Recombinant Escherichia fergusonii UPF0114 protein YqhA (yqhA)

How can E. fergusonii be distinguished from E. coli in laboratory settings?

E. fergusonii is frequently misidentified as E. coli using traditional biochemical methods. For reliable identification, molecular techniques should be employed:

• Phenotypic identification: E. fergusonii produces dark yellow to orange colonies on Simmons Citrate Agar (SCA) supplemented with 2% adonitol and appears colorless on Sorbitol MacConkey Agar (SMAC). Positive reactions for cellobiose and arabinose fermentation are characteristic .

• Molecular confirmation: The recommended approach is PCR amplification targeting:

  • Palmitoleoyl-ACP-dependent acyltransferase gene (575-bp product)

  • EFER13 and EFER YP-specific primers in duplex PCR

  • 16S rRNA gene sequencing using universal primers (27F and 1492R)

• Advanced identification: To distinguish from E. coli when API 20E identification kits show inconclusive results, use primers targeting specific genes including:

  • Beta-glucuronidase enzyme

  • Conserved hypothetical cellulose synthase protein

  • Regulator of cellulose synthase

  • Putative transcriptional activator for multiple antibiotic resistance

The limitation of commercial biochemical identification systems has been demonstrated in studies where 100% of presumptive E. fergusonii isolates were misidentified as E. coli by API 20E identification kits .

What are the optimal conditions for recombinant expression of E. fergusonii UPF0114 protein YqhA?

Based on experimental design approaches for recombinant protein expression, the following methodology is recommended:

• Expression system selection: E. coli is the preferred host due to its rapid growth at high cell density, well-established genetic background, and availability of commercial cloning vectors .

• Optimization using multivariant analysis: Rather than varying one condition at a time, employ a statistical experimental design methodology (fractional factorial screening design) to assess multiple variables simultaneously:

  • Medium composition (8 variables)

  • Induction conditions

  • Expression time (4-6 hours recommended based on productivity balance)

• Key variables to optimize:

  • Temperature (lower temperatures often improve soluble protein yield)

  • IPTG concentration (for induction)

  • Cell density at induction

  • Media composition (carbon source, nitrogen source, salt concentration)

  • Expression time

  • pH

• Assessment methods:

  • Monitor cell growth (OD600)

  • Protein expression levels (SDS-PAGE)

  • Protein activity assays

  • Solubility fraction analysis

This approach allows for the efficient determination of optimal culture conditions with fewer experiments and minimal resources while maintaining statistical validity through orthogonality .

How can the solubility of recombinant E. fergusonii UPF0114 protein YqhA be enhanced during expression?

Enhancing the solubility of membrane proteins like YqhA requires specific strategies:

• Temperature optimization: Lower the expression temperature to 16-25°C after induction to slow down protein synthesis and allow proper folding.

• Media supplementation:

  • Add osmolytes such as sorbitol (0.5-1.0 M) and glycyl-glycine (0.25-0.5 M)

  • Include chaperone-inducing compounds like benzyl alcohol (5-10 mM)

  • Consider detergent supplementation for membrane proteins (0.1-0.5% non-ionic detergents)

• Genetic modifications:

  • Co-express with molecular chaperones (GroEL/GroES, DnaK/DnaJ/GrpE)

  • Use fusion tags that enhance solubility (MBP, SUMO, Thioredoxin)

  • Consider codon optimization for the host organism

• Induction strategy:

  • Use lower IPTG concentrations (0.1-0.5 mM) for slower, more controlled induction

  • Implement auto-induction systems for gradual protein expression

• Post-induction supplementation:

  • Add specific cofactors or ligands that might stabilize the protein structure

  • Consider arginine and glutamic acid (50-100 mM each) as chemical chaperones

These approaches have been shown to increase soluble protein yields from negligible amounts to up to 250 mg/L for challenging proteins .

What methods are recommended for purification and characterization of recombinant E. fergusonii UPF0114 protein YqhA?

For membrane proteins like YqhA, the following purification and characterization strategy is recommended:

• Initial extraction:

  • For membrane proteins, use appropriate detergents (DDM, LDAO, or FC-12) for solubilization

  • Optimize detergent concentrations through small-scale screening (0.5-2% range)

  • Consider alternate solubilization methods such as SMA copolymers for native-like extraction

• Purification strategy:

  • Immobilized Metal Affinity Chromatography (IMAC) using the histidine tag

  • Size Exclusion Chromatography (SEC) for further purification and assessment of homogeneity

  • Ion Exchange Chromatography as an additional polishing step if needed

• Protein characterization:

  • Confirm identity via Mass Spectrometry (MS)

  • Assess purity by SDS-PAGE and Western blotting

  • Analyze secondary structure using Circular Dichroism (CD)

  • Determine thermal stability using Differential Scanning Fluorimetry (DSF)

  • Verify membrane integration using liposome reconstitution assays

• Functional characterization:

  • Membrane localization studies using fluorescently-tagged protein

  • Interaction studies with potential binding partners

  • Assessment of ion or small molecule transport capabilities if applicable

For storage of purified protein, maintain in Tris-based buffer with 50% glycerol at -20°C or -80°C for extended storage. Avoid repeated freeze-thaw cycles and consider storing working aliquots at 4°C for up to one week .

How can researchers assess the functional integrity of recombinant E. fergusonii UPF0114 protein YqhA?

Assessing functional integrity of YqhA requires multiple complementary approaches:

• Structural integrity assessment:

  • Circular Dichroism (CD) spectroscopy to confirm proper secondary structure

  • Fluorescence spectroscopy to assess tertiary structure

  • Size-exclusion chromatography with multi-angle light scattering (SEC-MALS) to determine oligomeric state

• Membrane integration studies:

  • Reconstitution into liposomes or nanodiscs

  • Proteoliposome flotation assays to confirm membrane association

  • Fluorescence microscopy with GFP-fusion proteins to visualize cellular localization

• Functional assays based on predicted roles:

  • Membrane permeability assays using fluorescent dyes

  • Ion flux measurements if ion channel/transporter activity is suspected

  • Binding assays with potential interaction partners using techniques such as:

    • Surface Plasmon Resonance (SPR)

    • Microscale Thermophoresis (MST)

    • Isothermal Titration Calorimetry (ITC)

• In vivo complementation studies:

  • Generate knockout strains lacking yqhA

  • Assess phenotypic changes

  • Complement with recombinant protein to verify functional restoration

• Stability assessment in different conditions:

  • pH range (pH 5-9)

  • Temperature stability (4-60°C)

  • Detergent screening for optimal stability

  • Lipid composition effects on function

How does E. fergusonii UPF0114 protein YqhA compare across different bacterial species, and what are the evolutionary implications?

The UPF0114 protein family, including YqhA, is conserved across multiple bacterial species, particularly within Enterobacteriaceae. Comparative analysis reveals:

• Sequence conservation and divergence:

  • Core structural elements are highly conserved, particularly transmembrane domains

  • Greater sequence variation occurs in loop regions

  • Phylogenetic analysis indicates YqhA from E. fergusonii clusters closely with homologs from E. coli strains

• Functional conservation:

  • UPF0114 proteins likely maintain similar core functions across species

  • Species-specific adaptations may relate to environmental niches

  • Potential roles in membrane integrity, stress response, or small molecule transport

• Evolutionary trajectory:

  • UPF0114 proteins appear to have evolved from a common ancestor

  • Horizontal gene transfer evidence is minimal, suggesting vertical inheritance

  • Selective pressure analysis indicates functional constraints on transmembrane regions

• Pangenomic context:

  • YqhA belongs to the core genome of E. fergusonii (present in all strains)

  • Core genome analysis of E. fergusonii reveals approximately 2,911 non-redundant proteins

  • Comparative genomics with other Escherichia species provides context for evolutionary relationships

This evolutionary conservation suggests biological significance and may indicate roles in essential cellular processes rather than virulence-specific functions .

What role might E. fergusonii UPF0114 protein YqhA play in antimicrobial resistance, and how can this be studied?

While direct evidence of YqhA involvement in antimicrobial resistance (AMR) is limited, its membrane localization and conservation across resistant strains warrant investigation:

• Potential mechanisms for AMR involvement:

  • Membrane permeability alterations affecting antibiotic uptake

  • Interaction with efflux pump systems

  • Biofilm formation contributions

  • Stress response modulation under antibiotic pressure

• Research methodology to investigate YqhA in AMR:

  • Generate knockout and overexpression strains to assess changes in:

    • Minimum Inhibitory Concentrations (MICs) for various antibiotics

    • Expression of known resistance genes

    • Membrane permeability characteristics

    • Biofilm formation capacity

  • Transcriptomic analysis:

    • RNA-seq comparing expression in resistant vs. susceptible strains

    • qRT-PCR validation of differential expression under antibiotic stress

  • Protein interaction studies:

    • Co-immunoprecipitation to identify binding partners

    • Bacterial two-hybrid assays to screen for interactions with known AMR proteins

  • Structural studies:

    • Cryo-EM or X-ray crystallography to determine protein structure

    • In silico modeling of potential antibiotic binding sites

• Contextual relevance to E. fergusonii AMR:

  • E. fergusonii strains show high rates of resistance to multiple antibiotics:

    • 100% resistance to penicillin G

    • 77% resistance to erythromycin

    • Resistance to extended-spectrum beta-lactams and colistin

  • Avian and porcine strains carry significantly higher numbers of AMR genes and mobile genetic elements than strains from other sources

  • Plasmid replicon typing reveals IncF and IncI1 as common replicons among resistant isolates

This research could elucidate whether YqhA plays a direct role in AMR mechanisms or serves as a marker for tracking resistant strains .

What approaches can be used to develop and validate a multi-epitope vaccine targeting E. fergusonii proteins including YqhA?

Development of a multi-epitope vaccine targeting E. fergusonii proteins requires a systematic bioinformatics-based approach followed by experimental validation:

• Initial bioinformatic analysis pipeline:

  • Complete proteome retrieval of all known E. fergusonii strains from NCBI

  • Bacterial pan-genome analysis (BPGA) to identify core proteome

  • Subcellular localization prediction focusing on extracellular, outer membrane, and periplasmic proteins

  • Filtering based on:

    • Homology checks

    • Transmembrane helices assessment

    • Virulence factor database (VFDB) analysis

    • Antigenicity prediction

• Epitope prediction and selection:

  • B-cell epitope prediction using immune epitope database (IEDB)

  • T-cell epitope prediction for MHC-I and MHC-II binding

  • Filtering epitopes based on:

    • Antigenicity (≥0.4)

    • Absence of toxicity

    • Good water solubility

    • Non-allergenicity

    • Strong MHC binding efficiency

• Multi-epitope vaccine (MEV) design:

  • Construct a chimeric protein with selected epitopes

  • Include appropriate linkers between epitopes

  • Add adjuvant sequences to enhance immunogenicity

  • Evaluate using various bioinformatics tools

• In silico validation:

  • Structure prediction and refinement

  • Molecular docking with immune receptors (MHC-I, MHC-II, TLR4)

  • Molecular dynamics simulations to assess binding stability

  • In silico cloning expression prediction

• Experimental validation pathway:

  • Recombinant expression and purification

  • In vitro immunological assays:

    • Cytokine production profiles

    • Antibody response measurement

    • Cell-mediated immunity assessment

  • Animal model testing:

    • Immunogenicity

    • Protection against challenge

    • Safety profiles

This methodical approach has yielded promising results in other bacterial vaccine development efforts, with candidates showing high efficiency in experimental phases .

How could structural studies of E. fergusonii UPF0114 protein YqhA contribute to antimicrobial drug development?

Structural studies of YqhA could provide valuable insights for antimicrobial development through several mechanisms:

• Structure determination approaches:

  • X-ray crystallography of purified protein (challenging for membrane proteins)

  • Cryo-electron microscopy for structure determination in near-native states

  • NMR spectroscopy for dynamic structural information

  • Computational modeling leveraging homology with related proteins

• Structure-based drug design potential:

  • Identification of potential binding pockets that could serve as drug targets

  • Virtual screening of compound libraries against solved structures

  • Fragment-based drug design focusing on high-affinity binding sites

  • Design of peptide inhibitors targeting protein-protein interactions

• Functional insights from structure:

  • Elucidation of potential transport channels or pores

  • Identification of conformational changes related to function

  • Understanding of membrane integration and topology

  • Recognition of structural features conserved across pathogenic species

• Applications to antimicrobial development:

  • If YqhA proves essential for bacterial survival, it becomes a direct target

  • Structure-guided design of small molecule inhibitors

  • Development of peptidomimetics that disrupt protein-protein interactions

  • Creation of antibodies or nanobodies targeting accessible epitopes

• Challenges and strategies:

  • Membrane protein crystallization difficulties require specialized approaches:

    • Lipidic cubic phase crystallization

    • Fusion with crystallization chaperones

    • Nanobody-aided crystallization

  • Validation of structural models through mutagenesis and functional assays

The emerging pathogenic nature of E. fergusonii and its increasing antimicrobial resistance profile make structural studies of its proteins particularly relevant for future therapeutic development .

What experimental approaches could determine the physiological role of E. fergusonii UPF0114 protein YqhA in bacterial membrane function?

Determining the physiological role of YqhA requires a comprehensive approach combining genetic, biochemical, and biophysical techniques:

• Genetic manipulation strategies:

  • CRISPR-Cas9 or allelic exchange for gene deletion

  • Controlled expression systems (inducible promoters) for titrating protein levels

  • Site-directed mutagenesis of conserved residues

  • Complementation studies with wild-type and mutant variants

  • Construction of reporter fusions (GFP, luciferase) to study expression patterns

• Phenotypic characterization of mutants:

  • Growth curves under various stress conditions (pH, temperature, osmotic stress)

  • Membrane integrity assays using fluorescent dyes

  • Antibiotic susceptibility profiles

  • Biofilm formation capacity

  • Metabolic profiling using Biolog phenotype microarrays

• Biochemical analysis:

  • Lipidomic analysis to detect changes in membrane composition

  • Measurement of membrane potential and permeability

  • Protein-lipid interaction studies using reconstituted systems

  • Identification of interaction partners through pull-down assays and mass spectrometry

  • Assessment of ion or small molecule transport capabilities

• Advanced biophysical approaches:

  • Atomic Force Microscopy to assess membrane mechanical properties

  • Fluorescence Recovery After Photobleaching (FRAP) to study protein mobility

  • Single-molecule tracking to monitor dynamics in living cells

  • Solid-state NMR to study protein-lipid interactions in native-like environments

• Systems biology integration:

  • Transcriptomic analysis to identify co-regulated genes

  • Proteomic profiling to detect compensatory changes upon YqhA deletion

  • Metabolomic analysis to identify affected pathways

  • Computational modeling of potential functions based on integrated data

These approaches would provide comprehensive insights into YqhA's role in bacterial physiology and potentially reveal novel therapeutic targets .

How can molecular modeling and simulation methods be applied to study E. fergusonii UPF0114 protein YqhA structure-function relationships?

Computational approaches offer powerful tools for investigating membrane proteins like YqhA when experimental structural data is limited:

• Homology modeling workflow:

  • Template identification using HHpred, Phyre2, or I-TASSER

  • Sequence alignment optimization focusing on transmembrane regions

  • Model building with MODELLER or SWISS-MODEL

  • Loop refinement for connecting transmembrane segments

  • Model validation using PROCHECK, ERRAT, and QMEANBrane

• Molecular dynamics simulation approaches:

  • System preparation incorporating the protein in a lipid bilayer

  • Equilibration protocols for membrane systems (50-100 ns)

  • Production simulations (microsecond scale when possible)

  • Analysis of:

    • Protein stability and conformational changes

    • Lipid-protein interactions

    • Water and ion permeation

    • Potential binding sites identification

• Advanced simulation techniques:

  • Coarse-grained simulations for longer timescales (MARTINI force field)

  • Enhanced sampling methods:

    • Metadynamics for free energy calculations

    • Replica exchange molecular dynamics for conformational sampling

    • Steered molecular dynamics for studying mechanical properties

  • Hybrid quantum mechanics/molecular mechanics for detailed interaction studies

• Virtual screening and docking:

  • Identification of potential binding pockets

  • High-throughput virtual screening against compound libraries

  • Molecular docking of potential interaction partners

  • Binding free energy calculations

• Integration with experimental data:

  • Refinement of models based on crosslinking constraints

  • Validation using site-directed mutagenesis results

  • Comparison with low-resolution structural data

  • Development of testable hypotheses for experimental validation

These computational approaches can provide valuable insights into protein function and guide experimental efforts in a cost-effective manner .

What strategies can researchers employ when encountering difficulties in expressing soluble recombinant E. fergusonii UPF0114 protein YqhA?

When facing challenges in soluble expression of membrane proteins like YqhA, researchers can employ these troubleshooting strategies:

• Expression system optimization:

  • Try alternative E. coli strains specialized for membrane proteins:

    • C41(DE3) and C43(DE3) - Walker strains

    • Lemo21(DE3) for tunable expression

    • SHuffle for enhanced disulfide bond formation

  • Consider eukaryotic expression systems for complex membrane proteins:

    • Yeast (Pichia pastoris, Saccharomyces cerevisiae)

    • Insect cells (Sf9, Hi5)

    • Mammalian cells for post-translational modifications

• Vector and construct design improvements:

  • Optimize the signal sequence or add a suitable signal peptide

  • Try different fusion tags: SUMO, MBP, Mistic, or GST

  • Adjust the position of the purification tag (N vs. C-terminal)

  • Remove flexible regions that might interfere with folding

  • Consider expressing functional domains separately

• Expression condition modifications:

  • Implement a factorial design approach testing multiple variables:

    • Temperature (15-37°C)

    • Inducer concentration (0.01-1.0 mM IPTG)

    • Media composition (LB, TB, 2XYT, M9)

    • Additives (glycerol, sorbitol, arginine, proline)

  • Use auto-induction media for gradual protein expression

  • Test different cell densities at induction (OD600 0.4-1.2)

• Solubility enhancement strategies:

  • Co-express with molecular chaperones (GroEL/ES, DnaK/J/GrpE)

  • Add membrane-mimetic environments during extraction:

    • Detergents (DDM, LDAO, FC-12)

    • Amphipols

    • Nanodiscs

  • Include stabilizing ligands if known

• Extraction and purification optimization:

  • Screen multiple detergents and concentrations

  • Test different lysis methods (sonication, high pressure, freeze-thaw)

  • Optimize buffer conditions (pH, salt, glycerol content)

  • Include protease inhibitors to prevent degradation

Experimental design methodology using multivariant analysis allows systematic optimization of these parameters with fewer experiments, enabling identification of optimal conditions for soluble expression .

How can researchers address challenges in differentiating between E. fergusonii and other Escherichia species in complex biological samples?

Differentiating E. fergusonii from closely related species, particularly E. coli, can be challenging. Researchers can implement these strategies:

• Advanced molecular identification methods:

  • Multiplex PCR targeting multiple species-specific genes:

    • Beta-glucuronidase enzyme

    • Cellulose synthase protein

    • EFER13 and EFER YP regions

  • Real-time PCR with species-specific probes for quantification

  • MALDI-TOF MS with expanded reference databases

  • WGS followed by core genome MLST or ANI analysis

• Selective isolation protocols:

  • Develop enrichment media with differential carbon sources:

    • Adonitol supplementation (2%) in Simmons Citrate Agar

    • Cellobiose and arabinose as differential fermentation indicators

  • Incorporate selective antibiotics based on common resistance profiles

  • Use chromogenic substrates that distinguish metabolic capabilities

• Algorithmic approaches to species differentiation:

  • Machine learning models trained on phenotypic and genotypic data

  • Application of Random Forest algorithms to biochemical test results

  • Pattern recognition in MALDI-TOF spectra with improved databases

• Biochemical profiling optimization:

  • Extended panel of biochemical tests beyond standard API systems

  • Custom biochemical panels focusing on differentiating characteristics

  • Metabolic fingerprinting using Biolog phenotype microarrays

• Validation and confirmation:

  • Implement a tiered approach using multiple methods

  • Sequencing of multiple housekeeping genes (MLST approach)

  • Whole genome sequencing for definitive identification

  • Comparative genomic analysis with reference strains

In research settings, misidentification rates of nearly 100% have been reported when using only commercial biochemical identification kits, highlighting the necessity of molecular confirmation methods .

What experimental design approaches are most effective for studying antimicrobial resistance in E. fergusonii isolates carrying the YqhA protein?

For studying antimicrobial resistance (AMR) in E. fergusonii, a comprehensive experimental design including both traditional and advanced methods is recommended:

• Sampling and isolation strategy:

  • Implement stratified sampling across diverse sources:

    • Clinical samples (human patients)

    • Food animals (cattle, poultry, pigs)

    • Retail meat products

    • Environmental samples

  • Use appropriate selective media and molecular confirmation for accurate species identification

  • Document metadata (source, location, date, antimicrobial usage history)

• Phenotypic AMR characterization:

  • Broth microdilution for MIC determination following CLSI or EUCAST standards

  • Disk diffusion as a complementary method

  • Test panels covering multiple antibiotic classes:

    • Beta-lactams (including extended-spectrum and carbapenems)

    • Aminoglycosides

    • Fluoroquinolones

    • Tetracyclines

    • Phenicols

    • Sulfonamides and trimethoprim

    • Colistin

• Molecular AMR characterization:

  • PCR screening for common resistance genes

  • Whole genome sequencing for comprehensive resistome analysis

  • Plasmid profiling:

    • S1-PFGE for plasmid size determination

    • Replicon typing (PCR-based or WGS-based)

    • Conjugation experiments to assess transferability

• Correlation studies with YqhA:

  • Quantitative expression analysis of yqhA under antibiotic pressure

  • Construction of yqhA knockout mutants and complementation studies

  • Heterologous expression systems to assess YqhA's role in AMR

  • Proteomics to identify YqhA interactions with known AMR proteins

• Advanced statistical analysis:

  • Multivariate analysis to correlate AMR patterns with genetic determinants

  • Machine learning approaches for predictive modeling

  • Statistical tools for epidemiological analysis:

    • Spatial clustering

    • Temporal trend analysis

    • Source attribution methods

This comprehensive approach allows for robust correlation between YqhA expression, genetic background, and AMR phenotypes in E. fergusonii isolates .

What are the most appropriate control strains and reference materials for research involving E. fergusonii UPF0114 protein YqhA?

Selection of appropriate controls and reference materials is crucial for reliable research on E. fergusonii YqhA:

• Reference strains for E. fergusonii studies:

  • ATCC 35469 / DSM 13698 / CDC 0568-73 (type strain with sequenced genome)

  • Well-characterized clinical isolates with published genome sequences

  • Control strains with known antimicrobial susceptibility profiles

  • E. coli K-12 derivatives as negative controls for E. fergusonii-specific tests

• Genetic constructs as reference materials:

  • Cloned yqhA gene in expression vectors with sequence verification

  • Site-directed mutants of key residues in YqhA

  • Fluorescently tagged YqhA constructs for localization studies

  • Inducible expression systems for controlled YqhA production

• Protein standards:

  • Purified recombinant YqhA with verified identity and purity

  • Synthetic peptides corresponding to immunogenic regions of YqhA

  • Isotopically labeled YqhA for NMR studies

  • Antibodies against YqhA (polyclonal or monoclonal)

• Data reference standards:

  • Published sequence data from multiple E. fergusonii strains

  • Structural models based on homologous proteins

  • Standardized MIC interpretation criteria

  • Database references:

    • UniProt entry B7LPX2 for YqhA

    • Reference genome annotations

    • Antimicrobial resistance database entries

• Methodological controls:

  • Empty vector controls for expression studies

  • Isogenic strains lacking yqhA

  • Non-specific membrane proteins as controls for localization studies

  • Species-specific PCR controls (positive and negative)

These reference materials and controls ensure reproducibility and reliable interpretation of experimental results across different research laboratories .