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Fang X, Yang Y, Guo Q, Zhang Y, Yuan M, Liang X, Liu J, Fang S, Fang C. Two-component system LiaSR negatively regulated the acid resistance and pathogenicity of Listeria monocytogenes 10403S. Food Microbiol 2024; 119:104428. [PMID: 38225058 DOI: 10.1016/j.fm.2023.104428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Revised: 11/10/2023] [Accepted: 11/17/2023] [Indexed: 01/17/2024]
Abstract
The glutamate decarboxylase (GAD) system is one of the acid-resistant systems of Listeria monocytogenes (L. monocytogenes), while the regulatory mechanism of GadT2/GadD2, which plays the major role in the GAD system for acid resistance, is not clear. The two-component system (TCS) is a signal transduction system that is also involved in regulating acid resistance in bacteria. By screening the TCSs of L. monocytogenes 10403S, we found that knocking out the TCS LisSR (encoded by lmo1021/lmo1022) led to a significant increase in the transcription and expression of the gadT2/gadD2 cluster. Subsequently, we constructed a complemental strain CΔliaSR. and a complemental strain with LiaS His157 to Ala, which was designated as CΔliaSRH157A. Survival assay, transcriptional and expression analysis and pathogenicity assay revealed that liaSR deletion significantly enhanced the acid resistance and pathogenicity of 10403S and significantly increased the gadT2/gadD2 transcription and expression. Mutating LiaS His157 to Ala significantly enhanced the acid resistance and pathogenicity of CΔliaSR and significantly increased the gadT2/gadD2 transcription and expression. The results suggest that the two-component system LiaSR mediates the acid resistance and pathogenicity in 10403S by inhibiting the gadT2/gadD2 cluster, and the key activation site of LiaS is His157. This study provides novel knowledge on the regulation of GAD system and the control of this foodborne pathogen.
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Affiliation(s)
- Xiaowei Fang
- College of Animal Science, Yangtze University, No.88, Jingmi Road, Jingzhou, 434025, China; College of Agriculture, Yangtze University, No.88, Jingmi Road, Jingzhou, 434025, China
| | - Yuying Yang
- College of Animal Science, Yangtze University, No.88, Jingmi Road, Jingzhou, 434025, China
| | - Qian Guo
- College of Animal Science, Yangtze University, No.88, Jingmi Road, Jingzhou, 434025, China
| | - Yu Zhang
- College of Animal Science, Yangtze University, No.88, Jingmi Road, Jingzhou, 434025, China
| | - Mei Yuan
- College of Animal Science, Yangtze University, No.88, Jingmi Road, Jingzhou, 434025, China
| | - Xiongyan Liang
- College of Animal Science, Yangtze University, No.88, Jingmi Road, Jingzhou, 434025, China
| | - Jing Liu
- College of Animal Science, Yangtze University, No.88, Jingmi Road, Jingzhou, 434025, China
| | - Shouguo Fang
- College of Agriculture, Yangtze University, No.88, Jingmi Road, Jingzhou, 434025, China.
| | - Chun Fang
- College of Animal Science, Yangtze University, No.88, Jingmi Road, Jingzhou, 434025, China.
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Lo HY, Long DR, Holmes EA, Penewit K, Hodgson T, Lewis JD, Waalkes A, Salipante SJ. Transposon sequencing identifies genes impacting Staphylococcus aureus invasion in a human macrophage model. Infect Immun 2023; 91:e0022823. [PMID: 37676013 PMCID: PMC10580828 DOI: 10.1128/iai.00228-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 07/13/2023] [Indexed: 09/08/2023] Open
Abstract
Staphylococcus aureus is a facultative intracellular pathogen in many host cell types, facilitating its persistence in chronic infections. The genes contributing to intracellular pathogenesis have not yet been fully enumerated. Here, we cataloged genes influencing S. aureus invasion and survival within human THP-1 derived macrophages using two laboratory strains (ATCC2913 and JE2). We developed an in vitro transposition method to produce highly saturated transposon mutant libraries in S. aureus and performed transposon insertion sequencing (Tn-Seq) to identify candidate genes with significantly altered abundance following macrophage invasion. While some significant genes were strain-specific, 108 were identified as common across both S. aureus strains, with most (n = 106) being required for optimal macrophage infection. We used CRISPR interference (CRISPRi) to functionally validate phenotypic contributions for a subset of genes. Of the 20 genes passing validation, seven had previously identified roles in S. aureus virulence, and 13 were newly implicated. Validated genes frequently evidenced strain-specific effects, yielding opposing phenotypes when knocked down in the alternative strain. Genomic analysis of de novo mutations occurring in groups (n = 237) of clonally related S. aureus isolates from the airways of chronically infected individuals with cystic fibrosis (CF) revealed significantly greater in vivo purifying selection in conditionally essential candidate genes than those not associated with macrophage invasion. This study implicates a core set of genes necessary to support macrophage invasion by S. aureus, highlights strain-specific differences in phenotypic effects of effector genes, and provides evidence for selection of candidate genes identified by Tn-Seq analyses during chronic airway infection in CF patients in vivo.
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Affiliation(s)
- Hsin-Yu Lo
- Department of Laboratory Medicine and Pathology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Dustin R. Long
- Division of Critical Care Medicine, Department of Anesthesiology and Pain Medicine, University of Washington School of Medicine, Seattle, Washington, USA
| | - Elizbeth A. Holmes
- Department of Laboratory Medicine and Pathology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Kelsi Penewit
- Department of Laboratory Medicine and Pathology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Taylor Hodgson
- Department of Laboratory Medicine and Pathology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Janessa D. Lewis
- Department of Laboratory Medicine and Pathology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Adam Waalkes
- Department of Laboratory Medicine and Pathology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Stephen J. Salipante
- Department of Laboratory Medicine and Pathology, University of Washington School of Medicine, Seattle, Washington, USA
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Structural and biochemical analyses of the flagellar expression regulator DegU from Listeria monocytogenes. Sci Rep 2022; 12:10856. [PMID: 35798759 PMCID: PMC9263151 DOI: 10.1038/s41598-022-14459-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Accepted: 06/07/2022] [Indexed: 11/24/2022] Open
Abstract
Listeria monocytogenes is a pathogenic bacterium that produces flagella, the locomotory organelles, in a temperature-dependent manner. At 37 °C inside humans, L. monocytogenes employs MogR to repress the expression of flagellar proteins, thereby preventing the production of flagella. However, in the low-temperature environment outside of the host, the antirepressor GmaR inactivates MogR, allowing flagellar formation. Additionally, DegU is necessary for flagellar expression at low temperatures. DegU transcriptionally activates the expression of GmaR and flagellar proteins by binding the operator DNA in the fliN-gmaR promoter as a response regulator of a two-component regulatory system. To determine the DegU-mediated regulation mechanism, we performed structural and biochemical analyses on the recognition of operator DNA by DegU. The DegU-DNA interaction is primarily mediated by a C-terminal DNA-binding domain (DBD) and can be fortified by an N-terminal receiver domain (RD). The DegU DBD adopts a tetrahelical helix-turn-helix structure and assembles into a dimer. The DegU DBD dimer recognizes the operator DNA using a positive patch. Unexpectedly, unlike typical response regulators, DegU interacts with operator DNA in both unphosphorylated and phosphorylated states with similar binding affinities. Therefore, we conclude that DegU is a noncanonical response regulator that is constitutively active irrespective of phosphorylation.
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