Analysis of soil and bacterioplankton community DNA by melting profiles and reassociation kinetics

Whole-community DNA was extracted from two pasture soils, the cultivable and directly extractable bacterial subsets of one of the soils, and two aquatic bacterioplankton communities. The percent guanine+cytosine (%G+C) base distribution, derived using thermal denaturation profiles, and parameterised using a generalised logistic equation, varied markedly between the samples. Bacterioplankton communities carried a more even distribution of %G+C than the soil communities, which had higher median %G+C. The directly extracted soil bacterial fraction had the highest median %G+C. There was a distinct trend of increasing complexity, measured using reassociation kinetics, between cultivable, extractable and total soil community DNA. Bacterioplankton communities were of a similar order of complexity to the cultivable soil bacterial fraction.