Cronobacter sakazakii is a Gram-negative bacterium that causes infections in individuals of all ages, with neonates being the most vulnerable group. The objective of this study was to explore the function of the dnaK gene in C. sakazakii and to elucidate the impact of alterations in the protein composition regulated by dnaK on virulence and stress adaptation. Our research demonstrates the critical role of the dnaK gene in various key virulence factors, including adhesion, invasion, and acid resistance in C. sakazakii. Through the use of proteomic analysis, we discovered that deletion of the dnaK gene in C. sakazakii leads to an upregulation of protein abundance and increased levels of deamidated posttranscriptional modifications, suggesting that DnaK may play a role in maintaining proper protein activity by reducing protein deamidation in bacteria. These findings indicate that DnaK-mediated protein deamidation may be a novel mechanism for virulence and stress adaptation in C. sakazakii. These findings suggest that targeting DnaK could be a promising strategy for developing drugs to treat C. sakazakii infections.IMPORTANCE Cronobacter sakazakii can cause disease in individuals of all ages, with infections in premature infants being particularly deadly and resulting in bacterial meningitis and sepsis with a high mortality rate. Our study demonstrates that dnaK in Cronobacter sakazakii plays a critical role in virulence, adhesion, invasion, and acid resistance. Using proteomic analysis to compare protein changes in response to dnaK knockout, we found that dnaK knockout significantly upregulates the abundance of some proteins but also results in the deamidation of many proteins. Our research has identified a connection between molecular chaperones and protein deamidation, which suggests a potential future drug development strategy of targeting DnaK as a drug target.
Yuan Liang,Mengjun Hu,Rui Dong,Shoukui He,Yan Cui,Jinzeng Yang,Xiangyu Deng,Xianming Shi
Sodium hypochlorite (NaClO) is a widely used disinfectant in food processing environments. However, its improper use can lead Salmonella to develop tolerance to other stresses, which threatens food safety and human health. In this study, the survival ability assays showed that adaptation of S. Enteritidis to NaClO resulted in the development of heat tolerance at 55 °C and 63 °C. NaClO-adapted S. Enteritidis also showed a survival benefit in milk at 55 °C and 63 °C. NaClO-adapted S. Enteritidis exhibited a decrease in accumulation of reactive oxygen species (ROS) compared to non-adapted S. Enteritidis after exposure to 63 °C. Moreover, compared to non-adapted S. Enteritidis, the membrane fatty acids C16:0 and cyclo-heptadecanoic acid Cyc17 were significantly increased in NaClO-adapted S. Enteritidis, whereas UFA to SFA ratio was observed to decrease from 0.52 ± 0.04 to 0.41 ± 0.04. These changes resulted in a decrease in membrane fluidity of NaClO-adapted S. Enteritidis. Furthermore, RT-qPCR analysis revealed a considerable increase in the expression levels of heat shock-related genes in NaClO-adapted S . Enteritidis with or without heat treatment, in comparison to non-adapted S . Enteritidis. It was noteworthy that upregulation was 7.30-fold for dnaK , 11.62-fold for ibpA , and 3.92-fold for rpoH under heat treatment, suggesting that these genes played important roles in the development of heat tolerance. Taken together, adaptation of S . Enteritidis to NaClO resulted in the development of heat tolerance, which might increase the risk of cross-contamination and salmonellosis in the food industry.
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