Abstract:
The present study investigated the influence of low-shear modeled microgravity (LSMMG) conditions on Listeria
monocytogenes stress response (heat, cold, and acid), membrane fatty acid composition, and virulence potential
as well as stress-/virulence-associated gene expression. The results showed that LSMMG-cultivated cells had
lower survival rate and lower D-values under heat and acid stress conditions compared to cells grown under
normal gravity (NG). Interestingly, the cold resistance was elevated in cells cultivated under LSMMG conditions
when compared to NG conditions. A higher amount of anteiso-branched chain fatty acids and lower ratio of iso/
anteiso were observed in LSMMG cultured cells, which would contribute to increased membrane fluidity. Under
LSMMG conditions, upregulated expression of cold stress-related genes (cspA, cspB, and cspD) was noticed but
no change in expression was observed for heat (dnaK, groES, clpC, clpP, and clpE) and acid stress-related genes
(sigB). The LSMMG-grown cells showed inferior virulence capacity in terms of infection, cell cycle arrest, and
apoptosis induction in Caco-2 cells compared to those grown under NG conditions. Approximately 3.65, 2.13,
4.02, and 2.65-fold downregulation of prfA, hly, inlA, and bsh genes, respectively, in LSMMG-cultured cells
might be the reason for reduced virulence. In conclusion, these findings suggest that growth under LSMMG
conditions stimulates alterations in L. monocytogenes stress/virulence response, perhaps due to changes in lipid
composition and related genes expression.
