Abstract
Listeria monocytogenes
is a food-borne pathogen that has been implicated in many outbreaks associated with ready-to-eat products.
Listeria
adjusts to various stresses by adjusting its membrane fluidity, increasing the uptake of osmoprotectants and cryoprotectants, and activating the σ
B
stress factor. The present work examines the regulation of membrane fluidity through direct measurement based on fluorescent anisotropy. The membrane fluidities of
L. monocytogenes
Scott A, NR30, wt10403S, and cld1 cells cultured at 15 and 30°C were measured at 15 and 30°C. The membrane of the cold-sensitive mutant (cld1) was more rigid than the membranes of the other strains when grown at 30°C, but when grown at 15°C, it was able to adjust its membrane to approach the rigidity of the other strains. The difference in rigidities, as determined at 15 and 30°C, was greater in liposomes than in whole cells. The rates of fluidity adjustment and times required for whole cells to adjust to a different temperature were similar among strains but different from those of liposomes. This suggests that the cells had a mechanism for homeoviscous adaptation that was absent in liposomes.