M A S McMahon1, D A McDowell, I S Blair. 1. Food Microbiology Research Group, University of Ulster, Newtownabbey BT37 OQB, UK. ma.mcmahon@ulster.ac.uk
Abstract
AIMS: To describe the interactions of imposed osmotic and nutritional stress on the morphology of stationary and exponential phase S. Virchow cells. METHODS AND RESULTS: This study examined the morphology and viability of osmotically stressed exponential and stationary phase cultures of Salmonella Virchow under nutritionally deficient and competent conditions. In addition to normal morphology, salt-stressed cultures exhibited filamentous and spherical morphotypes, which were capable of reversion to normal morphology on stress removal. Proportions of atypical morphotypes were influenced by the phase of growth when the stress was applied. Salt-stressed exponential phase populations contained 54% filamentous, 30% spherical forms, salt-stressed stationary phase populations contained 16% filamentous, 79% spherical forms. Proportions of morphotypes were also influenced by the nutrient status of the medium, but not by metabolic by-products. CONCLUSIONS: Development of a range of morphotypes in response to stress (osmotic/nutritional), may offer population level advantages, increasing the survival potential of the population. SIGNIFICANCE AND IMPACT OF STUDY: The application of sublethal concentrations of salt may stimulate S. Virchow morphotype diversity, improving survival and rates of poststress recovery.
AIMS: To describe the interactions of imposed osmotic and nutritional stress on the morphology of stationary and exponential phase S. Virchow cells. METHODS AND RESULTS: This study examined the morphology and viability of osmotically stressed exponential and stationary phase cultures of Salmonella Virchow under nutritionally deficient and competent conditions. In addition to normal morphology, salt-stressed cultures exhibited filamentous and spherical morphotypes, which were capable of reversion to normal morphology on stress removal. Proportions of atypical morphotypes were influenced by the phase of growth when the stress was applied. Salt-stressed exponential phase populations contained 54% filamentous, 30% spherical forms, salt-stressed stationary phase populations contained 16% filamentous, 79% spherical forms. Proportions of morphotypes were also influenced by the nutrient status of the medium, but not by metabolic by-products. CONCLUSIONS: Development of a range of morphotypes in response to stress (osmotic/nutritional), may offer population level advantages, increasing the survival potential of the population. SIGNIFICANCE AND IMPACT OF STUDY: The application of sublethal concentrations of salt may stimulate S. Virchow morphotype diversity, improving survival and rates of poststress recovery.