Concentration and susceptibility of dissolved DNA for enzyme degradation in lake water - Some methodological remarks

Abstract

This paper discusses the methodology for determination of dissolved DNA concentration by means of direct DAPI staining of water samples and compares it with the data obtained by the method of dissolved DNA precipitation (in 0.2 μm water filtrates) with the use of cetyltrimethyl-ammonium bromide (CTAB) and DAPI staining. The samples were collected from lakes of varying trophic states. Enzymatically hydrolysable DNA (EH-DNA) was estimated as the difference between the concentration of the DNA in samples without and with DNAse treatment. Concentrations of enzymatically hydrolysable DNA determined by the enzymatic method were 27 to 54% lower than those measured by CTAB-DNA precipitation and DAPI staining. Enzymatically hydrolysable DNA concentrations increased with the trophic state of the lake and correlated positively with algal pigment concentrations and bacterial numbers. The contribution of phosphorus that can be enzymatically liberated from extracellular DNA to the total organic phosphorus concentration in lake water samples varied from 11% (oligo/mesotrophic lake) to 27.6% (hypertrophic lake).