Recombinant Cronobacter sakazakii UPF0114 protein ESA_00283 (ESA_00283)

How does Cronobacter sakazakii UPF0114 protein ESA_00283 relate to the reclassification of Enterobacter sakazakii?

The UPF0114 protein ESA_00283 is found in Cronobacter sakazakii, which was previously classified as Enterobacter sakazakii until 2007. The reclassification was based on comprehensive genomic analyses that led to the creation of the genus Cronobacter, which now includes seven species: C. sakazakii, C. malonaticus, C. dublinensis, C. turicensis, C. muytjensii, C. universalis, and C. zurichensis. This reclassification impacts how researchers should interpret historical studies on this protein, as older literature refers to the organism as Enterobacter sakazakii (sensu lato), while newer research specifically names Cronobacter sakazakii .

What is known about the genetic context of ESA_00283 in the Cronobacter sakazakii genome?

ESA_00283 is an ordered locus name in the Cronobacter sakazakii genome. It encodes a protein of unknown function (UPF0114 family). The gene appears to be part of the core genome of C. sakazakii rather than being located on any of the known virulence plasmids such as pESA3. While detailed genetic neighborhood analysis is limited in current literature, researchers studying this protein should consider its genomic context when interpreting functional data, particularly when comparing different strains of C. sakazakii, such as ATCC BAA-894 (the strain from which this gene was initially characterized) .

What are the optimal expression conditions for recombinant ESA_00283 protein?

For optimal expression of recombinant ESA_00283 protein, the following conditions have been established:

• Expression system: E. coli BL21 cells

• Culture medium: LB medium with appropriate antibiotic (typically 1mM Kanamycin)

• Induction: 0.05mM IPTG

• Temperature and duration: 30°C for 8 hours (similar to conditions for GroEL protein expression)

• Cell disruption: High-pressure homogenization at approximately 25 MPa

After harvesting, the protein can be purified using nickel affinity chromatography taking advantage of the His-tag. If the protein forms inclusion bodies, it may require denaturation and renaturation using urea dialysate methods similar to those described for other Cronobacter proteins .

What are the recommended storage and reconstitution protocols for ESA_00283 recombinant protein?

The recommended protocols for storage and reconstitution of ESA_00283 recombinant protein are:

Storage:

• Store at -20°C/-80°C upon receipt

• Aliquoting is necessary for multiple use

• Avoid repeated freeze-thaw cycles

• Working aliquots can be stored at 4°C for up to one week

Reconstitution:

• Briefly centrifuge the vial prior to opening to bring contents to the bottom

• Reconstitute in deionized sterile water to a concentration of 0.1-1.0 mg/mL

• Add glycerol to a final concentration of 5-50% (recommended 50%)

• Make small aliquots and store at -20°C/-80°C for long-term storage

This protocol maximizes protein stability and prevents activity loss from repeated freeze-thaw cycles .

How can researchers verify the identity and purity of recombinant ESA_00283 protein?

To verify the identity and purity of recombinant ESA_00283 protein, researchers should employ a multi-method approach:

• SDS-PAGE analysis: Should show a single predominant band at approximately 18-20 kDa (accounting for the His-tag's additional weight). Purity should be >90%.

• Western blotting: Using anti-His antibodies can confirm the presence of the His-tagged recombinant protein.

• Mass spectrometry: MALDI-TOF or LC-MS/MS can provide definitive identification through peptide mass fingerprinting or sequencing.

• N-terminal sequencing: Confirms the correct starting sequence of the expressed protein.

• Protein concentration determination: Bradford or BCA assays to determine total protein concentration.

These techniques together provide comprehensive authentication of the recombinant protein's identity and quality before experimental use .

What post-translational modifications might ESA_00283 undergo and how can they be detected?

Although specific post-translational modifications (PTMs) of ESA_00283 have not been extensively documented, based on its sequence and subcellular location, potential PTMs include:

• Phosphorylation: Possible at serine, threonine, and tyrosine residues, particularly in cytoplasmic domains

• Lipidation: Potential for palmitoylation or myristoylation given its membrane association

• Disulfide bond formation: If cysteines are present in periplasmic domains

Detection methods for these PTMs include:

• Mass spectrometry: LC-MS/MS with enrichment for specific PTMs

• Western blotting: Using PTM-specific antibodies (e.g., anti-phosphotyrosine)

• Radioisotope labeling: For metabolic labeling of lipid modifications

• Mobility shift assays: Comparing migration patterns before and after PTM-removing treatments

When investigating ESA_00283 function, researchers should consider native PTMs that may not be present in recombinant systems, particularly when expressed in E. coli, which may lack the necessary modification machinery present in Cronobacter .

How might ESA_00283 contribute to Cronobacter sakazakii virulence and pathogenicity?

While the specific role of ESA_00283 in Cronobacter sakazakii virulence has not been directly established, several lines of evidence suggest potential contributions to pathogenicity:

• Membrane localization: As a predicted membrane protein, ESA_00283 may participate in host-pathogen interactions, similar to other membrane proteins in C. sakazakii like OmpA and OmpX that are involved in epithelial cell invasion .

• Stress response: UPF0114 family proteins may play roles in stress adaptation, potentially contributing to C. sakazakii's notable ability to survive in harsh conditions, including acid stress environments (pH 3.0-3.5) and desiccation .

• Conserved presence: The gene is present across clinical isolates, suggesting a potential core function important for bacterial fitness during infection.

To definitively determine ESA_00283's role in virulence, researchers should consider:

• Gene knockout studies and virulence assessment in infection models

• Protein-protein interaction studies to identify binding partners

• Transcriptomic analysis to determine expression patterns during infection stages .

What experimental approaches can be used to study the role of ESA_00283 in bacterial adhesion and invasion?

To investigate the potential role of ESA_00283 in bacterial adhesion and invasion, researchers can employ several complementary approaches:

• Cell culture models:

  • HEp-2 epithelial cell adhesion and invasion assays

  • Caco-2 intestinal epithelial cell models

  • Brain microvascular endothelial cell models (particularly relevant for meningitis-causing strains)

• Genetic manipulation:

  • Gene knockout or knockdown (CRISPR-Cas9 or RNA interference)

  • Complementation studies

  • Overexpression analysis

• Protein interaction studies:

  • Pull-down assays using recombinant ESA_00283

  • Yeast two-hybrid screening

  • Co-immunoprecipitation with host cell factors

• Microscopy techniques:

  • Immunofluorescence to localize the protein during host cell interaction

  • Electron microscopy to visualize ultrastructural details

• Quantitative measurements:

  • Adhesion efficiency (typically measured as number of adherent bacteria per cell)

  • Invasion efficiency (calculated as percentage of initial inoculum that survives gentamicin treatment)

For reference, published studies have shown that Cronobacter sakazakii strains typically display adhesion values of approximately 22 × 10^4 CFU/mL to HEp-2 cells, with invasion efficiencies ranging from 2.5% to 5.2% .

How can recombinant ESA_00283 be used in developing diagnostic tools for Cronobacter sakazakii detection?

Recombinant ESA_00283 protein has several potential applications in developing improved diagnostic tools for Cronobacter sakazakii:

• Antibody development:

  • The purified recombinant protein can be used to generate high-affinity polyclonal or monoclonal antibodies

  • These antibodies can serve as capture or detection reagents in various immunoassay formats

• ELISA-based detection systems:

  • Sandwich ELISA using anti-ESA_00283 antibodies

  • Competitive ELISA for rapid screening

  • Potential sensitivity improvements over current culture-based methods

• Lateral flow immunochromatographic assays:

  • Point-of-use tests for field or industrial settings

  • Rapid screening of powdered infant formula during production

• Aptamer selection:

  • Using recombinant ESA_00283 as a target for SELEX (Systematic Evolution of Ligands by Exponential Enrichment)

  • Development of aptamer-based biosensors with high specificity

• Positive controls:

  • Inclusion as positive control material in molecular diagnostic kits

  • Quality control for existing detection methods

These applications may be particularly valuable in detecting Cronobacter in the viable but non-culturable state, which traditional culturing methods might miss, especially in powdered infant formula testing .

What considerations should be taken into account when using ESA_00283 for immunization and antibody production?

When using ESA_00283 for immunization and antibody production, researchers should consider several important factors:

• Protein preparation:

  • Due to its predicted membrane topology, consider using hydrophilic regions or peptide fragments for immunization

  • For full-length protein, ensure proper refolding after purification to maintain native epitopes

  • Consider detergent solubilization to maintain membrane protein structure

• Immunization strategy:

  • Choose appropriate adjuvants (Freund's complete adjuvant for initial immunization, incomplete for boosters)

  • Consider carrier protein conjugation for potentially weak immunogens

  • Plan a 3-4 immunization schedule with 2-3 week intervals

• Host selection:

  • Rabbits are suitable for polyclonal antibody production

  • Mice or rats for monoclonal antibody development

  • Consider sequence homology between ESA_00283 and host proteins to avoid tolerance issues

• Antibody purification and validation:

  • Affinity purification using immobilized recombinant protein

  • Test specificity against both recombinant protein and native protein in bacterial lysates

  • Validate for cross-reactivity with homologous proteins from related species

• Application-specific considerations:

  • For diagnostic applications, test antibody performance in the intended assay format

  • For research antibodies, validate in immunoblotting, immunofluorescence, and immunoprecipitation

The purified antibodies can be used for localization studies, functional assays, and diagnostic test development .

How can researchers investigate potential interactions between ESA_00283 and host factors during Cronobacter sakazakii infection?

To investigate potential interactions between ESA_00283 and host factors during Cronobacter sakazakii infection, researchers can employ a multi-faceted approach:

• Pull-down assays:

  • Immobilize purified recombinant ESA_00283 on an affinity column

  • Pass host cell lysates (from relevant cell types like intestinal epithelial cells or brain endothelial cells)

  • Identify binding partners using mass spectrometry

  • Confirm interactions with co-immunoprecipitation

• Yeast two-hybrid screening:

  • Use ESA_00283 (or domains) as bait against human cDNA library

  • Validate positive interactions with targeted assays

• Surface plasmon resonance (SPR):

  • Quantitative measurement of binding kinetics with purified host proteins

  • Determine affinity constants for interactions

• Infection models with genetic modification:

  • Compare wild-type to ESA_00283 mutant strains in cellular infection models

  • Assess differences in host cell responses (transcriptomic or proteomic analysis)

  • Monitor localization of host factors during infection

• Binding domain mapping:

  • Create truncation mutants to identify specific regions involved in host interactions

  • Use peptide arrays to pinpoint exact binding motifs

This systematic approach can reveal whether ESA_00283 directly interacts with host receptors, immune system components, or other cellular factors during the infection process, potentially identifying new therapeutic targets .

How does the expression of ESA_00283 vary among different sequence types of Cronobacter sakazakii, particularly the highly virulent ST4 lineage?

The expression patterns of ESA_00283 across different sequence types (STs) of Cronobacter sakazakii require further investigation, but contextual information suggests important considerations:

• Sequence type variation:

  • C. sakazakii ST4 is particularly associated with neonatal meningitis, with 9 of 12 meningitis isolates belonging to this sequence type

  • ST4 has been described as a highly stable clone with enhanced propensity for causing neonatal meningitis

  • The earliest ST4 isolate dates back to 1950 from dried milk

• Expression analysis recommendations:

  • Comparative transcriptomics across sequence types (particularly ST4 vs. non-ST4)

  • RT-qPCR validation of ESA_00283 expression during various growth phases

  • Proteomics analysis to confirm translation and protein abundance

• Functional implications:

  • Determine if expression differences correlate with virulence phenotypes

  • Investigate if regulatory elements controlling ESA_00283 differ between STs

  • Consider whether post-transcriptional regulation varies among lineages

• Research design considerations:

  • Include diverse clinical and environmental isolates representing multiple STs

  • Test expression under conditions mimicking host environments

  • Consider temporal expression patterns during infection process

Understanding these expression patterns may provide insights into why certain sequence types, particularly ST4, show enhanced virulence and tissue tropism for the central nervous system .

What is the impact of viable but non-culturable (VBNC) state on ESA_00283 expression and function in Cronobacter sakazakii?

The viable but non-culturable (VBNC) state in Cronobacter sakazakii has significant implications for understanding ESA_00283 expression and function:

• VBNC state characteristics in C. sakazakii:

  • C. sakazakii can enter VBNC state under stress conditions (e.g., acid exposure at pH 3.0)

  • VBNC cells remain viable but cannot be detected by standard culture methods

  • This state may contribute to false negatives in quality control testing

• Research approaches for ESA_00283 in VBNC state:

  • Transcriptomic analysis comparing culturable vs. VBNC cells

  • Proteomic analysis of membrane fraction in VBNC state

  • Immunological detection of ESA_00283 in VBNC cells

  • Fluorescent reporter constructs to monitor gene expression during VBNC transition

• Resuscitation from VBNC:

  • Test whether ESA_00283 plays a role in resuscitation from VBNC state

  • Investigate ESA_00283 expression changes during resuscitation with various stimulants:

    • Sodium pyruvate

    • Catalase

    • Tween 20

    • Autoinducers (quorum sensing molecules)

• Methodological considerations:

  • Flow cytometry with viability dyes to distinguish VBNC from dead cells

  • Single-cell analysis techniques to account for population heterogeneity

  • Molecular detection methods that don't rely on culturability

Understanding ESA_00283's role in the VBNC state could be crucial for improving detection methods and understanding environmental persistence mechanisms .

How does recombinant ESA_00283 protein compare to the native protein in terms of structural features and functional activities?

The comparison between recombinant and native ESA_00283 protein reveals important considerations for researchers:

• Structural differences:

  • Recombinant ESA_00283 typically contains an N-terminal His-tag, which may alter protein folding or functionality

  • Expression in E. coli may result in different lipid environments compared to native Cronobacter membrane

  • Potential differences in post-translational modifications between expression systems

• Functional comparison methodologies:

  • Circular dichroism (CD) spectroscopy to compare secondary structure elements

  • Limited proteolysis patterns to assess tertiary structure similarities

  • Activity assays (once function is established) to compare functional capacity

  • Antibody recognition tests using antibodies raised against native protein

• Optimization strategies:

  • Try multiple expression systems (bacterial, yeast, mammalian) to find optimal folding

  • Test various purification conditions to maintain native-like structure

  • Consider expression with the protein's natural signal sequence

  • For membrane proteins, consider nanodiscs or liposome reconstitution

• Validation approaches:

  • Cross-validation with multiple biophysical techniques

  • Functional complementation in knockout strains

  • Structural analysis by NMR or X-ray crystallography when possible

These comparisons are crucial when using recombinant ESA_00283 as a substitute for the native protein in research applications, particularly for structural studies, antibody production, and functional characterization .

Frequently Asked Questions for Researchers on Recombinant Cronobacter sakazakii UPF0114 protein ESA_00283

How does Cronobacter sakazakii UPF0114 protein ESA_00283 relate to the reclassification of Enterobacter sakazakii?

The UPF0114 protein ESA_00283 is found in Cronobacter sakazakii, which was previously classified as Enterobacter sakazakii until 2007. The reclassification was based on comprehensive genomic analyses that led to the creation of the genus Cronobacter, which now includes seven species: C. sakazakii, C. malonaticus, C. dublinensis, C. turicensis, C. muytjensii, C. universalis, and C. zurichensis. This reclassification impacts how researchers should interpret historical studies on this protein, as older literature refers to the organism as Enterobacter sakazakii (sensu lato), while newer research specifically names Cronobacter sakazakii .

What is known about the genetic context of ESA_00283 in the Cronobacter sakazakii genome?

ESA_00283 is an ordered locus name in the Cronobacter sakazakii genome. It encodes a protein of unknown function (UPF0114 family). The gene appears to be part of the core genome of C. sakazakii rather than being located on any of the known virulence plasmids such as pESA3. While detailed genetic neighborhood analysis is limited in current literature, researchers studying this protein should consider its genomic context when interpreting functional data, particularly when comparing different strains of C. sakazakii, such as ATCC BAA-894 (the strain from which this gene was initially characterized) .

What are the optimal expression conditions for recombinant ESA_00283 protein?

For optimal expression of recombinant ESA_00283 protein, the following conditions have been established:

• Expression system: E. coli BL21 cells

• Culture medium: LB medium with appropriate antibiotic (typically 1mM Kanamycin)

• Induction: 0.05mM IPTG

• Temperature and duration: 30°C for 8 hours (similar to conditions for GroEL protein expression)

• Cell disruption: High-pressure homogenization at approximately 25 MPa

After harvesting, the protein can be purified using nickel affinity chromatography taking advantage of the His-tag. If the protein forms inclusion bodies, it may require denaturation and renaturation using urea dialysate methods similar to those described for other Cronobacter proteins .

What are the recommended storage and reconstitution protocols for ESA_00283 recombinant protein?

The recommended protocols for storage and reconstitution of ESA_00283 recombinant protein are:

Storage:

• Store at -20°C/-80°C upon receipt

• Aliquoting is necessary for multiple use

• Avoid repeated freeze-thaw cycles

• Working aliquots can be stored at 4°C for up to one week

Reconstitution:

• Briefly centrifuge the vial prior to opening to bring contents to the bottom

• Reconstitute in deionized sterile water to a concentration of 0.1-1.0 mg/mL

• Add glycerol to a final concentration of 5-50% (recommended 50%)

• Make small aliquots and store at -20°C/-80°C for long-term storage

This protocol maximizes protein stability and prevents activity loss from repeated freeze-thaw cycles .

How can researchers verify the identity and purity of recombinant ESA_00283 protein?

To verify the identity and purity of recombinant ESA_00283 protein, researchers should employ a multi-method approach:

• SDS-PAGE analysis: Should show a single predominant band at approximately 18-20 kDa (accounting for the His-tag's additional weight). Purity should be >90%.

• Western blotting: Using anti-His antibodies can confirm the presence of the His-tagged recombinant protein.

• Mass spectrometry: MALDI-TOF or LC-MS/MS can provide definitive identification through peptide mass fingerprinting or sequencing.

• N-terminal sequencing: Confirms the correct starting sequence of the expressed protein.

• Protein concentration determination: Bradford or BCA assays to determine total protein concentration.

These techniques together provide comprehensive authentication of the recombinant protein's identity and quality before experimental use .

What post-translational modifications might ESA_00283 undergo and how can they be detected?

Although specific post-translational modifications (PTMs) of ESA_00283 have not been extensively documented, based on its sequence and subcellular location, potential PTMs include:

• Phosphorylation: Possible at serine, threonine, and tyrosine residues, particularly in cytoplasmic domains

• Lipidation: Potential for palmitoylation or myristoylation given its membrane association

• Disulfide bond formation: If cysteines are present in periplasmic domains

Detection methods for these PTMs include:

• Mass spectrometry: LC-MS/MS with enrichment for specific PTMs

• Western blotting: Using PTM-specific antibodies (e.g., anti-phosphotyrosine)

• Radioisotope labeling: For metabolic labeling of lipid modifications

• Mobility shift assays: Comparing migration patterns before and after PTM-removing treatments

When investigating ESA_00283 function, researchers should consider native PTMs that may not be present in recombinant systems, particularly when expressed in E. coli, which may lack the necessary modification machinery present in Cronobacter .

How might ESA_00283 contribute to Cronobacter sakazakii virulence and pathogenicity?

While the specific role of ESA_00283 in Cronobacter sakazakii virulence has not been directly established, several lines of evidence suggest potential contributions to pathogenicity:

• Membrane localization: As a predicted membrane protein, ESA_00283 may participate in host-pathogen interactions, similar to other membrane proteins in C. sakazakii like OmpA and OmpX that are involved in epithelial cell invasion .

• Stress response: UPF0114 family proteins may play roles in stress adaptation, potentially contributing to C. sakazakii's notable ability to survive in harsh conditions, including acid stress environments (pH 3.0-3.5) and desiccation .

• Conserved presence: The gene is present across clinical isolates, suggesting a potential core function important for bacterial fitness during infection.

To definitively determine ESA_00283's role in virulence, researchers should consider:

• Gene knockout studies and virulence assessment in infection models

• Protein-protein interaction studies to identify binding partners

• Transcriptomic analysis to determine expression patterns during infection stages .

What experimental approaches can be used to study the role of ESA_00283 in bacterial adhesion and invasion?

To investigate the potential role of ESA_00283 in bacterial adhesion and invasion, researchers can employ several complementary approaches:

• Cell culture models:

  • HEp-2 epithelial cell adhesion and invasion assays

  • Caco-2 intestinal epithelial cell models

  • Brain microvascular endothelial cell models (particularly relevant for meningitis-causing strains)

• Genetic manipulation:

  • Gene knockout or knockdown (CRISPR-Cas9 or RNA interference)

  • Complementation studies

  • Overexpression analysis

• Protein interaction studies:

  • Pull-down assays using recombinant ESA_00283

  • Yeast two-hybrid screening

  • Co-immunoprecipitation with host cell factors

• Microscopy techniques:

  • Immunofluorescence to localize the protein during host cell interaction

  • Electron microscopy to visualize ultrastructural details

• Quantitative measurements:

  • Adhesion efficiency (typically measured as number of adherent bacteria per cell)

  • Invasion efficiency (calculated as percentage of initial inoculum that survives gentamicin treatment)

For reference, published studies have shown that Cronobacter sakazakii strains typically display adhesion values of approximately 22 × 10^4 CFU/mL to HEp-2 cells, with invasion efficiencies ranging from 2.5% to 5.2% .

How can recombinant ESA_00283 be used in developing diagnostic tools for Cronobacter sakazakii detection?

Recombinant ESA_00283 protein has several potential applications in developing improved diagnostic tools for Cronobacter sakazakii:

• Antibody development:

  • The purified recombinant protein can be used to generate high-affinity polyclonal or monoclonal antibodies

  • These antibodies can serve as capture or detection reagents in various immunoassay formats

• ELISA-based detection systems:

  • Sandwich ELISA using anti-ESA_00283 antibodies

  • Competitive ELISA for rapid screening

  • Potential sensitivity improvements over current culture-based methods

• Lateral flow immunochromatographic assays:

  • Point-of-use tests for field or industrial settings

  • Rapid screening of powdered infant formula during production

• Aptamer selection:

  • Using recombinant ESA_00283 as a target for SELEX (Systematic Evolution of Ligands by Exponential Enrichment)

  • Development of aptamer-based biosensors with high specificity

• Positive controls:

  • Inclusion as positive control material in molecular diagnostic kits

  • Quality control for existing detection methods

These applications may be particularly valuable in detecting Cronobacter in the viable but non-culturable state, which traditional culturing methods might miss, especially in powdered infant formula testing .

What considerations should be taken into account when using ESA_00283 for immunization and antibody production?

When using ESA_00283 for immunization and antibody production, researchers should consider several important factors:

• Protein preparation:

  • Due to its predicted membrane topology, consider using hydrophilic regions or peptide fragments for immunization

  • For full-length protein, ensure proper refolding after purification to maintain native epitopes

  • Consider detergent solubilization to maintain membrane protein structure

• Immunization strategy:

  • Choose appropriate adjuvants (Freund's complete adjuvant for initial immunization, incomplete for boosters)

  • Consider carrier protein conjugation for potentially weak immunogens

  • Plan a 3-4 immunization schedule with 2-3 week intervals

• Host selection:

  • Rabbits are suitable for polyclonal antibody production

  • Mice or rats for monoclonal antibody development

  • Consider sequence homology between ESA_00283 and host proteins to avoid tolerance issues

• Antibody purification and validation:

  • Affinity purification using immobilized recombinant protein

  • Test specificity against both recombinant protein and native protein in bacterial lysates

  • Validate for cross-reactivity with homologous proteins from related species

• Application-specific considerations:

  • For diagnostic applications, test antibody performance in the intended assay format

  • For research antibodies, validate in immunoblotting, immunofluorescence, and immunoprecipitation

The purified antibodies can be used for localization studies, functional assays, and diagnostic test development .

How can researchers investigate potential interactions between ESA_00283 and host factors during Cronobacter sakazakii infection?

To investigate potential interactions between ESA_00283 and host factors during Cronobacter sakazakii infection, researchers can employ a multi-faceted approach:

• Pull-down assays:

  • Immobilize purified recombinant ESA_00283 on an affinity column

  • Pass host cell lysates (from relevant cell types like intestinal epithelial cells or brain endothelial cells)

  • Identify binding partners using mass spectrometry

  • Confirm interactions with co-immunoprecipitation

• Yeast two-hybrid screening:

  • Use ESA_00283 (or domains) as bait against human cDNA library

  • Validate positive interactions with targeted assays

• Surface plasmon resonance (SPR):

  • Quantitative measurement of binding kinetics with purified host proteins

  • Determine affinity constants for interactions

• Infection models with genetic modification:

  • Compare wild-type to ESA_00283 mutant strains in cellular infection models

  • Assess differences in host cell responses (transcriptomic or proteomic analysis)

  • Monitor localization of host factors during infection

• Binding domain mapping:

  • Create truncation mutants to identify specific regions involved in host interactions

  • Use peptide arrays to pinpoint exact binding motifs

This systematic approach can reveal whether ESA_00283 directly interacts with host receptors, immune system components, or other cellular factors during the infection process, potentially identifying new therapeutic targets .

How does the expression of ESA_00283 vary among different sequence types of Cronobacter sakazakii, particularly the highly virulent ST4 lineage?

The expression patterns of ESA_00283 across different sequence types (STs) of Cronobacter sakazakii require further investigation, but contextual information suggests important considerations:

• Sequence type variation:

  • C. sakazakii ST4 is particularly associated with neonatal meningitis, with 9 of 12 meningitis isolates belonging to this sequence type

  • ST4 has been described as a highly stable clone with enhanced propensity for causing neonatal meningitis

  • The earliest ST4 isolate dates back to 1950 from dried milk

• Expression analysis recommendations:

  • Comparative transcriptomics across sequence types (particularly ST4 vs. non-ST4)

  • RT-qPCR validation of ESA_00283 expression during various growth phases

  • Proteomics analysis to confirm translation and protein abundance

• Functional implications:

  • Determine if expression differences correlate with virulence phenotypes

  • Investigate if regulatory elements controlling ESA_00283 differ between STs

  • Consider whether post-transcriptional regulation varies among lineages

• Research design considerations:

  • Include diverse clinical and environmental isolates representing multiple STs

  • Test expression under conditions mimicking host environments

  • Consider temporal expression patterns during infection process

Understanding these expression patterns may provide insights into why certain sequence types, particularly ST4, show enhanced virulence and tissue tropism for the central nervous system .

What is the impact of viable but non-culturable (VBNC) state on ESA_00283 expression and function in Cronobacter sakazakii?

The viable but non-culturable (VBNC) state in Cronobacter sakazakii has significant implications for understanding ESA_00283 expression and function:

• VBNC state characteristics in C. sakazakii:

  • C. sakazakii can enter VBNC state under stress conditions (e.g., acid exposure at pH 3.0)

  • VBNC cells remain viable but cannot be detected by standard culture methods

  • This state may contribute to false negatives in quality control testing

• Research approaches for ESA_00283 in VBNC state:

  • Transcriptomic analysis comparing culturable vs. VBNC cells

  • Proteomic analysis of membrane fraction in VBNC state

  • Immunological detection of ESA_00283 in VBNC cells

  • Fluorescent reporter constructs to monitor gene expression during VBNC transition

• Resuscitation from VBNC:

  • Test whether ESA_00283 plays a role in resuscitation from VBNC state

  • Investigate ESA_00283 expression changes during resuscitation with various stimulants:

    • Sodium pyruvate

    • Catalase

    • Tween 20

    • Autoinducers (quorum sensing molecules)

• Methodological considerations:

  • Flow cytometry with viability dyes to distinguish VBNC from dead cells

  • Single-cell analysis techniques to account for population heterogeneity

  • Molecular detection methods that don't rely on culturability

Understanding ESA_00283's role in the VBNC state could be crucial for improving detection methods and understanding environmental persistence mechanisms .

How does recombinant ESA_00283 protein compare to the native protein in terms of structural features and functional activities?

The comparison between recombinant and native ESA_00283 protein reveals important considerations for researchers:

• Structural differences:

  • Recombinant ESA_00283 typically contains an N-terminal His-tag, which may alter protein folding or functionality

  • Expression in E. coli may result in different lipid environments compared to native Cronobacter membrane

  • Potential differences in post-translational modifications between expression systems

• Functional comparison methodologies:

  • Circular dichroism (CD) spectroscopy to compare secondary structure elements

  • Limited proteolysis patterns to assess tertiary structure similarities

  • Activity assays (once function is established) to compare functional capacity

  • Antibody recognition tests using antibodies raised against native protein

• Optimization strategies:

  • Try multiple expression systems (bacterial, yeast, mammalian) to find optimal folding

  • Test various purification conditions to maintain native-like structure

  • Consider expression with the protein's natural signal sequence

  • For membrane proteins, consider nanodiscs or liposome reconstitution

• Validation approaches:

  • Cross-validation with multiple biophysical techniques

  • Functional complementation in knockout strains

  • Structural analysis by NMR or X-ray crystallography when possible