AUTHOR=Patange Apurva , O’Byrne Conor , Boehm Daniela , Cullen P. J. , Keener Kevin , Bourke Paula 

TITLE=The Effect of Atmospheric Cold Plasma on Bacterial Stress Responses and Virulence Using Listeria monocytogenes Knockout Mutants

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02841

DOI=10.3389/fmicb.2019.02841

ISSN=1664-302X

ABSTRACT=<p><italic>Listeria monocytogenes</italic> is an opportunistic intracellular pathogen commonly associated with serious infections and multiple food-borne outbreaks. In this study, we investigated the influence of atmospheric cold plasma (80 kV, 50 Hz) on <italic>L. monocytogenes</italic> (EGD-e) and its knockout mutants of <italic>sigB</italic>, <italic>rsbR</italic>, <italic>prfA</italic>, <italic>gadD</italic>, and <italic>lmo0799</italic> genes at different treatment time intervals. Further, to ascertain if sub-lethal environmental stress conditions could influence <italic>L. monocytogenes</italic> survival and growth responses, atmospheric cold plasma (ACP) resistance was evaluated for the cultures exposed to cold (4°C) or acid (pH 4) stress for 1 h. The results demonstrate that both wild-type and knockout mutants were similarly affected after 1 min exposure to ACP (<italic>p</italic> &gt; 0.05), with a difference in response noted only after 3 min of treatment. While all <italic>L. monocytogenes</italic> strains exposed to acid/cold stress were hypersensitive to ACP treatment and were significantly reduced or inactivated within 1 min of treatment (<italic>p</italic> &lt; 0.05). The results indicate <italic>sigB</italic> and <italic>prfA</italic> are important for general stress resistance and biofilm, respectively, loss of these two genes significantly reduced bacterial resistance to ACP treatment. In addition, exposure to sub-lethal 1min ACP increased the gene expression of stress associated genes. <italic>SigB</italic> showed the highest gene expression, increasing by 15.60 fold, followed by <italic>gadD2</italic> (7.19) and <italic>lmo0799</italic> (8.6) after 1 min exposure. Overall, an increase in gene expression was seen in all stress associated genes analyzed both at 1 min treatment; while long treatment time reduced the gene expression and some cases down-regulated <italic>prfA</italic> and <italic>gadD3</italic> gene expression. By comparing the response of mutants under ACP exposure to key processing parameters, the experimental results presented here provide a baseline for understanding the bacterial genetic response and resistance to cold plasma stress and offers promising insights for optimizing ACP applications.</p>