Recombinant Salmonella typhimurium Spermidine export protein MdtJ (mdtJ)

What is the MdtJ protein and what is its function in bacterial cells?

MdtJ is a spermidine excretion protein that belongs to the small multidrug resistance (SMR) family of drug exporters. In bacterial cells, MdtJ functions as part of the MdtJI complex, which catalyzes the excretion of spermidine from cells . This protein plays a crucial role in polyamine homeostasis by preventing the toxic accumulation of spermidine within bacterial cells. The MdtJI complex helps bacteria recover from toxicity caused by overaccumulated spermidine, which can otherwise inhibit cell growth and potentially lead to cell death . Studies have demonstrated that when bacterial cells are exposed to elevated spermidine concentrations, the MdtJI complex enhances spermidine excretion, thereby maintaining intracellular polyamine balance and cellular health.

The functional importance of MdtJ is underscored by its conservation across various bacterial species, particularly within the Enterobacteriaceae family. Moreover, its role in spermidine export represents an important aspect of bacterial stress response mechanisms, as polyamine homeostasis is critical for normal cellular functions including DNA stability, translation accuracy, and membrane integrity.

How do MdtJ and MdtI interact to form a functional spermidine export complex?

The MdtJI complex requires both MdtJ and MdtI proteins to function effectively as a spermidine exporter. Research has shown that both mdtJ and mdtI are necessary for recovery from the toxicity of overaccumulated spermidine . The proteins likely form a heterodimeric or hetero-oligomeric complex in the bacterial membrane that creates a channel or pore through which spermidine can be transported out of the cell.

Key amino acid residues in both proteins contribute to the functionality of this complex. In MdtJ, residues Tyr4, Trp5, Glu15, Tyr45, Tyr61, and Glu82 are critical for spermidine excretion activity . Similarly, in MdtI, residues Glu5, Glu19, Asp60, Trp68, and Trp81 play important roles in the excretion activity of the MdtJI complex . These residues likely contribute to substrate recognition, binding, or the formation of the transport channel necessary for spermidine excretion.

The complementary nature of these proteins suggests a coordinated function where both components contribute specific structural and functional elements necessary for the transport mechanism. This interdependence explains why both proteins must be present for effective spermidine export and cellular protection against polyamine toxicity.

What regulatory mechanisms control mdtJ expression in response to spermidine levels?

Studies have demonstrated that mdtJI mRNA levels increase in response to elevated spermidine concentrations . This upregulation represents a feedback mechanism where the expression of the spermidine export system increases when spermidine levels rise, helping to maintain polyamine homeostasis within the cell. When bacterial cells are cultured in the presence of high spermidine concentrations (e.g., 2 mM), the MdtJI complex enhances the excretion of spermidine from cells, thereby reducing intracellular spermidine content .

The regulatory mechanisms likely involve transcriptional control elements that sense intracellular spermidine levels or their effects on cellular physiology. While the specific transcription factors and regulatory proteins involved in mdtJ regulation have not been fully characterized, this spermidine-responsive expression pattern suggests the presence of polyamine-sensitive regulatory elements in the promoter region of the mdtJI operon.

This regulatory response represents an adaptive mechanism that allows bacteria to maintain polyamine homeostasis under changing environmental conditions. Understanding these regulatory mechanisms could provide insights into bacterial stress responses and adaptation strategies.

How do recombinant Salmonella typhimurium strains interact with host cells?

Recombinant S. typhimurium strains can infect non-phagocytic cells, such as Chinese hamster ovary (CHO) cells . Once inside these cells, the bacteria can replicate intracellularly. Interestingly, when S. typhimurium bacteria are within non-phagocytic cells, they appear to be resistant to recognition by antigen-specific, major histocompatibility complex class I-restricted cytotoxic T lymphocytes (CTL) . This suggests that Salmonella may have evolved mechanisms to evade immune detection once they have entered non-phagocytic host cells.

In contrast to this immune evasion within non-phagocytic cells, mice infected with recombinant S. typhimurium that expressed fragments of influenza virus nucleoprotein (NP) in the periplasm were primed for NP-specific CTL responses . This indicates that while the bacteria may be protected from CTL attack once inside non-phagocytic cells, they can still stimulate CTL responses during infection.

These interactions between recombinant S. typhimurium and host cells have important implications for understanding pathogenesis and for developing Salmonella-based vaccine vectors. The ability of these bacteria to both stimulate immune responses and evade certain immune mechanisms represents a complex host-pathogen relationship that continues to be an active area of research.

What are the most effective approaches for generating recombinant Salmonella typhimurium strains expressing mdtJ?

When creating recombinant S. typhimurium strains expressing mdtJ, researchers should consider several methodological approaches to ensure optimal expression and functionality:

• Genetic construct design:

  • Incorporate the native promoter region to maintain natural regulation

  • Include both mdtJ and mdtI genes to ensure formation of functional complex

  • Consider codon optimization for efficient expression in S. typhimurium

  • Add epitope tags (His, FLAG, etc.) for detection, while confirming they don't interfere with function

• Expression system selection:

  • Plasmid-based expression: Utilize vectors like pUC or pMW that have been successfully used for mdtJ/mdtI expression

  • Chromosomal integration: For stable expression without antibiotic selection pressure, techniques like Tn7 transposon-mediated integration can be employed

  • Inducible promoters: Consider arabinose or tetracycline-inducible systems for controlled expression

• Transformation and selection methods:

  • Electroporation: Typically most efficient for S. typhimurium transformation

  • Triparental conjugation: Effective method as demonstrated for introducing genetic material into S. typhimurium

  • Selection markers: Use streptomycin and kanamycin resistance for effective screening

• Validation protocols:

  • RT-PCR and qPCR to confirm transcription levels

  • Western blotting with specific antibodies to validate protein expression

  • Functional assays measuring spermidine export capability

  • Growth assays in high-spermidine media to confirm protective function

These approaches provide a comprehensive framework for generating recombinant S. typhimurium strains with functional MdtJ expression, enabling further research into its role in spermidine export and bacterial physiology.

How can researchers assess the spermidine export function of MdtJ in recombinant Salmonella typhimurium?

To evaluate MdtJ-mediated spermidine export function in recombinant S. typhimurium, researchers can employ these methodological approaches:

• Spermidine toxicity assays:

  • Expose bacteria to increasing concentrations of spermidine (0.5-10 mM range)

  • Measure growth inhibition by monitoring optical density (600 nm) over 24-48 hours

  • Compare wild-type, mdtJ-knockout, and mdtJ-overexpressing strains

  • Calculate IC50 values to quantify differences in spermidine sensitivity

  • Perform time-kill assays at fixed spermidine concentrations

• Direct measurement of spermidine transport:

  • Use radiolabeled spermidine (14C or 3H) to track export kinetics

  • Measure intracellular vs. extracellular spermidine concentrations by HPLC or LC-MS/MS

  • Calculate transport rates and compare between different strains or conditions

  • Perform competition assays with other polyamines to assess specificity

• Gene expression analysis:

  • Monitor mdtJI mRNA levels in response to spermidine using qRT-PCR

  • Assess promoter activity using reporter gene constructs (e.g., luciferase or GFP)

  • Perform RNA-seq to identify co-regulated genes in the polyamine stress response

• Mutagenesis studies:

  • Create site-directed mutants targeting the key residues identified in MdtJ (Tyr4, Trp5, Glu15, Tyr45, Tyr61, and Glu82)

  • Evaluate how mutations affect spermidine export function using the assays described above

  • Correlate structure with function through complementation assays

These methods provide a comprehensive approach to characterizing the spermidine export function of MdtJ in recombinant S. typhimurium, enabling detailed understanding of its biochemical properties and physiological significance.

What strategies can be used to study the immunological response to recombinant Salmonella typhimurium expressing mdtJ?

To investigate immune responses to recombinant S. typhimurium expressing mdtJ, researchers should consider these methodological approaches:

• Animal model studies:

  • Use appropriate mouse models (e.g., C57BL/6J) for in vivo infection studies

  • Compare different infection routes: oral gavage, intraperitoneal, or intravenous administration

  • Track bacterial dissemination across tissues using barcoded strains

  • Measure immune cell recruitment and activation in infected tissues using flow cytometry

  • Assess bacterial clearance kinetics to evaluate protective responses

• Cytotoxic T lymphocyte (CTL) assays:

  • Generate antigen-specific CTL by immunizing mice with recombinant S. typhimurium

  • Isolate CTL and test their ability to recognize and kill infected target cells

  • Compare CTL responses against bacteria in different cellular compartments

  • Transfect appropriate MHC restriction molecules (e.g., HLA-B27 or H-2 Db) into target cells

• Humoral immunity assessment:

  • Measure antibody responses against MdtJ and other Salmonella antigens using ELISA

  • Determine antibody isotypes to characterize the type of immune response

  • Evaluate antibody functionality through opsonization and neutralization assays

  • Assess memory B cell development for long-term protection

• Cytokine profiling:

  • Measure pro-inflammatory and anti-inflammatory cytokine production using multiplex assays

  • Use flow cytometry to assess intracellular cytokine production in various immune cells

  • Correlate cytokine profiles with bacterial burden and disease severity

  • Compare responses between wild-type and mdtJ-deficient strains

These approaches provide a comprehensive framework for studying how the immune system recognizes and responds to recombinant S. typhimurium expressing mdtJ, offering insights into host-pathogen interactions and potential vaccine applications.

How can researchers track the in vivo dynamics of recombinant Salmonella typhimurium expressing mdtJ?

For tracking in vivo dynamics of recombinant S. typhimurium expressing mdtJ, researchers can employ these sophisticated methodological approaches:

• Genetic barcoding technology:

  • Create a library of barcoded S. typhimurium strains expressing mdtJ using Tn7 transposon-mediated integration

  • The library should contain >50,000 unique barcodes for high-resolution tracking

  • Use Illumina sequencing to identify and quantify barcode frequencies across tissues

  • Apply STAMPR (Sequence Tag-based Analysis of Microbial Populations in R) framework to analyze population dynamics

  • Calculate founding population sizes to quantify bottlenecks during infection

• In vivo imaging techniques:

  • Engineer strains to express bioluminescent (lux) or fluorescent (GFP) reporters alongside mdtJ

  • Track bacterial dissemination in real-time using whole-animal imaging

  • Perform ex vivo imaging of harvested organs for higher resolution analysis

  • Correlate signal intensity with bacterial load determined by traditional plating methods

• Quantitative tissue analysis:

  • Sample multiple organs (GI tract, liver, spleen, MLN, etc.) at various timepoints

  • Determine bacterial load by plating for CFU counts

  • Use genetic distance calculations to assess population similarity between organs

  • Identify dissemination patterns and potential reseeding events during infection

• Single-cell approaches:

  • Employ flow cytometry to isolate infected host cells from tissues

  • Use fluorescence-activated cell sorting (FACS) to separate subpopulations

  • Apply single-cell RNA-seq to characterize host-pathogen interactions at cellular level

  • Develop spatial transcriptomics methods to map infection dynamics within tissue architecture

These advanced approaches enable high-resolution tracking of bacterial population dynamics during infection, revealing patterns of dissemination, bottlenecks, and potential reseeding events that provide insights into pathogenesis and host-pathogen interactions.

What are the experimental approaches to study potential contradictions in mdtJ research findings?

When facing contradictory results in mdtJ research, researchers should employ these methodological approaches to resolve discrepancies:

How should researchers design site-directed mutagenesis experiments to study mdtJ function?

For effective site-directed mutagenesis studies of mdtJ function, researchers should implement this methodological framework:

• Target selection strategy:

  • Prioritize the known functional residues: Tyr4, Trp5, Glu15, Tyr45, Tyr61, and Glu82 in MdtJ

  • Include additional conserved residues identified through sequence alignment

  • Design mutations that test specific hypotheses about structure-function relationships

  • Create a comprehensive mutation panel as outlined in Table 1

Table 1: Key Amino Acid Residues in MdtJ and Mutation Strategy

• Mutagenesis protocol optimization:

  • Use PCR-based site-directed mutagenesis with high-fidelity polymerases to minimize errors

  • Verify all mutations by sequencing the entire mdtJ gene to confirm target changes

  • Create individual mutants as well as combinatorial mutations to assess synergistic effects

  • Maintain identical genetic backgrounds across all mutant constructs for valid comparisons

• Functional characterization framework:

  • Express mutant proteins in an mdtJ-knockout background to eliminate wild-type interference

  • Verify protein expression levels using Western blotting with antibodies against epitope tags

  • Assess membrane localization using fractionation techniques or fluorescent protein fusions

  • Measure spermidine export function through growth curves in high-spermidine conditions and direct transport assays

• Structure-function analysis:

  • Correlate mutagenesis results with predicted structural models of MdtJ

  • Consider protein-protein interactions between MdtJ and MdtI

  • Assess effects on complex formation using protein interaction assays

  • Use homology modeling based on related transporters to interpret results

This comprehensive approach will yield detailed insights into the structure-function relationships of MdtJ and its role in spermidine export, advancing our understanding of this important transport system.

What controls should be included in experiments studying recombinant Salmonella typhimurium expressing mdtJ?

A robust experimental design for studying recombinant S. typhimurium expressing mdtJ should include these essential controls:

• Genetic controls:

  • Wild-type S. typhimurium strain (positive control for natural behavior)

  • mdtJ knockout strain (negative control for mdtJ-specific effects)

  • Complemented mdtJ knockout (rescue control to confirm phenotype specificity)

  • Empty vector control (to account for vector-related effects in plasmid-based systems)

  • Inactive mutant control (expressing mdtJ with mutations in key residues like Glu15)

• Expression controls:

  • Constitutive reporter strain (to normalize for expression variations)

  • Inducible expression system (to assess dose-dependent effects)

  • qRT-PCR measurements (to confirm transcript levels across experimental conditions)

  • Western blot analysis (to verify protein expression and quantify levels)

  • Subcellular fractionation (to confirm proper membrane localization)

• Experimental condition controls:

  • Growth media without spermidine (baseline control)

  • Varying spermidine concentrations (dose-response assessment from 0.5-10 mM)

  • Alternative polyamines like putrescine or cadaverine (specificity control)

  • Temperature variations (to assess environmental effects on transport)

  • Different growth phases (log, stationary) to assess phase-dependent effects

• In vivo controls:

  • Age and sex-matched animals for infection studies

  • Sham-treated animals (receiving vehicle without bacteria)

  • Heat-killed bacterial control (to distinguish between active infection and bacterial components)

  • Single-strain infections (as references for competition experiments)

  • Tissue sampling controls (to account for sampling variability)

What are the optimal methods for measuring spermidine levels in experiments with recombinant Salmonella typhimurium?

For accurate measurement of spermidine levels in experiments with recombinant S. typhimurium, researchers should consider these methodological approaches:

• Sample preparation protocols:

  • Bacterial culture harvesting at standardized OD600 values (typically mid-log phase)

  • Quick filtration to separate cells from media without centrifugation stress

  • Immediate quenching in cold methanol (-40°C) to halt metabolism

  • Cell lysis by sonication or bead-beating in acidic conditions (pH 4.5-5.0)

  • Sample derivatization with dansyl chloride, benzoyl chloride, or o-phthalaldehyde to enhance detection sensitivity

• Analytical methods by application:

  • HPLC with fluorescence detection:

    • Sensitivity: 10-50 pmol with appropriate derivatization

    • Protocol: Reverse-phase separation using C18 column with gradient elution (acetonitrile/water)

    • Detection: Excitation/emission wavelengths optimized for the chosen derivatization reagent

    • Advantages: Widely available equipment, good reproducibility, relatively low cost

  • LC-MS/MS:

    • Sensitivity: 0.1-1 pmol, allowing detection of low abundance polyamines

    • Protocol: Multiple reaction monitoring for specific mass transitions of spermidine

    • Detection: Positive ion mode with multiple reaction monitoring (MRM)

    • Advantages: Higher specificity, ability to distinguish isotopically labeled compounds

• Data analysis considerations:

  • Standard curve preparation using purified spermidine (0.1-100 μM range)

  • Internal standards (e.g., 1,7-diaminoheptane) for normalization

  • Normalization to total protein content or cell number

  • Calculation of intracellular concentrations accounting for bacterial cell volume

• Comparative measurements:

  • Intracellular vs. extracellular spermidine measurements to assess export activity

  • Time-course analysis to determine export kinetics

  • Comparison between wild-type, mdtJ knockout, and complemented strains

  • Assessment of changes in response to environmental conditions

This comprehensive approach ensures accurate and reliable measurement of spermidine levels in experimental systems studying mdtJ function in recombinant S. typhimurium, providing crucial data for understanding polyamine transport and homeostasis.

How should researchers interpret changes in mdtJ expression levels in different experimental conditions?

For rigorous interpretation of mdtJ expression changes across experimental conditions, researchers should follow these methodological guidelines:

• Quantification methodology:

  • Use RT-qPCR with validated reference genes (such as rpoD, gyrB, or 16S rRNA) for accurate normalization

  • Calculate relative expression using the 2^(-ΔΔCt) method with appropriate controls

  • Perform absolute quantification when comparing across multiple experiments or conditions

  • Validate expression changes using independent methods (e.g., RNA-seq, protein levels by Western blot)

• Statistical analysis framework:

  • Apply appropriate statistical tests based on data distribution (parametric vs. non-parametric)

  • Use ANOVA with post-hoc tests (Tukey's or Bonferroni) for multi-condition comparisons

  • Implement mixed-effects models when analyzing time-course data

  • Report effect sizes and confidence intervals in addition to p-values for complete interpretation

• Biological context integration:

  • Correlate mdtJ expression changes with spermidine transport rates measured in parallel experiments

  • Connect expression data with intracellular spermidine concentrations

  • Examine expression of related genes involved in polyamine metabolism

  • Consider potential co-regulation with stress response pathways

• Interpretation guidelines:

  • Distinguish between statistical significance and biological relevance

  • Consider threshold fold-changes that correlate with phenotypic effects (typically >2-fold)

  • Account for post-transcriptional regulation that may affect protein levels

  • Recognize potential confounding factors such as growth phase effects or media composition

These structured approaches enable robust interpretation of mdtJ expression changes across different experimental conditions, providing insights into the regulation of this important spermidine exporter and its physiological significance in varying environments.

What approaches can researchers use to analyze the evolutionary conservation of mdtJ across different bacterial species?

To comprehensively analyze evolutionary conservation of mdtJ across bacterial species, researchers should implement this methodological framework:

• Sequence retrieval and alignment protocol:

  • Obtain mdtJ sequences from diverse bacterial genomes using BLAST searches against genomic databases

  • Perform multiple sequence alignment using MUSCLE or MAFFT for protein sequences

  • Manually curate alignments to ensure correct start site identification and proper alignment of functional domains

  • Create a dataset representing diverse bacterial taxa, with particular focus on enteric bacteria

• Phylogenetic analysis methods:

  • Construct phylogenetic trees using maximum likelihood methods (RAxML, IQ-TREE)

  • Test multiple evolutionary models and select the best-fit model using AIC or BIC criteria

  • Assess node support through bootstrap analysis (typically 1000 replicates)

  • Compare gene trees with species trees to identify potential horizontal gene transfer events

• Conservation pattern analysis:

  • Calculate sequence identity and similarity scores across species

  • Identify universally conserved residues across all homologs

  • Map conservation onto predicted structural models

  • Pay special attention to the known functional residues (Tyr4, Trp5, Glu15, Tyr45, Tyr61, Glu82)

• Functional prediction:

  • Correlate sequence conservation with experimental functional data

  • Use comparative genomics to analyze gene neighborhood and operon structure

  • Predict functional divergence using computational approaches

  • Design experiments to test functional conservation in diverse bacterial species

This systematic approach provides insights into the evolutionary history of mdtJ, identifies conserved functional elements, and guides further experimental investigations into this important spermidine exporter across the bacterial kingdom.

How can researchers resolve contradictory findings regarding the role of mdtJ in bacterial virulence?

When confronted with contradictory findings about mdtJ's role in virulence, researchers should implement these methodological approaches:

This comprehensive approach enables resolution of contradictory findings by identifying context-dependent effects, methodological differences, and mechanistic explanations for varying virulence phenotypes associated with mdtJ function.

How might understanding mdtJ function contribute to novel antimicrobial development?

Exploring mdtJ function has significant potential for antimicrobial development through these research applications:

• Target-based drug discovery approaches:

  • Structure-based design targeting the MdtJI complex:

    • Develop small-molecule inhibitors that block the spermidine binding site

    • Design peptide mimetics that disrupt MdtJ-MdtI interaction

    • Create allosteric modulators that lock the transporter in an inactive conformation

  • Virtual screening protocol using homology models based on related transporters

  • Fragment-based screening to identify initial chemical scaffolds

  • Rational design targeting the critical residues identified in functional studies (Tyr4, Trp5, Glu15, Tyr45, Tyr61, Glu82)

• Biological significance for antimicrobial strategy:

  • MdtJI inhibition could lead to toxic spermidine accumulation within bacterial cells

  • Combined inhibition of both polyamine synthesis and export would enhance efficacy

  • Potential for synergy with existing antibiotics by disrupting bacterial stress responses

  • Anti-virulence approach may reduce selection pressure for resistance development

• Resistance mechanism considerations:

  • Anticipate potential resistance through target mutations affecting inhibitor binding

  • Consider upregulation of alternative polyamine export systems as a resistance mechanism

  • Develop strategies to counter resistance through multi-target approaches

  • Design inhibitors with high barriers to resistance development

• Experimental validation pathway:

  • Initial screening using growth inhibition assays in high-spermidine conditions

  • Target validation through direct binding and transport inhibition assays

  • Specificity assessment examining effects on other transporters and human homologs

  • In vivo evaluation using appropriate animal infection models

This strategic approach to exploring mdtJ as an antimicrobial target could lead to novel therapeutic options for treating Salmonella infections and potentially other bacterial pathogens where polyamine homeostasis is critical for survival and virulence.

What are the most promising research directions for understanding the regulation of mdtJ expression?

For advancing understanding of mdtJ expression regulation, researchers should explore these promising research directions:

• Transcriptional regulation mechanisms:

  • Promoter architecture analysis through ChIP-seq to identify transcription factor binding sites

  • Map transcription start sites using 5' RACE or RNA-seq techniques

  • Characterize promoter elements through reporter gene assays with truncated promoter constructs

  • Screen for transcription factors using DNA-affinity purification coupled with mass spectrometry

  • Investigate polyamine-responsive regulators and their mechanisms of action

• Post-transcriptional control mechanisms:

  • Measure mdtJI transcript half-life under different conditions to assess mRNA stability

  • Identify potential ribonuclease involvement in transcript degradation

  • Characterize RNA structural elements affecting stability using structure probing techniques

  • Investigate potential small RNA regulators using RNA-seq and computational prediction

  • Explore the role of RNA-binding proteins in translation control

• Environmental and metabolic integration:

  • Characterize feedback mechanisms linking spermidine export to synthesis pathways

  • Investigate cross-talk with polyamine uptake systems under varying environmental conditions

  • Map metabolic fluxes using 13C-labeled spermidine and metabolic flux analysis

  • Examine regulation during various stress conditions (oxidative, acid, osmotic stress)

  • Investigate connection to global bacterial stress response networks

• In vivo expression dynamics:

  • Track mdtJ expression during infection using reporter strains in animal models

  • Compare expression across host tissues using RNA-seq of bacteria isolated from infected tissues

  • Correlate expression with bacterial population dynamics during infection

  • Investigate host-derived signals that might influence mdtJ expression

These research directions provide a comprehensive framework for understanding the complex regulation of mdtJ expression and its integration into bacterial physiology and pathogenesis, offering potential targets for therapeutic intervention and insights into bacterial adaptation mechanisms.

What experimental approaches can assess the potential role of mdtJ in bacterial adaptation to host environments?

To investigate mdtJ's role in bacterial adaptation to host environments, researchers should implement these experimental approaches:

• In vivo expression profiling methodology:

  • Construct mdtJ promoter-GFP fusions in S. typhimurium for monitoring expression

  • Use flow cytometry to assess single-cell expression levels in bacteria recovered from tissues

  • Perform fluorescence microscopy on tissue sections to visualize expression patterns in situ

  • Implement bacterial RNA enrichment protocols from host tissues for transcriptomic analysis

  • Compare expression levels across different host niches (intestine, MLN, liver, spleen)

• Genetic dissection framework:

  • Create clean mdtJ deletion mutants using scarless genome editing techniques

  • Develop complemented strains with wild-type and mutant alleles

  • Perform mixed infections with wild-type and mdtJ mutants to calculate competitive indices

  • Use barcoded strains for high-resolution tracking of population dynamics

  • Calculate founding population sizes to quantify potential bottlenecks for mutant strains

• Host environment simulation protocol:

  • Develop tissue-specific media mimicking host conditions (pH, nutrient composition, oxygen)

  • Assess growth and survival in varying conditions representing different host niches

  • Measure polyamine content in host tissues and recreate these concentrations in vitro

  • Use cell culture models representing different host cell types (epithelial, macrophage)

  • Develop intestinal organoids to study more complex host-pathogen interactions

• Evolutionary analysis approaches:

  • Compare mdtJ sequences across host-adapted Salmonella serovars with different host ranges

  • Perform experimental evolution in animal models to identify adaptive mutations

  • Sequence evolved strains to identify potential mutations in mdtJ or regulatory elements

  • Test contribution of identified mutations to fitness using allelic exchange experiments

This comprehensive experimental framework enables detailed characterization of mdtJ's role in bacterial adaptation to diverse host environments, providing insights into host-pathogen interactions and bacterial evolution during infection.