Growth phase-specific induction of a viable but nonculturable (VBNC) state in Listeria innocua in response to a green food sanitizer
Year: 2026
Type: article
Abstract: ABSTRACT Sustainable food sanitation and preservation technologies are highly needed to meet the increasing demand for healthy and safe food. In this work, we investigated the effects of a recently developed antimicrobial triple formulation (TF) comprised of a natural polyphenol gallic acid amended with the generally recognized as safe materials hydrogen peroxide and DL-lactic acid, on a gram-positive bacterium Listeria innocua during its exponential and stationary growth phases. Our findings revealed the physiological changes associated with the application of this material, as observed using single-cell flow cytometry, photometric assays, as well as confocal and scanning electron microscopy. Both exponential- and stationary-phase L. innocua cells lost culturability after incubation with TF, but their cellular responses were different. After 30 min of contact with the TF, the nonculturable, stationary-phase cells maintained membrane integrity, membrane potential, stable respiratory electron-transport chains, and high levels of intracellular ATP. These phenotypic features, characteristic of the viable but nonculturable (VBNC) adaptation strategy, appear to be associated with upregulation of the stress-response factor sigB . In contrast, in TF-treated exponential-phase cells, membrane integrity was severely compromised and membrane potential showed hyperpolarization, suggesting sublethal injury accompanied by downregulation of sigB . Furthermore, the TF treatment enhanced the formation of extracellular vesicles in L. innocua and the deposition of extracellular polymeric substances in stationary-phase cells. The overall findings of this work demonstrate that sensitivity of Listeria cells to nature-based antimicrobials depends on their growth phase and, therefore, modulating their growth-phase-associated physiological status may counteract their VBNC defense strategy and improve biocidal efficacy. IMPORTANCE In this work, we examined the efficacy of our novel, nature-based green sanitizer as a means to improve microbiological food safety without health and environmental risks, using gram-positive Listeria innocua as a model organism. L. innocua serves as a surrogate of the foodborne pathogen L. monocytogenes for evaluating sanitation efficacy and may also be involved in virulence and multidrug resistance transfer between the Listeria species. We demonstrate that the sanitizer effect depends on the physiological state of bacterial cells, which is affected by their growth phase. The treatment caused membrane damage to L. innocua in its exponential phase but induced the viable but nonculturable state during its stationary phase. Thus, this study demonstrates a way to overcome bacterial defense mechanisms and improve sanitizer efficacy by modulating the growth-phase-associated physiological status of targeted bacteria.
Source: Microbiology Spectrum
Authors: Esther W. Mwangi, Moshe Shemesh, Victor Rodov
Language: English
Subfield: Biotechnology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,500
OpenAlex ID: W7138411997