PUTATIVE ROLE OF THE ALTERNATIVE SIGMA FACTOR, SIGB, IN SURVIVAL OF LISTERIA MONOCYTOGENES 568 DURING DESICCATION ON STAINLESS STEEL SURFACES

Abstract

Listeria monocytogenes is a foodborne bacterial pathogen that colonises and persists in the food processing environment causing cross-contamination of processed foods, including ready-to-eat meat products. I hypothesised that survival of L. monocytogenes during desiccation on stainless steel is influenced by the alternative sigma factor (?B), which is a transcriptional regulator of stress responses. The objective of this research was to test whether ?B contributes to the survival of L. monocytogenes during desiccation, through the characterization of a sigB deletion mutant and its desiccation behaviour. Deletion of sigB reduced Listeria’s survival during desiccation in osmolyte- and nutrient-limited conditions. Pre-culturing with osmolytes or adding osmolytes during desiccation, increased survival. RT-PCR results indicated that at high osmolarity transcription of opuCA (encoding an osmolyte carnitine transporter) was controlled by ?B. I concluded that SigB is partly involved in the short-term survival of L. monocytogenes during desiccation, but, ?B-independent systems mediate survival during long-term desiccation.