The relative amounts of PCR products obtained for
nirS, nirK and nosZ in the environmental samples were
estimated by comparing band intensities on agarose gels.
In order to get approximately the same amount from
each sample, the amplicons were concentrated through
freeze-drying (3101 mbar and )40 to )50 C;Edwards Modulyo Freeze Dryer, BOC Edwards,
Crawley, UK) to approximately 1/5 of the original volume
before DGGE analysis