| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4563684 | LWT - Food Science and Technology | 2016 | 10 Pages |
•PL and UV upregulated stress proteins, motility genes and transcription regulators.•UV-blocked PL downregulated motility related and cell membrane related genes.•Microbicidal effects of PL on Listeria monocytogenes are primarily due to the UV spectrum.•The visible and NIR ranges do not inflict lethal effects on L. monocytogenes.
Pulsed Light (PL) is effective for inactivation of bacteria in food and non-food systems, yet the mechanisms of inactivation are not fully understood. In this work, the response of Listeria monocytogenes to PL and continuous ultraviolet light (UV) was investigated using whole genome DNA microarray analysis. Suspensions of L. monocytogenes were treated with 3.20 J/cm2 of PL and 33 mJ/cm2 of UV, respectively, which yielded comparable levels of inactivation. In a separate experiment, cells were exposed to 3.20 J/cm2 of full spectrum PL and UV-blocked PL. Whole genome microarray analysis of L. monocytogenes was performed to identify differential gene expression after the treatments, using a 1.5 fold change cutoff and adjusted P < 0.05. Compared to untreated cells, PL and UV treated cells had higher transcription levels for 80 and respectively 39 multiple stress related proteins, motility genes, and transcriptional regulators. Exposure to UV-blocked PL resulted in 131 motility related genes and cell membrane related genes with lower transcription levels, and no genes with higher transcription levels compared to untreated cells. The data suggests that the microbicidal effects of PL were primarily due to UV, and no significant differences in gene expression between PL and UV treated cells were found.
