The DegU Orphan Response Regulator Contributes to Heat Stress Resistance in Listeria monocytogenes

Abstract

Listeria monocytogenes is more heat-resistant than most other non-spore-forming foodborne pathogens, posing a severe threat to food safety and human health, particularly during chilled food processing. The DegU orphan response regulator is known to control heat resistance in L. monocytogenes; however, the underlying regulatory mechanism is poorly understood. Here, we show that DegU contributes to L. monocytogenes exponential growth under mild heat-shock stress. We further demonstrate that DegU directly senses heat stress through autoregulation and upregulates the hrcA-grpE-dnaK-dnaJ operon, leading to increased production of heat-shock proteins. We also show that DegU can directly regulate the expression of the hrcA-grpE-dnaK-dnaJ operon. In conclusion, our results shed light on the regulatory mechanisms underlying how DegU directly activates the hrcA-grpE-dnaK-dnaJ operon, thereby regulating heat resistance in L. monocytogenes.

Genetic determinants of thermal resistance in foodborne bacterial pathogens

“…However, effect of the food matrix on thermal resistance is a mechanism well understood and reported (Soni et al., 2022b). It has been demonstrated that the orphan response regulator in L. monocytogenes is reported to respond to heat stress by autoregulation and upregulation of the hrcA‐grpE‐dnaK‐dnaJ operon, which in turn leads to expression of heat shock proteins (Figure 2) (Cheng et al., 2021).…”

The two-component system CpxA/CpxR is critical for full virulence in Actinobacillus pleuropneumoniae

“…Fold change data were normalized according to the housekeeping gene 16S rRNA, and analyzed using the 2 −ΔΔCt method (Livak and Schmittgen, 2001). RT-PCR acrossing the cps2A-cpxD, cpxD-cpxC, cpxC-cpxB, and cpxB-cpxA junctions was conducted as described previously (Xiong et al, 2019;Cheng et al, 2021). Amplified RT-PCR products were electrophoresed and photographed using a Gel Image Analyzing JS-1800 system (Peiqing, China).…”

“…To study the binding of CpxR to the DNA probes, the electrophoretic mobility shift assays (EMSAs) were performed using a Chemiluminescent EMSA Kit (Beyotime, Shanghai, China) as previously described (Cheng et al, 2021). The DNA probes were generated by PCR amplification from 1 to 196 bp upstream of the start codon of cpxD gene, purified using a Gel Extraction Kit (Omega, Norcross, United States), and labeled using a EMSA Probe Biotin Labeling Kit (Beyotime, Shanghai, China).…”

The CpxA/CpxR two-component system mediates regulation of Actinobacillus pleuropneumoniae cold growth

“…DNA probes were amplified and purified and then labeled using a Biotin Labeling Kit (Beyotime, China). Then, the phosphorylated CpxR and labeled probes were used for protein-DNA EMSAs as described previously (Cheng et al, 2021). Labeled DNA probe (1 μM) and various concentrations of phosphorylated CpxR protein (0-4 pmol) were incubated at 24°C for 20 min in reaction buffer (50 mM Tris-HCl, pH 8.0, 2.5 mM MgCl 2 , 100 mM KCl, 0.2 mM DTT, 10% glycerol, 2 μg salmon sperm DNA).…”