Physicochemical surface properties of five Listeria monocytogenes strains from a pork-processing environment in relation to serotypes, genotypes and growth temperature

Physicochemical surface properties, related to electrostatic, van der Waals and Lewis acid-base interactions, of five Listeria monocytogenes strains i solated from pork-processing environments were determined after two subcult ures at 37 degrees C and a final culture at three temperatures: 37, 10 and 4 degrees C. Three strains (Lm1, Lm114 and Lm191) were genetically related while two were unrelated (Lm25 and Lm74) according to ApaI-macrorestriction and pulsed-field gel electrophoresis (PFGE) typing. Listeria monocytogenes cell surfaces were generally negatively charged rega rdless of pH and tended to be hydrophilic due to a basic character. However , variable physicochemical surface properties of the five Listeria monocyto genes isolates were observed after growth at 37 degrees C. After growth at 10 degrees C, the three genetically related isolates exhibited similar surf ace properties and were slightly more hydrophilic and basic than the others . After growth at 4 degrees C, the five isolates displayed the same weak af finity for all kinds of solvents and low electrophoretic mobility values. A sharp decrease of temperature and subsequent growth of various Listeria m onocytogenes strains resulted in loss of the physicochemical surface proper ty variability, which may suggest the role of common chill adaptation mecha nisms affecting surface properties.