State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbiology Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou 510070, China. Electronic address: [Email]
Cronobacter species are a group of opportunistic food-borne pathogens that cause rare but severe infections in neonates. Tolerance to environmental stress in Cronobacter is known; however, factors involved in oxidative stress are undefined. In this study, Cronobacter sakazakii survival, cellular morphology, and biofilm formation in response to oxidative stress were evaluated between the wild type (WT) and an outer membrane protein W (OmpW) mutant. The survival rates of ΔOmpW strain after treatment with 1.0 and 1.5 mM hydrogen peroxide were significantly reduced compared with those of WT. Morphological changes, including cell membrane damage and cell fragmentation, in ΔOmpW were more predominant than those in WT. By crystal violet staining, we also observed increased biomass in ΔOmpW biofilms as compared with WT following treatment with 0.5 and 1.0 mM H2O2. Biofilms using scanning electron microscopy and confocal laser scanning microscopy further confirmed the structural changes of biofilms between WT and ΔOmpW in response to oxidative stress. The current findings show that OmpW contributed to survival of planktonic cells under oxidative stress and the deletion of OmpW facilitated the biofilm formation in C. sakazakii to adapt to oxidative stress.