NEW DOUBLE-STAINING TECHNIQUE FOR RNA AND DNA MEASUREMENT IN MARINE-PHYTOPLANKTON

The use of RNA:DNA ratios as a biochemical indicator is hampered by the lack of simple and reliable methods for routine work. The technique presented here approaches this problem by using 2 fluorochromes: Hoechst 33258, which specifically reacts with DNA, and Thiazole Orange, which allows total nucleic acid estimation. Samples are homogenized in Tris-Ca2+ buffer which is also used in the fluorometric analysis. Subsequently, these fluorochromes are added to different subsamples of the same nucleic acid extract. Several extraction and analysis techniques were tested and an optimized procedure is described. The technique is simple and more sensitive than previously described methods for the determination of RNA and DNA in phytoplankton.