Open AccessResponses of Escherichia coli and Listeria monocytogenes to ozone treatment on non-host tomato: Efficacy of intervention and evidence of induced acclimation
Author(s) -
Xiaomei Shu,
Manavi Singh,
Naga Bhushana Rao Karampudi,
David F. Bridges,
Ai Kitazumi,
Vivian C.H. Wu,
Benildo G. de los Reyes
Publication year - 2021
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0256324
Subject(s) - listeria monocytogenes , escherichia coli , transcriptome , biology , microbiology and biotechnology , downregulation and upregulation , food science , gene expression , gene , bacteria , genetics
Because of the continuous rise of foodborne illnesses caused by the consumption of raw fruits and vegetables, effective post-harvest anti-microbial strategies are necessary. The aim of this study was to evaluate the anti-microbial efficacy of ozone (O 3 ) against two common causes of fresh produce contamination, the Gram-negative Escherichia coli O157:H7 and Gram-positive Listeria monocytogenes , and to relate its effects to potential mechanisms of xenobiosis by transcriptional network modeling. The study on non-host tomato environment correlated the dose × time aspects of xenobiosis by examining the correlation between bacterial survival in terms of log-reduction and defense responses at the level of gene expression. In E . coli , low (1 μg O 3 /g of fruit) and moderate (2 μg O 3 /g of fruit) doses caused insignificant reduction in survival, while high dose (3 μg/g of fruit) caused significant reduction in survival in a time-dependent manner. In L . monocytogenes , moderate dose caused significant reduction even with short-duration exposure. Distinct responses to O 3 xenobiosis between E . coli and L . monocytogenes are likely related to differences in membrane and cytoplasmic structure and components. Transcriptome profiling by RNA-Seq showed that primary defenses in E . coli were attenuated after exposure to a low dose, while the responses at moderate dose were characterized by massive upregulation of pathogenesis and stress-related genes, which implied the activation of defense responses. More genes were downregulated during the first hour at high dose, with a large number of such genes getting significantly upregulated after 2 hr and 3 hr. This trend suggests that prolonged exposure led to potential adaptation. In contrast, massive downregulation of genes was observed in L . monocytogenes regardless of dose and exposure duration, implying a mechanism of defense distinct from that of E . coli . The nature of bacterial responses revealed by this study should guide the selection of xenobiotic agents for eliminating bacterial contamination on fresh produce without overlooking the potential risks of adaptation.