Comparison of the spatial homogeneity of physico-chemical parameters and bacterial 16S rRNA genes in sediment samples from a dumping site for dredging sludge

The homogeneity of the microbial community structure of a sediment landfill was examined by a culture-independent method and compared with physico-che mical parameters, i.e. organic matter, CaCO3 content, pH, and texture. Tota l genomic DNA was extracted from samples derived from different places and depths. After amplification with two different primer sets of partial bacte rial 16S rRNA genes, the products were separated by denaturing gradient gel electrophoresis (DGGE). The DGGE fingerprints of different sediment sample s taken in regular patterns at the same depth were similar, which indicates a spatial homogeneity in the numerically dominant bacterial populations in a landfill over 10,000 m(2) in size. In a vertical column of approx. 10 m, only some differences in a few bands of the bacterial community structure were observed between samples taken from different depths. This DNA homogen eity coincided with a similar homogeneity of the physico-chemical parameter s in the landfill at this site. Nevertheless, the DGGE technique revealed s mall differences in less prominent bacteria and was capable of separating t he upper and lower samples of one column into two clusters. It therefore se ems more sensitive than the physico-chemical approach for characterising th e homogeneity of an environmental habitat.