Contributions of a LysR Transcriptional Regulator to Listeria monocytogenes Virulence and Identification of Its Regulons.

The capacity of Listeria monocytogenes to adapt to environmental changes is facilitated by a large number of regulatory proteins encoded by its genome. Among these proteins are the uncharacterized LysR-type transcriptional regulators (LTTRs). LTTRs can work as positive and/or negative transcription regulators at both local and global genetic levels. Previously, our group determined by comparative genome analysis that one member of the LTTRs (NCBI accession no. WP_003734782) was present in pathogenic strains but absent from nonpathogenic strains. The goal of the present study was to assess the importance of this transcription factor in the virulence of L. monocytogenes strain F2365 and to identify its regulons. An L. monocytogenes strain lacking lysR (the F2365ΔlysR strain) displayed significant reductions in cell invasion of and adhesion to Caco-2 cells. In plaque assays, the deletion of lysR resulted in a 42.86% decrease in plaque number and a 13.48% decrease in average plaque size. Furthermore, the deletion of lysR also attenuated the virulence of L. monocytogenes in mice following oral and intraperitoneal inoculation. The analysis of transcriptomics revealed that the transcript levels of 139 genes were upregulated, while 113 genes were downregulated in the F2365ΔlysR strain compared to levels in the wild-type bacteria. lysR-repressed genes included ABC transporters, important for starch and sucrose metabolism as well as glycerolipid metabolism, flagellar assembly, quorum sensing, and glycolysis/gluconeogenesis. Conversely, lysR activated the expression of genes related to fructose and mannose metabolism, cationic antimicrobial peptide (CAMP) resistance, and beta-lactam resistance. These data suggested that lysR contributed to L. monocytogenes virulence by broad impact on multiple pathways of gene expression.IMPORTANCEListeria monocytogenes is the causative agent of listeriosis, an infectious and fatal disease of animals and humans. In this study, we have shown that lysR contributes to Listeria pathogenesis and replication in cell lines. We also highlight the importance of lysR in regulating the transcription of genes involved in different pathways that might be essential for the growth and persistence of L. monocytogenes in the host or under nutrient limitation. Better understanding L. monocytogenes pathogenesis and the role of various virulence factors is necessary for further development of prevention and control strategies.

Abdelhamed H ，Ramachandran R ，Narayanan L ，Ozdemir O ，Cooper A ，Olivier AK ，Karsi A ，Lawrence ML ... -  《-》

The VirAB ABC Transporter Is Required for VirR Regulation of Listeria monocytogenes Virulence and Resistance to Nisin.

Listeria monocytogenes is a Gram-positive intracellular pathogen that causes a severe invasive disease. Upon infecting a host cell, L. monocytogenes upregulates the transcription of numerous factors necessary for productive infection. VirR is the response regulator component of a two-component regulatory system in L. monocytogenes In this report, we have identified the putative ABC transporter encoded by genes lmo1746-lmo1747 as necessary for VirR function. We have designated lmo1746-lmo1747 virAB We constructed an in-frame deletion of virAB and determined that the ΔvirAB mutant exhibited reduced transcription of VirR-regulated genes. The ΔvirAB mutant also showed defects in in vitro plaque formation and in vivo virulence that were similar to those of a ΔvirR deletion mutant. Since VirR is important for innate resistance to antimicrobial agents, we determined the MICs of nisin and bacitracin for ΔvirAB bacteria. We found that VirAB expression was necessary for nisin resistance but was dispensable for resistance to bacitracin. This result suggested a VirAB-independent mechanism of VirR regulation in response to bacitracin. Lastly, we found that the ΔvirR and ΔvirAB mutants had no deficiency in growth in broth culture, intracellular replication, or production of the ActA surface protein, which facilitates actin-based motility and cell-to-cell spread. However, the ΔvirR and ΔvirAB mutants produced shorter actin tails during intracellular infection, which suggested that these mutants have a reduced ability to move and spread via actin-based motility. These findings have demonstrated that L. monocytogenes VirAB functions in a pathway with VirR to regulate the expression of genes necessary for virulence and resistance to antimicrobial agents.

Grubaugh D ，Regeimbal JM ，Ghosh P ，Zhou Y ，Lauer P ，Dubensky TW Jr, ，Higgins DE ... -  《-》

An insight into the role of branched-chain α-keto acid dehydrogenase (BKD) complex in branched-chain fatty acid biosynthesis and virulence of Listeria monocytogenes.

Kader Chowdhury QMM ，Islam S ，Narayanan L ，Ogunleye SC ，Wang S ，Thu D ，Freitag NE ，Lawrence ML ，Abdelhamed H ... -  《-》

Transcriptomic and phenotypic analyses identify coregulated, overlapping regulons among PrfA, CtsR, HrcA, and the alternative sigma factors sigmaB, sigmaC, sigmaH, and sigmaL in Listeria monocytogenes.

Chaturongakul S ，Raengpradub S ，Palmer ME ，Bergholz TM ，Orsi RH ，Hu Y ，Ollinger J ，Wiedmann M ，Boor KJ ... -  《-》

Role of FruR transcriptional regulator in virulence of Listeria monocytogenes and identification of its regulon.

Abdelhamed H ，Ramachandran R ，Narayanan L ，Islam S ，Ozan O ，Freitag N ，Lawrence ML ... -  《PLoS One》