IngentaConnect Role of Sigma B Factor in the Alkaline Tolerance Response of List...

Authors: Giotis, Efstathios S.¹; Julotok, Mudcharee²; Wilkinson, Brian J.²; Blair, Ian S.¹; McDowell, David A.¹

Source: Journal of Food Protection®, Volume 71, Number 7, July 2008 , pp. 1481-1485(5)

Publisher: International Association for Food Protection

Abstract:

Many of the considerable abilities of Listeria monocytogenes to persist and grow in a wide range of adverse environmental conditions are thought to be at least partly under the control of the alternative sigma factor (σ^B), encoded by the sigB gene. However, little is known about the role of this master regulon in the impressive ability of Listeria to persist and grow under conditions of alkaline pH. In this study, Northern blot analysis of parent Listeria mRNA revealed that alkali adaptation (pH 9.5 for 1 h) significantly increased the expression of sigB-derived mRNA. The study included a comparison of the relative survival of mid-exponential populations of adapted and nonadapted parent type (σ^B expressing) and mutant (not σ^B expressing, ΔsigB) Listeria strains during subsequent alkaline (pH 12.0), osmotic (25% NaCl, wt/vol), or ethanol (16.5%) stress. Alkali-adapted parent strains were more resistant to pH 12.0 than were adapted ΔsigB type strains, but both alkali-adapted parent and ΔsigB strains were more resistant to pH 12.0 than were nonadapted strains. Alkali-adapted parent strains were more resistant to osmotic stress than were adapted ΔsigB type strains. No significant differences in viability were observed between alkali-adapted parent and ΔsigB strains after ethanol stress, suggesting that cross-protection against osmotic stress is mediated by σ^B whereas cross-protection against ethanol is σ^B independent. Overall, alkali-induced cross-protection against osmotic and ethanol challenges may have serious implications for food safety and human health because such stress conditions are routinely used as part of food preservation and surface cleaning processes.

Document Type: Research article

Affiliations: 1: Food Microbiology Research Unit, University of Ulster, Northern Ireland BT37 0QB, United Kingdom 2: Microbiology Group, Department of Biological Sciences, Illinois State University, Normal, Illinois 61790-4120, USA

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Role of Sigma B Factor in the Alkaline Tolerance Response of Listeria monocytogenes 10403S and Cross-Protection against Subsequent Ethanol and Osmotic Stress