Flagellar Basal Body Structural Proteins FlhB, FliM, and FliY Are Required for Flagellar-Associated Protein Expression in Listeria monocytogenes

Abstract

Listeria monocytogenes is a food-associated bacterium that is responsible for food-related illnesses worldwide. In the L. monocytogenes EGD-e genome, FlhB, FliM, and FliY (encoded by lmo0679, lmo0699, and lmo0700, respectively) are annotated as putative flagella biosynthesis factors, but their functions remain unknown. To explore whether FlhB, FliM, and FliY are involved in Listeria flagella synthesis, we constructed flhB, fliM, fliY, and other flagellar-related gene deletion mutants using a homologous recombination strategy. Then, we analyzed the motility, flagella synthesis, and protein expression of these mutant strains. Motility and flagella synthesis were completely abolished in the absence of flhB, fliM, or fliY. These impaired phenotypes were fully restored in the complemented strains CΔflhB, CΔfliM, and CΔfliY. The transcriptional levels of flagellar-related genes, including flaA, fliM, fliY, lmo0695, lmo0698, fliI, and fliS, were downregulated markedly in the absence of flhB, fliM, or fliY. Deletion of flhB resulted in the complete abolishment of FlaA expression, while it decreased FliM and FliY expression. The expression of FlaA was abolished completely in the absence of fliM or fliY. No significant changes were found in the expression of FlhF and two flagella synthesis regulatory factors, MogR and GmaR. We demonstrate for the first time that FlhB, FliM, and FliY not only mediate Listeria motility, but also are involved in regulating flagella synthesis. This study provides novel insights that increase our understanding of the roles played by FlhB, FliM, and FliY in the flagellar type III secretion system in L. monocytogenes.

Prevalence, Pathogenicity, Virulence, Antibiotic Resistance, and Phylogenetic Analysis of Biofilm-Producing Listeria monocytogenes Isolated from Different Ecological Niches in Egypt: Food, Humans, Animals, and Environment

“…Studies of the functions of flagellar-related proteins in L. monocytogenes are in the preliminary stage. Although the characteristic tumbling motility of L. monocytogenes was observed in all of our 27 isolates, the flaA gene was not detected from four of these motile isolates, stipulating that there are alternative mechanisms controlling the flagella and the secretion of other flagella-related proteins involved in the synthesis of the L. monocytogenes flagellum required for its motility and the secretion of supplementary flagellar-related proteins [60]. Attachment and formation of biofilm allows the colonization of surfaces, including food processing environments [61].…”

A Novel Small RNA Promotes Motility and Virulence of Enterohemorrhagic Escherichia coli O157:H7 in Response to Ammonium

“…Although FlhB is generally regarded as a class 2 flagellar biosynthetic protein ( 46 ), recently flhB was reported to regulate the expression of several flagellar genes, including flaA (O157 fliC homolog), fliY , fliS , motA , lmo0695 , and lmo0698 , in Listeria monocytogenes ( 17 ). Hence, we performed qRT-PCR to determine whether flhB regulates the expression of flagellar genes in O157.…”

“…Class 3 encodes components for filament assembly and motor function, including the flagellin gene, fliC . FlhB is a class 2 constituent membrane protein of the basal body required for flagellar appendant synthesis and hook-length control involved in substrate specificity switch ( 17 , 18 ). Recently, FlhB was found to regulate flagellar gene expression in Listeria monocytogenes ( 17 ).…”

Initial Transcriptomic Response and Adaption of Listeria monocytogenes to Desiccation on Food Grade Stainless Steel

“…Moreover, Lm 568 downregulated fliY (lmo0693, flagellar motor switch protein), while Lm 08-5578 downregulated the chemotaxis protein lmo1699 ( Supplementary Table S2). A study by Cheng et al (2018) showed how in the absence of either FlhB, FliM or FliY L. monocytogenes completely lost its ability to produce flagella. Downregulation of motility genes in response to desiccation have also been observed in Pseudomonas putida (Van de Mortel and Halverson, 2004) and Enterobacter sakazakii (Riedel and Lehner, 2007).…”