Gene expression variability distinguishes yeast strains. Expression of genes involved in flocculation, transport and cell division distinguished strains J940047 and S288C from the environmental and commercial strains. When compared to the environmental strains (06L3FF02, 06L6FF20) and the commercial strains (AEB Fermol Rouge, Lalvin ICV D254 and Lalvin EC-1118), strains J940047 and S288C showed higher relative transcript abundance for genes included in cluster VIII of Figure 2A throughout fermentation. Among these were Ty, flocculation (FLO5 and FLO9), transport (SEO1 and SUL1), cell wall organization and biogenesis (EXG2) and meiosis (RME1 and CEP3) genes. All strains up-regulated these genes at the transition from exponential to stationary phase, but the increase in expression was more pronounced in the case of strains J940047 and S288C. Only the genes with annotated functions are depicted in the heat map, for comparison.