AUTHOR=Su Wenxiao , Deng Yiqin , Zang Shujun , Gao Si’ao , Feng Juan 

TITLE=The global role of Lrp in Vibrio alginolyticus and its response to diverse physicochemical factors

JOURNAL=Frontiers in Marine Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.1042899

DOI=10.3389/fmars.2022.1042899

ISSN=2296-7745

ABSTRACT=<p>Leucine-responsive regulatory protein (Lrp) is an essential transcriptional regulator in prokaryotes. However, the regulatory role of <italic>lrp</italic> in <italic>Vibrio alginolyticus</italic> has still not been studied in detail. In this study, an <italic>lrp</italic> mutant strain was constructed to gain insight into the role of <italic>lrp</italic> in <italic>Vibrio alginolyticus</italic>. The absence of <italic>lrp</italic> significantly enhances swarming motility, biofilm formation, extracellular protease secretion activity, and tolerance to copper ions. The cumulative mortality of zebrafish (<italic>Danio rerio</italic>) challenged by intraperitoneal injection against the <italic>lrp</italic> mutant strain reached 68.89%, significantly higher than the 40.00% suffered by fish injected with the wild-type strain. The expression levels of <italic>lrp</italic> decreased gradually with increasing culture time under the influence of various physicochemical factors. The expression level of <italic>lrp</italic> was significantly increased after two hours of culture at pH 5, 22°C, 5% NaCl, the presence of 1 mM Cu<sup>2+</sup>, 1/4/7 mM ferric citrate, 0.1 mg/L NaNO<sub>3</sub>, and 0.1 mg/L KH<sub>2</sub>PO<sub>4</sub>. The mRNA level of <italic>lrp</italic> decreased significantly after six hours of culture at 37°C, 1% and 5% NaCl, and the presence of 1/7 mM ferric citrate, 0.1/5 mg/L NaNO<sub>3</sub>, and 0.1/0.5/2.0 mg/L KH<sub>2</sub>PO<sub>4</sub>. The expression of <italic>lrp</italic> increased after ten hours of culture at pH 5/9, 22°C, 1% NaCl, and the presence of 1 mM Cu<sup>2+</sup>, 7 mM ferric citrate, 5 mg/L NaNO<sub>3</sub>, and 0.1 mg/L KH<sub>2</sub>PO<sub>4</sub>. Overall, this study indicates that <italic>lrp</italic> negatively controls the virulence of <italic>V. alginolyticus</italic>, probably by reducing its swarming motility, biofilm formation, extracellular protease secretion activity, and tolerance to copper ions, and that the expression of <italic>lrp</italic> is affected by numerous physicochemical factors, and is especially up-regulated after 2 hours of culture in bacterial growth.</p>