Assessing the suitability of a molecularbiological method to characterise the microbial populations in groundwater

A molecularbiological technique was used to characterise the bacterial comm unity structure of groundwater habitats. This method consists of the isolat ion of bacterial DNA from the samples, amplification of 16S rDNA by PCR (po lymerase chain reaction), and separation of the amplified DNA. by DGGE (den aturing gradient gel electrophoresis). By using more specific primer combin ations in the PCR instead of universal eubacterial primers, also groups of microorganisms (Proteobacteria, sulfate reducer, Archaea) were determined. The resulting DGGE patterns that reflect the microbial diversity are compar ed and differences or similarities evaluated. In the present studies, groun dwater from different sites (bank filtrate, artificially recharged groundwa ter; and natural groundwater) and with changing redox milieus (aerobic, ana erobic) were investigated as well as the solid aquifer material. Besides, s amples were taken from the different stages of artificial groundwater recha rge, i.e., from surface water to the drain tile. Samples from groundwater derived from sites with different hydrogeochemical or hydrological conditions like bank filtrate and recharged groundwater re vealed great differences in DGGE patterns indicating a characteristic speci es composition in these habitats, while samples taken at different times fr om the same groundwater showed only small seasonal variations. Clearly diff erent patterns were also found for groundwater and the adjacent solid mater ial as well as for anaerobic and aerobic groundwaters. Looking at artificia l groundwater recharge, almost identical patterns were found in raw water a nd samples from gravel and sand filtration. DGGE patterns from the resultin g groundwater indicated a total change in community structure during underg round passage. By using group specific primers, Desulfovibrionaceae, Desulfobacteriaceae, and Archaea could be detected in anaerobic groundwaters. The molecularbiological approach described here gives an increasingly compr ehensive and more precise picture of the microbial population of different environments. It is especially suitable to compare the community structure from different habitats or to analyse changes for example due to environmen tal stress at the same site.