Further progress in the development of a standardised method for testing yeast–bacteria interaction is being made, enabling comparative measurement of bacterial growth in fermented chemically defined test media and non-fermented chemically defined reference wine (Costello et al., submitted for publication). In this approach, a dual-purpose synthetic medium (pH 3.5) was formulated for the preparation of both a synthetic grape juice medium, and a (non-fermented) synthetic wine, based on the medium formulations published by Henschke and Jiranek (1993) and Liu et al. (1995).