Molecular fingerprinting of bacterial populations in groundwater and bottled mineral water

Monitoring the hygienic quality of drinking waters by determining the conce ntration of fecal indicators with traditional plate count techniques suffer s from important drawbacks. In this work, the potential of PCR-DGGE (polyme rase chain reaction - denaturing gradient gel electrophoresis) analysis of 16S rDNA genes to fingerprint the bacterial populations of mineral water an d groundwater was investigated. A rapid and simple pretreatment to concentr ate and release bacterial DNA prior to PCR was explored. This pretreatment was successful for commercially bottled mineral water. For groundwater, an additional resuscitation step was required to obtain a PCR signal. It was c lear that the groundwater under scrutiny contained a more diverse bacterial community than the mineral water. A comparison was made between four kinds of mineral waters and one sample of groundwater using the developed proced ures. For each kind of water, bacterial populations cultured on R2A plates were also subjected to PCR-DGGE. Comparison of the fingerprints of the plat ed samples and the original samples suggested the presence of viable but no nculturable bacteria in the waters. The obtained cluster dendrogram indicat ed that each kind of water was characterized by a specific molecular finger print. The sensitivity of the whole of the procedure was between 10(4) and 10(5) cfu ml(-1) as determined using a pure culture of Escherichia coli. Th e described PCR-DGGE method can constitute the basis of a new and interesti ng strategy to monitor in a relatively rapid way (less than 24 h) the bacte rial quality of waters such as mineral water, groundwater and certain types of reclaimed water.