Community structures of different groundwater habitats investigated using methods of molecular biology

The degradation of pollutants in groundwater and aquifers depends on microb iological and hydrogeochemical processes. To understand the transport and f ate of anthropogenic compounds during bank filtration and artificial rechar ge of groundwater it is necessary to gain more information about the struct ure of microbial populations in these systems. The population structure of aerobic, anaerobic groundwater habitats and of water samples during artific ial groundwater recharge was examined by 16S rDNA based analysis. Water and sediment samples were collected from a groundwater catchment area with art ificial groundwater recharge near the river Ruhr in NW-Germany. 16S rRNA genes of mixed bacterial DNA from different samples were amplified by PCR (polymerase chain reaction) with eubacterial primer sequences. To r eveal eubacterial population structure amplified PCR-products were separate d by DGGE (denaturing gradient gel electrophoresis) on the basis of melting domain structure and nucleotide composition. DGGE patterns of groundwater enrichment cultures and groundwater samples were compared to demonstrate di fferences between the use of cultivation dependent and molecularbiological approaches. The DGGE pattern of groundwater is very complex and differs sig nificantly from DGGE patterns of groundwater enrichment cultures characteri zed by a small number of distinct bands. This shows the small quantity of c ulturable microorganism in groundwater ecosystems. Aerobic and anaerobic gr oundwater and sediment samples differ markedly in their DGGE profiles. Diff erent hydrogeochemical zones of this groundwater catchment area are mirrowe d by distinct DGGE patterns indicating changes in microbial community struc ture. Analysis of bacterial population structure in the course of artificia l groundwater recharge shows identical DGGE patterns comparing surface wate r samples to samples taken before gravel prefiltration and before sand filt ration. In contrast the DGGE pattern of artificial recharged groundwater di ffers markedly, indicating significant changes in microbial population duri ng underground passage.