The pattern of pleiomorphism in stressed Salmonella Virchow populations is nutrient and growth phase dependent.
OBJECTIVE
To describe the interactions of imposed osmotic and nutritional stress on the morphology of stationary and exponential phase S. Virchow cells.


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.


CONCLUSIONS
The application of sublethal concentrations of salt may stimulate S. Virchow morphotype diversity, improving survival and rates of poststress recovery.
McMahon
M A S
MA
Food Microbiology Research Group, University of Ulster, Newtownabbey BT37 OQB, UK. ma.mcmahon@ulster.ac.uk
McDowell
D A
DA
Blair
I S
IS
D003470:Culture Media; D008855:Microscopy, Electron, Scanning; D009997:Osmotic Pressure; D019779:Salmonella enterica / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure*; D012965:Sodium Chloride / Q000494:pharmacology
D003470:Culture Media; D012965:Sodium Chloride