Nitrate Utilization Promotes Systemic Infection of Salmonella Typhimurium in Mice

Li, Wanwu; Li, Linxing; Yan, Xiaolin; Wu, Pan; Zhang, Tianli; Yu, Fan; Ma, Shuai; Wang, Xinyue; Jiang, Lingyan

doi:10.3390/ijms23137220

Cited by 8 publications

(8 citation statements)

References 42 publications

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“…Wanwu Li et al. reported the mechanism of cytoplasmic acidification through transport and use of nitrate in Salmonella typhimurium, which ultimately promotes the intracellular replication and systemic infection of Salmonella Typhimurium ( Li et al., 2022 ). In this study, we found that LF82 infection resulted in macrophages acidifying rapidly.…”

Section: Discussionmentioning

confidence: 99%

“…Nitrogen metabolism is one of the important mechanisms for bacteria to adapt to an intracellular acid environment. Nitrate utilization, which is activated by both the global regulator Fnr and the nitrate-sensing two-component system NarX/NarL in S. Typhimurium, promotes S. Typhimurium intracellular replication and systemic pathogenicity ( Li et al., 2022 ). In this study, we found that nitrogen-metabolism-related genes of LF82 were upregulated in acid conditions.…”

Section: Discussionmentioning

confidence: 99%

“…Nitrogen metabolism within a restricted niche in macrophages is key to the survival and pathogenesis of intracellular pathogens ( Borah et al., 2019 ). For instance, Salmonella Typhimurium utilizes nitrate as an electron acceptor to facilitate its growth during intestinal infection and enhance systemic virulence ( Li et al., 2022 ). Several genes have been demonstrated to be crucial for nitrate metabolism including hmpA , which encodes the flavohemoglobin protein that catalyzes the conversion of NO and O 2 to nitrate ( Stevanin et al., 2002 ); narK , the primary transporter for nitrate and nitrite ( Clegg et al., 2002 ; Jia and Cole, 2005 ; Clegg et al., 2006 ); and narXL , a two-component system responsible for sensing nitrate ( Noriega et al., 2010 ; Durand and Guillier, 2021 ).…”

Section: Introductionmentioning

confidence: 99%

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Response mechanisms to acid stress promote LF82 replication in macrophages

Yao,

Huang,

Huai

et al. 2023

Front. Cell. Infect. Microbiol.

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BackgroundAdherent–invasive E. coli (AIEC) LF82 is capable of adhering to and invading intestinal epithelial cells, as well as replicating within macrophages without inducing host cell death.MethodsWe compared the transcriptomics of LF82 at pH=7.5 and pH=5.8 by RNA-sequencing, and qRT-PCR verified differentially expressed genes (DEGs). The deletion mutants of DEGs in the treatment group (pH=5.8) compared to the control group (pH=7.5) were constructed by λ recombinant. The replication differences between the mutants and WT infected Raw 264.7 at 24 h.p.i were analyzed by combining LB solid plate count and confocal observation. NH4Cl and chloroquine diphosphate (CQ) were used for acid neutralization to study the effect of pH on the replication of LF82 in macrophages. Na2NO3 was added to RPMI 1640 to study the effect of nitrate on the replication of LF82 in macrophages. 0.3% solid LB was used for flagellar motility assay and Hela was used to study flagellar gene deletion mutants and WT adhesion and invasion ability.ResultsIn this study, we found that infection with LF82 results in acidification of macrophages. Subsequent experiments demonstrated that an intracellular acidic environment is necessary for LF82 replication. Transcriptome and phenotypic analysis showed that high expression of acid shock genes and acid fitness genes promotes LF82 replication in macrophages. Further, we found that the replication of LF82 in macrophages was increased under nitrate treatment, and nitrogen metabolism genes of LF82 were upregulated in acid treatment. The replication in macrophages of ΔnarK, ΔnarXL, ΔnarP, and Δhmp were decreased. In addition, we found that the expression of flagellar genes was downregulated in acidic pH and after LF82 invading macrophages. Motility assay shows that the movement of LF82 on an acidic semisolid agar plate was limited. Further results showed that ΔfliC and ΔfliD decreased in motility, adhesion ability, and invasion of host cells, but no significant effect on replication in macrophages was observed.ConclusionIn this study, we simulated the acidic environment in macrophages, combined with transcriptome technology, and explained from the genetic level that LF82 promotes replication by activating its acid shock and fitness system, enhancing nitrate utilization, and inhibiting flagellar function.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Response mechanisms to acid stress promote LF82 replication in macrophages

Yao,

Huang,

Huai

et al. 2023

Front. Cell. Infect. Microbiol.

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“…The ∆phoBR and ∆msbB mutant strains were constructed using the λ-Red recombinase system by replacing the target genes with a chloramphenicol or kanamycin resistance gene cassette, respectively, as described previously [50]. The S. Typhimurium WT and ∆msbB, which express green fluorescent protein (GFP), were constructed through electrotransformation, as described previously [51]. S. Typhimurium was cultured in Luria-Bertani (LB) medium at 37 • C to the stationary phase (OD 600 = 1.0, ~10 9 CFUs/mL).…”

Section: Bacterial Strainsmentioning

confidence: 99%

Phosphate (Pi) Transporter PIT1 Induces Pi Starvation in Salmonella-Containing Vacuole in HeLa Cells

Yang,

Feng,

Yan

et al. 2023

IJMS

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Salmonella enterica serovar Typhimurium (S. Typhimurium), an important foodborne pathogen, causes diarrheal illness and gastrointestinal diseases. S. Typhimurium survives and replicates in phagocytic and non-phagocytic cells for acute or chronic infections. In these cells, S. Typhimurium resides within Salmonella-containing vacuoles (SCVs), in which the phosphate (Pi) concentration is low. S. Typhimurium senses low Pi and expresses virulence factors to modify host cells. However, the mechanism by which host cells reduce the Pi concentration in SCVs is not clear. In this study, we show that through the TLR4-MyD88-NF-κB signaling pathway, S. Typhimurium upregulates PIT1, which in turn transports Pi from SCVs into the cytosol and results in Pi starvation in SCVs. Immunofluorescence and western blotting analysis reveal that after the internalization of S. Typhimurium, PIT1 is located on SCV membranes. Silencing or overexpressing PIT1 inhibits or promotes Pi starvation, Salmonella pathogenicity island-2 (SPI-2) gene expression, and replication in SCVs. The S. Typhimurium ΔmsbB mutant or silenced TLR4-MyD88-NF-κB pathway suppresses the expression of the SPI-2 genes and promotes the fusion of SCVs with lysosomes. Our results illustrate that S. Typhimurium exploits the host innate immune responses as signals to promote intracellular replication, and they provide new insights for the development of broad-spectrum therapeutics to combat bacterial infections.

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“…Li et al observed an increased nitrate level during the systemic infection of STM in mice. Nitrate utilization was shown to enhance its replication inside macrophages as it acidifies the cytoplasm of STM followed by activation of SPI-2 genes [18]. Nevertheless, the NarL regulon has been more extensively studied in Escherichia coli [19,20], but hardly in STM.…”

Section: Introductionmentioning

confidence: 99%

Role of narL gene in the pathogenesis of Salmonella Typhimurium

Mani,

Priyadarsini,

K. Channabasappa

et al. 2023

J Basic Microbiol

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Salmonella Typhimurium (STM) is a facultative anaerobe and one of the causative agents of nontyphoidal salmonellosis (NTS). Its anaerobic metabolism is enabled under the hypoxic environment that is encountered inside macrophages and the gut lumen of the host. In both of these niches, free radicals and oxidative intermediates are released by neutrophils as an inflammatory response. These chemical species further undergo reactions to produce nitrate, which is preferably taken up by STM as an electron acceptor in the absence of oxygen. NarL, the response regulator of the two‐component regulatory system NarX/L, and a transcription factor, gets activated under anaerobic nitrate‐rich conditions and upregulates the nitrate reduction during anaerobic respiration of STM. To understand the role of NarL in the pathogenesis of STM, we generated a narL‐knockout (STM:ΔnarL) as well as a narL‐complemented strain of STM. Anaerobically, the mutant displayed no growth defect but a significant attenuation in the swimming (26%) and swarming (61%) motility, and biofilm‐forming ability (73%) in vitro, while these morphotypes got rescued upon genetic complementation. We also observed a downregulation in the expression of genes associated with nitrate reduction (narG) and biofilm formation (csgA and csgD) in anaerobically grown STM:ΔnarL. As compared with wild STM, narL mutant exhibited a threefold reduction in the intracellular replication in both intestinal epithelial cells (INT‐ 407) and monocyte‐derived macrophages of poultry origin. Further, in vivo competitive assay in the liver and spleen of the murine model showed a competitive index of 0.48 ± 0.58 and 0.403668 ± 0.32, respectively, for STM:ΔnarL.

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Nitrate Utilization Promotes Systemic Infection of Salmonella Typhimurium in Mice

Cited by 8 publications

References 42 publications

Response mechanisms to acid stress promote LF82 replication in macrophages

Response mechanisms to acid stress promote LF82 replication in macrophages

Phosphate (Pi) Transporter PIT1 Induces Pi Starvation in Salmonella-Containing Vacuole in HeLa Cells

Role of narL gene in the pathogenesis of Salmonella Typhimurium

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