Response to Acid Adaptation in Salmonella enterica Serovar Enteritidis

Abstract

Acid adaptation in Salmonella Enteritidis was characterized by phenotypic and gene‐expression analyses. S. Enteritidis cells at log‐phase and stationary‐phase were kept at pH 4.5 to 6.0 for 1 to 4 hours. All treatments induced various levels of acid tolerance response that were dependent on pH, exposure time and growth phase. This acid adaptation resulted in tolerance to 50 °C and 8% NaCl regardless of the growth phase. However, the tolerance of log‐phase and stationary‐phase cells to low temperatures (4 and –20 °C) was increased and decreased, respectively. RT‐qPCR analysis revealed that genes involved in tolerance to acid (SEN1564A and cfa), heat (rpoH, uspB, and htrA), salt (proP, proV, and osmW), and cold (cspA, cspC, and csdA) stress were generally upregulated after acid adaptation. These results provide an initial insight into mechanisms of acid adaptation and induced cross protection in S. Enteritidis. Practical Application Stress tolerance acquisition resulting from acid adaptation in foodborne pathogens poses a great threat to food safety. The current work showed that acid adaptation induced direct tolerance and cross‐tolerance to high temperature, low temperature, and salt in Salmonella Enteritidis, possibly due to the upregulation of stress tolerance‐related genes. These results provide key insights into acid adaptation mechanisms and efficient control of S. Enteritidis.

Sublethal concentrations of undissociated acetic acid may not always stimulate acid resistance in Salmonella enterica sub. enterica serovar Enteritidis Phage Type 4: Implications of challenge substrate associated factors

“…This inorganic acid was used because it is completely dissociated in aqueous environments and therefore itself is not toxic for the cells [ 29 ]. In line with previous reports, adaptation to moderate pH values (4.0–5.5) protected cells against subsequent acid exposure, with higher resistance observed at the lower pH values (4.0 and 4.5) [ 30 – 33 ]. Nonetheless, the pH values required for the induction of acid resistance in pH adapted cells were lower compared to the milder pH values (5.5–6.0) required in the presence of acetic acid.…”

“…Shen, Yu and Chou [50] reported that whereas no differences were observed between acid adapted and non-adapted cells of S. Typhimurium inoculated in skim milk and treated fermented milk stored at 37˚C, acid adaptation, in addition to promoting acid resistance, decreased the susceptibility of the pathogen to refrigeration (5˚C). Nonetheless, it is not the first time that the effects of acid adaptation are counteracted by subsequent stressors, increasing the sensitivity of acid adapted cells to lethal stresses compared to their non-adapted counterparts [33,51,52].…”

Differences in Acid Stress Response of Lacticaseibacillus paracasei Zhang Cultured from Solid-State Fermentation and Liquid-State Fermentation

“…CspA , a gene encoding cold shock protein, was up-regulated by 7.29 times in the liquid-state fermented cells compared with the solid-state fermented cells. This gene has been reported to be involved in the response to cold stress and acid stress [ 70 ]. Gene rimP encoding ribosome maturation factor was up-regulated by 2.58 times.…”

Investigating the effects of environmental stresses on Salmonella enterica serovar Tennessee survival in a low moisture food model

“…Due to the multitude of genes involved in each stress response, it is difficult to single‐out a specific direct response. In previous experiments, it was found that exposure to one stress primes tolerance to other stresses (Stackhouse et al., 2012; Vorob'eva, 2004; Ye et al., 2019). In this study, the bacteria are exposed to either one, some, or all of the stresses.…”