The extreme extent of resistance of Z. bailii to weak-acid preservatives was shown to be due to the presence of an extended “tail” of highly resistant cells.
The proportion of the resistant sub-population declined with increased weak-acid concentration, resulting in survival of a few cells in high concentrations of sorbic acid (Fig. 1a).
It was found that the proportion of resistant cells in the population varied considerably
between different experiments. The cause of this variation was identified as the age of the starter culture.
A detailed analysis of populationdiversity in sorbic acid resistance (Fig. 1a) showed a considerable difference between exponentially-growing cells (38-hour starter culture)
and a post-exponential, stationary-phase culture (52-hour).