High‐Intensity 405 nm Light Inactivation of <i>Listeria monocytogenes</i>

Endarko, Endarko; Maclean, Michelle; Timoshkin, I. V.; MacGregor, S.J.; Anderson, John G.

doi:10.1111/j.1751-1097.2012.01173.x

Cited by 85 publications

(67 citation statements)

References 43 publications

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“…This indicates that efficacy of LED illumination may depend on serotype and strain within the same serotype. In contrast, Endarko et al (20) reported similar sensitivities to 405-nm LED illumination among Listeria ivanovii, L. monocytogenes, and Listeria seeligeri in PBS, while the sensitivities of S. Enteritidis, S. sonnei, L. monocytogenes, and E. coli differed. Results from another study showed that treatment with a 405-nm LED in PBS caused 5-log reductions of L. monocytogenes, S. sonnei, and E. coli O157:H7 at different doses (21).…”

Section: Discussionmentioning

confidence: 84%

Antibacterial Mechanism of 405-Nanometer Light-Emitting Diode against Salmonella at Refrigeration Temperature

Kim

Yuk

2017

Appl Environ Microbiol

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The aim of this study was to elucidate the antibacterial mechanism of 405 Ϯ 5-nm light-emitting diode (LED) illumination against Salmonella at 4°C in phosphate-buffered saline (PBS) by determining endogenous coproporphyrin content, DNA oxidation, damage to membrane function, and morphological change. Gene expression levels, including of oxyR, recA, rpoS, sodA, and soxR, were also examined to understand the response of Salmonella to LED illumination. The results showed that Salmonella strains responded differently to LED illumination, revealing that S. enterica serovar Enteritidis (ATCC 13076) and S. enterica subsp. enterica serovar Saintpaul (ATCC 9712) were more susceptible and resistant, respectively, than the 16 other strains tested. There was no difference in the amounts of endogenous coproporphyrin in the two strains. Compared with that in nonilluminated cells, the DNA oxidation levels in illuminated cells increased. In illuminated cells, we observed a loss of efflux pump activity, damage to the glucose uptake system, and changes in membrane potential and integrity. Transmission electron microscopy revealed a disorganization of chromosomes and ribosomes due to LED illumination. The levels of the five genes measured in the nonilluminated and illuminated S. Saintpaul cells were upregulated in PBS at a set temperature of 4°C, indicating that increased gene expression levels might be due to a temperature shift and nutrient deficiency rather than to LED illumination. In contrast, only oxyR in S. Enteritidis cells was upregulated. Thus, different sensitivities of the two strains to LED illumination were attributed to differences in gene regulation.IMPORTANCE Bacterial inactivation using visible light has recently received attention as a safe and environmentally friendly technology, in contrast with UV light, which has detrimental effects on human health and the environment. This study was designed to understand how 405 Ϯ 5-nm light-emitting diode (LED) illumination kills Salmonella strains at refrigeration temperature. The data clearly demonstrated that the effectiveness of LED illumination on Salmonella strains depended highly on the serotype and strain. Our findings also revealed that its antibacterial mechanism was mainly attributed to DNA oxidation and a loss of membrane functions rather than membrane lipid peroxidation, which has been proposed by other researchers who studied the antibacterial effect of LED illumination by adding exogenous photosensitizers, such as chlorophyllin and hypericin. Therefore, this study suggests that the detailed antibacterial mechanisms of 405-nm LED illumination without additional photosensitizers may differ from that by exogenous photosensitizers. Furthermore, a change in stress-related gene regulation may alter the susceptibility of Salmonella cells to LED illumination at refrigeration temperature. Thus, our study provides new insights into the antibacterial mechanism of 405 Ϯ 5-nm LED illumination on Salmonella cells.

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Section: Discussionmentioning

confidence: 84%

Antibacterial Mechanism of 405-Nanometer Light-Emitting Diode against Salmonella at Refrigeration Temperature

Kim

Yuk

2017

Appl Environ Microbiol

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“…These results suggest that blue light triggers the formation of ROS and that these species have an inhibitory effect on growth, presumably because they cause oxidative damage of macromolecules in the cell (36). Previous studies have suggested the link between killing of bacteria by high-intensity visible light and ROS production (25,37). The mechanisms underlying ROS production remain to be elucidated, but endogenous porphyrins have been implicated in light inactivation studies with other bacteria (38)(39)(40).…”

Section: Discussionmentioning

confidence: 92%

“…One possible interpretation of these data was that oxygen levels in the medium were influenced by the population cell density, and that this variable might influence the sensitivity to blue light, since other studies have reported that light can lead to the generation of reactive oxygen species (ROS) (25,35). To investigate this hypothesis, we measured the inhibitory effect of blue light on cells grown in BHI medium containing the ROS scavenger dimethylthiourea (DMTU).…”

Section: Resultsmentioning

confidence: 99%

“…Visible light has been explored as an antimicrobial treatment in numerous studies, with effectiveness demonstrated against a diverse range of medically important bacteria and fungi (for reviews, see references [22][23][24]. In most cases, high-intensity violet-blue light (405 nm) has been used (25)(26)(27)(28). High-intensity light at 405 nm was found to be effective at inactivating L. monocytogenes in liquid suspensions (25) and on surfaces, including acrylic, glass, and agar-based growth medium (26,29).…”

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confidence: 99%

“…In most cases, high-intensity violet-blue light (405 nm) has been used (25)(26)(27)(28). High-intensity light at 405 nm was found to be effective at inactivating L. monocytogenes in liquid suspensions (25) and on surfaces, including acrylic, glass, and agar-based growth medium (26,29). The presence of photosensitizing compounds, such as sodium chlorophyllin (30) or 5-aminolevulinic acid (31), enhance the killing effect of visible light on surfaces.…”

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confidence: 99%

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Blue-Light Inhibition of Listeria monocytogenes Growth Is Mediated by Reactive Oxygen Species and Is Influenced by σ ^B and the Blue-Light Sensor Lmo0799

O'Donoghue

NicAogáin

Bennett

et al. 2016

Appl Environ Microbiol

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Listeria monocytogenes senses blue light via the flavin mononucleotide-containing sensory protein Lmo0799, leading to activation of the general stress response sigma factor SigB ( B ). In this study, we investigated the physiological response of this foodborne pathogen to blue light. We show that blue light (460 to 470 nm) doses of 1.5 to 2 mW cm ؊2 cause inhibition of growth on agar-based and liquid culture media. The inhibitory effects are dependent on cell density, with reduced effects evident when high cell numbers are present. The addition of 20 mM dimethylthiourea, a scavenger of reactive oxygen species, or catalase to the medium reverses the inhibitory effects of blue light, suggesting that growth inhibition is mediated by the formation of reactive oxygen species. A mutant strain lacking B (⌬sigB) was found to be less inhibited by blue light than the wild type, likely indicating the energetic cost of deploying the general stress response. When a lethal dose of light (8 mW cm ؊2 ) was applied to cells, the ⌬sigB mutant displayed a marked increase in sensitivity to light compared to the wild type. To investigate the role of the bluelight sensor Lmo0799, mutants were constructed that either had a deletion of the gene (⌬lmo0799) or alteration in a conserved cysteine residue at position 56, which is predicted to play a pivotal role in the photocycle of the protein (lmo0799 C56A). Both mutants displayed phenotypes similar to the ⌬sigB mutant in the presence of blue light, providing genetic evidence that residue 56 is critical for light sensing in L. monocytogenes. Taken together, these results demonstrate that L. monocytogenes is inhibited by blue light in a manner that depends on reactive oxygen species, and they demonstrate clear light-dependent phenotypes associated with B and the blue-light sensor Lmo0799. IMPORTANCEListeria monocytogenes is a bacterial foodborne pathogen that can cause life-threatening infections in humans. It is known to be able to sense and respond to visible light. In this study, we examine the effects of blue light on the growth and survival of this pathogen. We show that growth can be inhibited at comparatively low doses of blue light, and that at higher doses, L. monocytogenes cells are killed. We present evidence suggesting that blue light inhibits this organism by causing the production of reactive oxygen species, such as hydrogen peroxide. We help clarify the mechanism of light sensing by constructing a "blind" version of the blue-light sensor protein. Finally, we show that activation of the general stress response by light has a negative effect on growth, probably because cellular resources are diverted into protective mechanisms rather than growth.

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Hinds¹,

Bhavya²,

O’Donnell³

et al. 2021

Electromagnetic Technologies in Food Science

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High‐Intensity 405 nm Light Inactivation of Listeria monocytogenes

Cited by 85 publications

References 43 publications

Antibacterial Mechanism of 405-Nanometer Light-Emitting Diode against Salmonella at Refrigeration Temperature

Antibacterial Mechanism of 405-Nanometer Light-Emitting Diode against Salmonella at Refrigeration Temperature

Blue-Light Inhibition of Listeria monocytogenes Growth Is Mediated by Reactive Oxygen Species and Is Influenced by σ ^B and the Blue-Light Sensor Lmo0799

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High‐Intensity 405 nm Light Inactivation of Listeria monocytogenes

Cited by 85 publications

References 43 publications

Antibacterial Mechanism of 405-Nanometer Light-Emitting Diode against Salmonella at Refrigeration Temperature

Antibacterial Mechanism of 405-Nanometer Light-Emitting Diode against Salmonella at Refrigeration Temperature

Blue-Light Inhibition of Listeria monocytogenes Growth Is Mediated by Reactive Oxygen Species and Is Influenced by σ B and the Blue-Light Sensor Lmo0799

Visible Light

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Blue-Light Inhibition of Listeria monocytogenes Growth Is Mediated by Reactive Oxygen Species and Is Influenced by σ ^B and the Blue-Light Sensor Lmo0799