Desiccation Tolerance in Listeria monocytogenes: Mechanisms and Importance for Food Safety

Abstract

This study examined some of the environmental, physiological, and genetic factors or mechanisms which contribute to L. monocytogenes’ desiccation survival under food processing conditions. Desiccation experiments were carried out on stainless steel coupons stored at 43% RH, 15°C. The level of initial contamination had no impact (p>0.05), whereas the presence of a mature biofilm, prior osmoadaptation, and the presence of salt (5%) and lard (20-60%) on the SS coupons significantly (p<0.05) increased the bacterium’s desiccation survival. An Lm568 transposon mutant library was constructed to screen for novel genes involved in desiccation survival. Fifteen tolerant and 16 sensitive desiccation mutants were sequenced. Interrupted genes involved in motility and FA membrane modification were the most common in tolerant mutants whereas energy and membrane transport related genes were the most recognized in sensitive mutants. Lastly, a spontaneous desiccation resistant Lm568 variant was isolated, emphasizing the importance of understanding desiccation tolerance for food safety.