Recent ecological surveys indicate that the wine yeast Saccharomyces cerevisiae may be isolated with extreme difficulty from natural substrates, such as vineyard soil or the surface of mature grapes, conventionally believed to be its elected habitat. Conversely, it is amply demonstrated that its preferential location as the only fermenting colonizer is the surfaces of the wineries. Non-conventional methods for the separation, isolation, and enumeration of yeast cells from mature grapes of different varieties produced additional and unequivocal evidence on the numerical inconsistency of S. cerevisiae cells in nature. The taking over of musts by the natural yeast flora was also followed in microfermentations.