AUTHOR=Tague Jessica G. , Regmi Abish , Gregory Gwendolyn J. , Boyd E. Fidelma 

TITLE=Fis Connects Two Sensory Pathways, Quorum Sensing and Surface Sensing, to Control Motility in Vibrio parahaemolyticus

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.669447

DOI=10.3389/fmicb.2021.669447

ISSN=1664-302X

ABSTRACT=<p>Factor for inversion stimulation (Fis) is a global regulator that is highly expressed during exponential phase growth and undetectable in stationary phase growth. Quorum sensing (QS) is a global regulatory mechanism that controls gene expression in response to changes in cell density and growth phase. In <italic>Vibrio parahaemolyticus</italic>, a marine species and a significant human pathogen, the QS regulatory sRNAs, Qrr1 to Qrr5, are expressed during exponential growth and negatively regulate the high cell density QS master regulator OpaR. OpaR is a positive regulator of capsule polysaccharide (CPS) formation, which is required for biofilm formation, and is a repressor of lateral flagella required for swarming motility. In <italic>V. parahaemolyticus</italic>, we show that Fis is a positive regulator of the <italic>qrr</italic> sRNAs expression. In an in-frame <italic>fis</italic> deletion mutant, <italic>qrr</italic> expression was repressed and <italic>opaR</italic> expression was induced. The Δ<italic>fis</italic> mutant produced CPS and biofilm, but swarming motility was abolished. Also, the <italic>fis</italic> deletion mutant was more sensitive to polymyxin B. Swarming motility requires expression of both the surface sensing <italic>scrABC</italic> operon and lateral flagella <italic>laf</italic> operon. Our data showed that in the Δ<italic>fis</italic> mutant both <italic>laf</italic> and <italic>scrABC</italic> genes were repressed. Fis controlled swarming motility indirectly through the QS pathway and directly through the surface sensing pathway. To determine the effects of Fis on cellular metabolism, we performed <italic>in vitro</italic> growth competition assays, and found that Δ<italic>fis</italic> was outcompeted by wild type in minimal media supplemented with intestinal mucus as a sole nutrient source. The data showed that Fis positively modulated mucus components L-arabinose, D-gluconate and N-acetyl-D-glucosamine catabolism gene expression. In an <italic>in vivo</italic> colonization competition assay, Δ<italic>fis</italic> was outcompeted by wild type, indicating Fis is required for fitness. Overall, these data demonstrate a global regulatory role for Fis in <italic>V. parahaemolyticus</italic> that includes QS, motility, and metabolism.</p>