New Insights Into the Response of Metabolome of Escherichia coli O157:H7 to Ohmic Heating

Abstract

The objective of this study was to investigate the effects of ohmic heating and water bath heating (WB) on the metabolome of Escherichia coli O157:H7 cells at the same inactivation levels. Compared to low voltage long time ohmic heating (5 V/cm, 8.50 min, LVLT) and WB (5.50 min), the high voltage short time ohmic heating (10 V/cm, 1.75 min, HVST) had much shorter heating time. Compared to the samples of control (CT), there were a total of 213 differential metabolites identified, among them, 73, 78, and 62 were presented in HVST, LVLT, and WB samples, revealing a stronger metabolomic response of E. coli cells to HVST and LVLT than WB. KEGG enrichment analysis indicated that the significantly enriched pathways were biosynthesis and metabolism of amino acids (alanine, arginine, aspartate, and glutamate, etc.), followed by aminoacyl-tRNA biosynthesis among the three treatments. This is the first metabolomic study of E. coli cells in response to ohmic heating and presents an important step toward understanding the mechanism of ohmic heating on microbial inactivation, and can serve as a theoretical basis for better application of ohmic heating in food products.

3-Hydroxybutyrate Derived from Poly-3-Hydroxybutyrate Mobilization Alleviates Protein Aggregation in Heat-Stressed Herbaspirillum seropedicae SmR1

“…Although heat-shock proteins are efficient in containing cellular damage, bacteria also increase the synthesis of protective metabolites. This metabolic rewiring occurs in heat-shocked E. coli, for example, and shows that adjustments to the concentrations of specific metabolites rapidly occur during heat shock (45,46).…”

Understanding the Interactions between Staphylococcus aureus and the Raw-Meat-Processing Environment Isolate Klebsiella oxytoca in Dual-Species Biofilms via Discovering an Altered Metabolic Profile

“…Untargeted metabolomics can maximize the chances of identifying compounds by simultaneously detecting as many metabolites as possible. Therefore, this method is more likely to unearth the biochemical pathways that have not been explored before under specific biological conditions [ 20 ]. We sought to understand the potential mechanism by which DSBs are formed, in addition to the synergistic effects between S. aureus and K. oxytoca .…”

Evaluation of structural changes and intracellular substance leakage of Escherichia coli O157:H7 induced by ohmic heating

“…The OH equipment and heating cell used are the same as described by Dai et al (). The experiment was performed according to the methods of previous studies (Tian et al ; Tian et al ). Approximately 160 ml E. coli O157:H7 suspension was assigned to the heating cell.…”

“…A homemade thermoelectric probe encased with isolative ceramic was used to record the geometry centre temperature of samples at 0·5‐ min interval. Two experimental protocols were designed as follow: (i) Both OH and WB protocols were designed to obtain the same inactivation level of E. coli O157:H7 at less than 2 log CFU per ml on tryptone soy agar (TSA), which took 1·75 min at 10 V cm −1 to reach final temperature of 57·90°C (high voltage low temperature, HVLT) and 8·50 min at 5 V cm −1 to reach a final temperature of 58·60°C (low voltage low temperature, LVLT), respectively (Tian et al ). (ii) The samples were heated to a targeted temperature of 72°C, which took 3·00 min at 10 V cm −1 (high voltage high temperature, HVHT) and 13·00 min at 5 V cm −1 (low voltage high temperature, LVHT), respectively.…”

“…In our previous studies, the cellular protein content of E. coli O157:H7 was significantly lower in two OH protocols (10 V cm −1 , 3·00 min and 5 V cm −1 , 13·00 min) than water bath heating (WB, 13·00 min) at the same heating temperature of 72°C, indicating that more cellular proteins of E. coli O157:H7 might leak out during OH (Tian et al ). In addition, the metabolites showed different changes among two OH protocols (10 V cm −1 , 1·75 min and 5 V cm −1 , 8·50 min) and WB (5·50 min) at the same inactivation level (Tian et al ). Therefore, the same heating temperature and inactivation level mentioned above are used in this study to investigate the changes in the membrane permeability, membrane structure, intracellular organization, leakage of intracellular substances and endogenous enzyme activity of E. coli O157:H7 subjected to OH and WB using flow cytometry (FCM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet spectrometer.…”