Recombinant Yersinia pseudotuberculosis serotype O:3 Universal stress protein B (uspB)

What is Yersinia pseudotuberculosis and how does it relate to other Yersinia species?

Yersinia pseudotuberculosis is a Gram-negative enteropathogen that causes gastrointestinal infections in humans and animals. It is evolutionarily significant as the direct ancestor of Yersinia pestis (the causative agent of plague), which emerged from Y. pseudotuberculosis within the last 40,000 years .

While Y. pseudotuberculosis typically causes self-limiting enteric disease that is rarely fatal, Y. pestis causes a severe, often fatal disease . The two species share high genetic similarity (96-100% identity in many virulence factors) , but Y. pseudotuberculosis has a much lower number of insertion sequences compared to Y. pestis, making it genetically more stable .

Key differences include:

• Y. pseudotuberculosis is primarily transmitted through contaminated food or water

• It possesses flagella and is motile, unlike Y. pestis

• It shares the pYV/pCD1 virulence plasmid with Y. pestis, encoding the Type III secretion system (T3SS)

• Y. pseudotuberculosis has a more heterogeneous population genetics compared to the evolutionary younger Y. pestis lineage

How does uspB expression respond to different growth conditions in Y. pseudotuberculosis?

Y. pseudotuberculosis undergoes significant transcriptional reprogramming during different growth phases and environmental conditions. While specific data on uspB expression is limited in the provided search results, universal stress proteins typically show increased expression under:

• Nutrient limitation during stationary phase

• Temperature stress (both high and low temperature)

• pH stress

• Oxidative stress

• Host-associated conditions

Research by Avican et al. (2015) identified different gene expression profiles between early infection (2 days post-infection) and persistent infection (42 days post-infection), with stress response genes being differentially regulated . During persistent infection, Y. pseudotuberculosis upregulates genes involved in adaptation to the cecal environment, including stress response genes.

To study uspB expression changes:

• qRT-PCR can be employed to measure uspB transcript levels under different conditions

• Transcriptional reporters (uspB promoter-GFP fusions) can visualize expression in real-time

• Western blotting with anti-uspB antibodies can determine protein levels

• RNA-seq analysis can position uspB expression within the global transcriptional landscape

What are the standard protocols for recombinant production of Y. pseudotuberculosis uspB?

For recombinant production of Y. pseudotuberculosis uspB, researchers typically follow these methodological steps:

Expression System Selection:

• E. coli BL21(DE3) is commonly used as an expression host due to its high efficiency and reduced protease activity

• Expression vectors containing T7 or similar strong promoters with appropriate tags (His, GST, etc.) facilitate purification

Cloning Strategy:

• PCR amplification of the uspB gene (YPK_0121 or YpsIP31758_4034) from Y. pseudotuberculosis genomic DNA

• Addition of appropriate restriction sites or using Gibson Assembly/InFusion cloning

• Ligation into expression vector with a purification tag

• Transformation into expression host

Expression Conditions:

• Culture in LB or other rich media at 37°C until OD600 reaches 0.6-0.8

• Induce with IPTG (0.1-1 mM)

• Lower temperature to 16-25°C for overnight expression to improve protein folding

• Harvest cells by centrifugation

Purification Protocol:

• Cell lysis using sonication or French press in appropriate buffer

• Clarification by centrifugation (10,000-20,000 x g for 30 min)

• Affinity chromatography using tag-specific resin

• Buffer exchange and concentration

• Storage in Tris-based buffer with 50% glycerol at -20°C or -80°C

Quality Control:

• SDS-PAGE to verify purity

• Western blot to confirm identity

• Mass spectrometry for accurate mass determination

• Functional assays to confirm activity

What methodologies are most effective for studying uspB function in Y. pseudotuberculosis pathogenesis?

To elucidate uspB function in Y. pseudotuberculosis pathogenesis, researchers should employ multiple complementary approaches:

Genetic Manipulation Techniques:

• Gene Deletion and Complementation:

  • Create uspB deletion mutants using suicide vectors (e.g., pRE112)

  • Confirm genotype by PCR and sequencing

  • Complement with wild-type uspB under native or inducible promoters

  • Compare phenotypes to determine function

• Transposon-Directed Insertion Site Sequencing (TraDIS):

  • Generate a high-density transposon library in Y. pseudotuberculosis

  • Subject the library to various stressors

  • Identify conditions where uspB mutants are underrepresented

  • This approach has successfully identified essential genes in Y. pseudotuberculosis

Protein-Level Investigations:

• Protein-Protein Interaction Studies:

  • Bacterial two-hybrid screening

  • Co-immunoprecipitation followed by mass spectrometry

  • Crosslinking studies to identify transient interactions

• Structural Biology:

  • X-ray crystallography or NMR to determine 3D structure

  • In silico modeling and docking studies

In Vitro Stress Response Assays:

• Growth Curves Under Stress:

  • Compare wild-type and ΔuspB strains under various stresses

  • Measure growth rates, survival, and morphological changes

• Transcriptional Response Analysis:

  • RNA-seq to determine global transcriptional changes in ΔuspB mutants

  • Identify pathways affected by uspB deletion

In Vivo Infection Models:

• Mouse Infection Studies:

  • Oral infection of mice with wild-type and ΔuspB Y. pseudotuberculosis

  • Monitor colonization of Peyer's patches, MLNs, liver, and spleen

  • Use competitive index assays to measure relative fitness

  • Assess persistence capabilities in long-term infection models

• Cell Culture Infection Models:

  • Macrophage survival assays

  • Dendritic cell interaction studies

  • Epithelial cell invasion assays

How does Y. pseudotuberculosis uspB contribute to bacterial stress responses and survival?

Y. pseudotuberculosis must adapt to diverse environmental stresses during its lifecycle, including temperature fluctuations, nutrient limitation, host immune responses, and oxidative stress. Universal stress proteins like uspB are believed to play key roles in these adaptive responses.

Stress Response Mechanisms:

• Temperature Adaptation:

  • Y. pseudotuberculosis transitions between environmental temperatures (~26°C) and mammalian host temperature (37°C)

  • RNA thermosensors regulate virulence gene expression during this transition

  • uspB may participate in membrane stabilization during temperature shifts

• Stationary Phase Survival:

  • uspB expression may increase during transition to stationary phase

  • This contributes to long-term survival under nutrient limitation

  • May be particularly important during environmental persistence

• Oxidative Stress Response:

  • Y. pseudotuberculosis encounters reactive oxygen species (ROS) produced by host immune cells

  • Universal stress proteins often protect against oxidative damage

  • The uspB protein may function as part of the bacterial antioxidant defense system

• Persistent Infection:

  • Y. pseudotuberculosis can establish persistent infections in the cecal lymphoid tissue

  • This requires extensive transcriptional reprogramming

  • Stress response systems are critical for adaptation to this niche

  • uspB may contribute to the bacteria's ability to persist in host tissues

Research Methods to Study uspB in Stress Responses:

How can recombinant uspB be utilized in vaccine development against Yersinia infections?

While the specific use of uspB in vaccine development hasn't been directly addressed in the search results, its potential can be evaluated based on general principles of Yersinia vaccine development strategies.

Potential Vaccine Applications of uspB:

Methodological Approaches for Vaccine Development:

• Live Attenuated Vaccine Platforms:

  • Y. pseudotuberculosis with uspB overexpression or modification could be evaluated

  • The χ10068 strain (Y. pseudotuberculosis with deletions in yopJ, yopK and chromosomal insertion of caf1 operon) has shown promise as a plague vaccine candidate

  • A single oral dose provided 70% protection against subcutaneous challenge and 90% protection against intranasal challenge with Y. pestis

• Immunological Assessment:

  • Evaluate antibody responses (IgG, IgA) to uspB

  • Measure T-cell responses including IFN-γ and IL-17 production

  • Assess protection in mouse models against both Y. pseudotuberculosis and Y. pestis

• Delivery Systems:

  • Investigate different adjuvants and delivery platforms

  • Test mucosal (oral, intranasal) and parenteral routes

  • Evaluate prime-boost strategies

Challenges and Considerations:

• Confirming immunogenicity of uspB in animal models

• Determining protective efficacy against different serotypes

• Addressing potential safety concerns

• Ensuring stability of recombinant uspB vaccines

How do molecular interactions between uspB and host receptors influence Y. pseudotuberculosis pathogenesis?

Known Y. pseudotuberculosis-Host Interactions:

• CD209 (DC-SIGN) Receptor Interactions:

  • Y. pseudotuberculosis utilizes its lipopolysaccharide (LPS) core to interact with CD209 receptors on dendritic cells and macrophages

  • These interactions lead to bacterial invasion of human DCs and murine macrophages

  • This facilitates dissemination to mesenteric lymph nodes (MLNs), spleen, and liver

  • Blocking CD209 receptors reduces bacterial dissemination

• Type III Secretion System (T3SS) Interactions:

  • Y. pseudotuberculosis uses T3SS to inject Yop effectors directly into host cells

  • This system requires complex host-pathogen interactions at the cell membrane

  • YscF (needle protein) mutations can separate secretion functions from translocation functions

• Invasin-Integrin Interactions:

  • The Invasin protein of Y. pseudotuberculosis binds to β1 integrins on host cells

  • This interaction enables bacterial entry into non-phagocytic cells

  • Recent studies show Invasin can sustain long-term effects in host cells

Potential uspB-Host Interactions:

If uspB has membrane-associated functions, it might:

• Interact with host immune receptors to modulate responses

• Contribute to bacterial adhesion or invasion processes

• Mediate stress sensing in the host environment

• Protect against host antimicrobial mechanisms

Methods to Study uspB-Host Interactions:

• Pull-down Assays:

  • Use purified recombinant uspB to identify binding partners from host cell lysates

  • Mass spectrometry analysis to identify interacting proteins

• Surface Plasmon Resonance:

  • Measure binding kinetics between uspB and candidate host receptors

  • Determine affinity constants and binding specificities

• Cell-Based Assays:

  • Compare wild-type and ΔuspB mutant invasion of different host cell types

  • Test the effect of anti-uspB antibodies on bacterial-host interactions

  • Use fluorescently labeled bacteria to track internalization

• In vivo Tracking:

  • Utilize bioluminescence imaging to track bacterial dissemination in mice

  • Compare wild-type and uspB mutant strains for host colonization patterns

What are the key differences in uspB structure and function between Y. pseudotuberculosis and Y. pestis?

Sequence and Structural Comparison:

While the search results don't provide direct comparison of uspB between these species, general principles of their evolutionary relationship can guide analysis:

• Sequence Conservation:

  • The core genome of Y. pestis shows high similarity to Y. pseudotuberculosis

  • uspB likely maintains high sequence identity between the species

  • Any mutations would be significant for understanding functional divergence

• Expression Patterns:

  • Y. pestis and Y. pseudotuberculosis adapt to different host environments

  • Y. pestis cycles between flea vectors and mammalian hosts

  • Expression patterns of uspB may differ based on these distinct lifestyles

  • RNA-seq studies could identify differential expression patterns

Functional Differences:

• Stress Adaptation:

  • Y. pestis faces unique stressors in the flea gut and during transmission

  • uspB may have evolved specialized functions in Y. pestis for these environments

  • Y. pseudotuberculosis uspB may be more adapted to environmental persistence

• Growth Characteristics:

  • Y. pseudotuberculosis undergoes growth arrest during T3SS expression

  • Y. pestis has different growth dynamics in host tissues

  • uspB may contribute differently to stress-induced growth modulation

Experimental Approaches for Comparative Analysis:

• Complementation Studies:

  • Express Y. pestis uspB in Y. pseudotuberculosis uspB mutants and vice versa

  • Assess restoration of phenotypes to determine functional equivalence

• Transposon-Directed Insertion Site Sequencing (TraDIS):

  • Compare the essentiality of uspB in both species under various conditions

  • The approach has been used to compare essential genes between the species

• Structural Biology:

  • Determine and compare 3D structures of uspB from both species

  • Identify structural differences that might impact function

• Host-Pathogen Interaction Studies:

  • Compare how uspB from each species interacts with host components

  • Identify differences in immunogenicity or host response modulation

How can TraDIS methodology be applied to understand uspB function in the context of Y. pseudotuberculosis essential gene networks?

Transposon-Directed Insertion Site Sequencing (TraDIS) is a powerful technique for identifying essential genes and their importance under different conditions. This methodology can elucidate uspB function within the broader context of Y. pseudotuberculosis gene networks.

TraDIS Methodology for uspB Functional Analysis:

• Library Generation:

  • Create a high-density transposon insertion library in Y. pseudotuberculosis

  • Ensure sufficient coverage (ideally multiple insertions per gene)

  • Verify library quality by preliminary sequencing

• Conditional Screening:

  • Subject the library to various conditions relevant to uspB function:

    • Different stress conditions (oxidative, temperature, pH, nutrient limitation)

    • Host-relevant environments (macrophage infection, serum exposure)

    • In vivo conditions (mouse infection model)

• Sequencing and Analysis:

  • Extract genomic DNA from surviving bacteria

  • Amplify transposon-genome junctions

  • Sequence using next-generation sequencing platforms

  • Map insertions to the Y. pseudotuberculosis genome

  • Compare insertion patterns between conditions

• Data Interpretation:

  • Genes lacking insertions are likely essential under the tested condition

  • Genes with reduced insertion frequency have fitness costs when disrupted

  • Identify conditions where uspB disruption affects fitness

Application of TraDIS Findings:

A recent TraDIS study in Y. pseudotuberculosis and Y. pestis revealed differences in essential genes between these species . This approach can be extended to understand uspB in several ways:

• Synthetic Lethality Mapping:

  • Identify genes that become essential when uspB is absent

  • This reveals functional redundancy or compensatory pathways

• Stress Response Networks:

  • Map the entire network of genes involved in specific stress responses

  • Position uspB within these networks

• Comparative Analysis with Y. pestis:

  • Compare the essentiality of uspB and interacting partners between species

  • Identify species-specific differences in gene networks

Example Data Presentation:

Insertion index represents normalized frequency of transposon insertions (0=essential, 1=non-essential)

This comprehensive approach would reveal the specific conditions under which uspB is most important and identify the gene networks with which it interacts, providing a systems-level understanding of its function in Y. pseudotuberculosis pathophysiology.