title: Listeria monocytogenes MerR-Like Regulator NmlRlm: Its Transcriptome and Role in Stress Response.
abstract: NmlR, a negative transcription regulator in the MerR family, is involved in oxidative and nitrosative stress response in Neisseria gonorrhoeae and Haemophilus influenzae. In this study, the objective was to characterize the role and the regulon of NmlR in the foodborne Listeria monocytogenes. An L. monocytogenes nmlR null mutant strain was constructed. Transcriptomes of strain 10403S wild type (WT) and ΔnmlRlm strains grown to the stationary phase were determined by mRNA sequencing. Differential expression analyses revealed 74 genes with altered expression levels (>9-fold difference), comprising 46 negatively and 28 positively regulated genes. Twenty-four NmlRlm-dependent genes overlap with the members of previously identified regulons of HrcA, a negative regulator of heat response in L. monocytogenes, and of alternative sigma factor σ(H). Phenotypic characterization revealed that the ΔnmlRlm strain survived significantly less than the WT under acid stress (pH 2.5 for 1 h) and oxidative stress (3% hydrogen peroxide for 1 h). In addition, nmlRlm deletion also resulted in a significant decrease (p < 0.0005) of cell length and enhanced intracellular growth in a differentiated macrophage-like U937 cell line during entry into stationary phase. These findings indicate that NmlRlm is not only involved in oxidative stress response but also contributes to other characteristics such as acid tolerance and intracellular growth, either through direct regulation or co-regulation with other regulators such as HrcA and σ(H).
authors.affiliation: 1 Faculty of Science, Department of Microbiology, Mahidol University , Bangkok, Thailand .
authors.forename: Sirirak
authors.initials: S
authors.lastname: Supa-Amornkul
authors.affiliation: 2 Virology Laboratory, Faculty of Medicine, Department of Pathology, Ramathibodi Hospital, Mahidol University , Bangkok, Thailand .
authors.forename: Wasun
authors.initials: W
authors.lastname: Chantratita
authors.affiliation: 3 Faculty of Science, Center for Emerging Bacterial Infections, Mahidol University , Bangkok, Thailand .
authors.forename: Chutatip
authors.initials: C
authors.lastname: Srichunrusami
authors.affiliation: 2 Virology Laboratory, Faculty of Medicine, Department of Pathology, Ramathibodi Hospital, Mahidol University , Bangkok, Thailand .
authors.forename: Pareena
authors.initials: P
authors.lastname: Janchompoo
authors.affiliation: 1 Faculty of Science, Department of Microbiology, Mahidol University , Bangkok, Thailand .|3 Faculty of Science, Center for Emerging Bacterial Infections, Mahidol University , Bangkok, Thailand .
authors.forename: Soraya
authors.initials: S
authors.lastname: Chaturongakul
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008089:Listeria monocytogenes / Q000235:genetics* / Q000254:growth & development*; D018384:Oxidative Stress; D018085:Regulon; D012808:Sigma Factor / Q000235:genetics*; D059467:Transcriptome; D020298:U937 Cells
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C051124:MerR protein, Bacteria; D012808:Sigma Factor