Propionic acid induces apoptosis‐like death in Escherichia coli O157

Abstract

Propionic acid (PPA), utilized in the manufacture of cellulose acetate propionate, is known to exhibit antimicrobial effects, but its mechanism in Escherichia coli O157 is still unknown. In general, antimicrobial activity is associated with reactive oxygen species (ROS), but ROS generation is not observed under PPA treatment. In addition to ROS, experiments were conducted to observe changes in trehalose and ion balance to discover factors that may affect the cell proliferation. Bacteria use trehalose, a sugar used for stabilization due to stress factors, which contradicts PPA concentration. Discrepancy in homeostasis follows as a result of ion imbalance. PPA causes interruption in bacterial internal stability in a dose-dependent manner.Membrane damage by ion imbalance occurs due to the binding ability of ionized PPA and divalent ions, which induce membrane depolarization, leading to a reduction in cell viability. Considering the lethal impact of membrane depolarization on cell death in bacteria, DNA fragmentation and phosphatidylserine exposure in apoptosis are confirmed. Due to severe damage in DNA, the activation of caspase-like protein is observed. Apoptosis-like death (ALD), a novel programmed cell death in bacteria, occurs eventually. In conclusion, ALD in E. coli O157 is induced via the contribution of homeostasis disruption in a ROS-independent manner.

Volatile Fatty Acids Effective as Antibacterial Agents against Three Enteric Bacteria during Mesophilic Anaerobic Incubation

“…Thus, the more concentrated they are in the growth medium, the more available they are to move into the cell; hence, the VFAs at 4 g/L were more effective against the tested bacterial strains. This agrees with Kim and Lee [17], who reported the dose-dependent nature of organic acids and also the complete inactivation of E. coli after 48 h of incubation when treated with 4 g/L of acetate, propionate and butyrate. Furthermore, the toxicity of VFAs is correlated with the pH of the growth medium (Figure S1), as also observed by Peh et al [38], because the ratio of the ionised form of VFA to the unionised form is influenced by pH.…”

“…Furthermore, Gomez-garcia et al [14] also observed that formic acid, which is also a low molecular weight VFA (C 1 ) with low pH, showed higher toxicity to Escherichia coli and Salmonella spp. Although propionic acid was comparatively the least effective VFA against all tested strains in this study, it is a potent antibacterial agent [17,50]. It achieved a significant reduction (>99%) in bacterial log CFUs at 4 g/L within the 48 h incubation period.…”

“…Enterococcus faecalis, Escherichia coli and Klebsiella pneumoniae are enteric facultative non-sporing bacteria found in the gastrointestinal tracts of humans and animals and in faecal wastes [15][16][17]. These organisms can become potentially pathogenic to humans when they find their way into soil and water environments through unsafe handling practices of human excrement and animal manure, such as the use of untreated faecal wastes as fertiliser, as these bacteria are transmissible through the faecal-oral route.…”

Weissella paramesenteroidesNRIC1542 inhibits dextran sodium sulfate‐induced colitis in mice through regulating gut microbiota and SIRT1/NF‐κB signaling pathway

“…37 At the same time, it has antibacterial effect and can induce apoptosis-like death of Escherichia coli O157 cells. 38 These evidences indicate that the final fermentation product propionic acid of Muribaculaceae is closely related to the intestinal health and immunity of the host. Moreover, Muribaculaceae has also been reported to be associated with longevity.…”

Food-Grade Bacteria Combat Pathogens by Blocking AHL-Mediated Quorum Sensing and Biofilm Formation

“…For example, lactic acid (LA), the major metabolic end-product of lactobacilli [75], has been shown to sensitize Gram-negative E. coli to antimicrobials by disrupting the outer membrane of the target cells [76] or by interrupting an AHLmediated QS system [77]. Studies on propionic acid (PA), the main metabolic end-product of propionibacteria [19], have demonstrated that this short-chain fatty acid can be used alone or in combination with different organic acids or antibiotics to potentiate antibacterial or anti-biofilm effects [78][79][80][81]. Succinic acid (SA), a key intermediate metabolite of the tricarboxylic acid cycle, is also reported with antibacterial effects, e.g., against Cutibacterium acnes or with an ability to increase the antibiotic efficacy against P. aeruginosa PAO1 and alone to induce biofilm dispersal [82][83][84][85][86].…”