Gamma Irradiation Effects on Fatty Acid Profiles, Adhesion, Plasmid Stability, and Secreted Proteins in Shigella: In Silico Insights into Post-Irradiation Virulence

This study investigated the adaptive mechanisms of Shigella sonnei ATCC25931 in response to gamma irradiation stress (0.5 and 1 kGy), with a specific focus on the involvement of fatty acids (FAs) in membrane lipid composition remodeling, adherence, and extracellular proteins. The results demonstrated a notable enhancement in cell hydrophobicity and adherence to KB cells following irradiation, although the invasion rate exhibited a decline from 14% to 2.35% at 1 kGy. Furthermore, gamma irradiation induced notable alterations in fatty acid (FA) composition, characterized by a pronounced reduction in the unsaturated/saturated FA ratio. Additionally, the plasmid profiles revealed the loss of several original plasmids after gamma irradiation. The alterations in extracellular proteins were observed through SDS-PAGE, which demonstrated a reduction in expression at 1 kGy. Furthermore, a molecular docking analysis indicated that fatty acids play a role in inhibiting VirF, a key regulator of Shigella virulence. The least effective inhibitor was capric acid, while linoleic and gamma-linolenic acids formed the most stable inhibitory complexes, which prevented VirF from activating the virulence system. These alterations in fatty acids, plasmids, and extracellular proteins constitute adaptive responses to irradiation-induced stress.