Total counts, culturable and viable, and non-culturable microflora of a French mineral water: a case study

The changes in bacterial counts during the storage of a natural mineral water from a French spring were studied. Samples were taken from the spring and the bottling line. Viable cultivable (VC) bacteria were counted on R2A medium. Total counts, viable and dead bacteria were counted using the LIVE/DEAD Bac Light VIABILITY kit and epifluorescence microscopy. Viable but non-cultivable (VNC) bacteria were estimated by difference between viable and VC counts. Isolates were clustered by phenotype. The microflora in the spring water increased from < 10-3 x 10(5) bacteria ml-1 after 6 d in storage and then stabilized. Mechanical bottling increased the allochthonous bacteria in the water that stabilized at 10(5) bacteria ml-1. Maximal growth is controlled by the low concentration of nutrients in the mineral water and the lysis of dead cells. The allochthonous bacteria came from the aquifer and colonized the filling line. The changes in the VC and VNC populations showed that the bacteria used starvation-survival and entry into the VNC state to adapt to the bottling stress and the enclosed oligotrophic environment.