensitivity of SYBR Green I to double stranded DNA (dsDNA) (lambdaHind III digest) was as low as 50 pg, 200 times more sensitive than Hoechst 33258. SYBR Green I bound to dsDNA emitted 10 times stronger fluorescence than when bound to single stranded DNA or RNA, indicating its selectivity for dsDNA measurement. The dissolved DNA (dDNA) concentration in fresh water determined using SYBR Green I was almost the same as that obtained using Hoechst 33258. This suggests that the dDNA measured by SYBR Green I is comparable to that determined by Hoechst 33258 in previous studies. To reduce preparation time, the dDNA in lake water filtrate was precipitated by ethanol and purified using a centrifugal filter device. The overall preparation process takes only a few hours and requires only 10 ml of water. The process described here may, therefore, facilitate 'same day' measurement of dDNA dynamics in freshwater environments.