Recombinant Burkholderia thailandensis Probable intracellular septation protein A (BTH_I2138)

How is Recombinant BTH_I2138 Protein Typically Expressed and Purified?

Recombinant BTH_I2138 is typically expressed in E. coli expression systems following these methodological steps:

• Cloning and Vector Construction:

  • The BTH_I2138 gene (full-length 1-176 aa) is amplified from B. thailandensis genomic DNA

  • The gene is cloned into an expression vector (commonly pET-28a) with an N-terminal His-tag fusion

  • Sequence verification confirms correct insertion and orientation

• Expression Conditions:

  • Transformation into E. coli BL21(DE3) strain

  • Culture growth at 37°C to mid-log phase

  • Induction with IPTG (typically 0.5-1.0 mM)

  • Post-induction growth at reduced temperature (16-25°C) for 4-18 hours

• Purification Protocol:

  • Cell lysis by sonication in a Tris/PBS-based buffer

  • Affinity chromatography using His-Trap columns

  • Elution with imidazole gradient

  • Further purification by size-exclusion chromatography if needed

• Storage Recommendations:

  • Lyophilization or storage in Tris/PBS-based buffer with 6% Trehalose at pH 8.0

  • Aliquoting with 50% glycerol for long-term storage at -20°C/-80°C

  • Avoiding repeated freeze-thaw cycles, with working aliquots stored at 4°C for up to one week

The typical purity achieved is greater than 90% as determined by SDS-PAGE analysis, making the protein suitable for various research applications.

What is the Structure-Function Relationship of BTH_I2138?

BTH_I2138's structure directly relates to its function in bacterial cell division:

• Membrane Topology:

  • The protein contains multiple transmembrane domains that anchor it within the inner bacterial membrane

  • Hydrophobic regions form alpha-helical transmembrane segments that span the lipid bilayer

  • Hydrophilic loops connect the transmembrane segments and may interact with cytoplasmic or periplasmic proteins

• Functional Domains:

  • N-terminal region: Contains membrane-targeting sequences

  • Central region: Likely involved in protein-protein interactions with division machinery

  • C-terminal region: May participate in signaling or regulatory interactions

• Structural Homology:

  • Similar structural features are found in YciB family proteins across bacterial species

  • Conserved motifs suggest common mechanistic functions in cell division

• Predicted Role in Cell Division:

  • Localization to the division septum during cell division

  • Coordination with other division proteins to ensure proper septum formation

  • Potential role in recruiting or stabilizing divisome components

While a high-resolution structure has not yet been determined, computational models suggest a multi-pass membrane protein with domains extending into both the cytoplasm and periplasm .

What Methods Can Be Used to Assess BTH_I2138 Expression Levels?

Researchers can employ several complementary techniques to quantify BTH_I2138 expression:

• Quantitative Real-Time PCR (qRT-PCR):

  • Principle: Measures BTH_I2138 mRNA levels using gene-specific primers

  • Protocol:

    • Extract total RNA from B. thailandensis cultures

    • Synthesize cDNA using reverse transcriptase

    • Perform qPCR with BTH_I2138-specific primers

    • Normalize to housekeeping genes (e.g., 16S rRNA)

  • Advantages: High sensitivity, quantitative, relatively simple

  • Limitations: Measures transcript but not protein levels

• Western Blot Analysis:

  • Principle: Detects BTH_I2138 protein using specific antibodies

  • Protocol:

    • Prepare bacterial lysates from various growth conditions

    • Separate proteins by SDS-PAGE

    • Transfer to membrane and probe with anti-BTH_I2138 antibodies

    • Use isocitrate dehydrogenase (ICDH) as loading control

  • Advantages: Directly measures protein levels, can detect post-translational modifications

  • Limitations: Requires specific antibodies, semi-quantitative

• Reporter Gene Fusions:

  • Principle: BTH_I2138 promoter drives expression of a reporter gene (GFP, luciferase)

  • Protocol:

    • Clone BTH_I2138 promoter upstream of reporter gene

    • Integrate construct into B. thailandensis genome

    • Measure reporter activity under various conditions

  • Advantages: Real-time monitoring, in vivo analysis

  • Limitations: Measures transcriptional activity, not protein levels

• Mass Spectrometry-Based Proteomics:

  • Principle: Direct identification and quantification of BTH_I2138 peptides

  • Protocol:

    • Extract proteins from B. thailandensis

    • Digest with trypsin and analyze by LC-MS/MS

    • Quantify BTH_I2138-specific peptides

  • Advantages: Highly specific, can be quantitative, no antibodies needed

  • Limitations: Complex methodology, expensive equipment

This multi-technique approach allows researchers to comprehensively analyze BTH_I2138 expression at both transcriptional and translational levels, providing insights into its regulation during different growth phases or environmental conditions .

What Experimental Designs Are Most Effective for Studying the Function of BTH_I2138 in Cell Division?

To rigorously investigate BTH_I2138's role in cell division, researchers should implement systematic experimental designs that establish causal relationships:

These experimental designs should incorporate proper controls, randomization, and blinding to minimize bias. Research by the PLOS One study found that "only 12% of all 271 studies in the sample" reported random allocation, and even fewer (9%) provided details of the randomization method , highlighting the importance of methodological rigor.

How Can Single-Case Experimental Designs Be Applied to Study BTH_I2138 Function?

Single-case experimental designs (SCEDs) offer powerful approaches for studying BTH_I2138 function by enabling detailed analysis of temporal relationships and causal mechanisms:

• ABAB Reversal Design Application:

  Phase	Condition	Measurement
  A₁ (Baseline)	Wild-type BTH_I2138 expression	Cell division rate, septum formation
  B₁ (Intervention)	Conditional BTH_I2138 depletion	Cell division rate, septum formation
  A₂ (Return to baseline)	Restoration of BTH_I2138 expression	Cell division rate, septum formation
  B₂ (Reintroduction)	Second depletion of BTH_I2138	Cell division rate, septum formation

  This design provides "three replications of treatment effects (A₁ versus B₁, B₁ versus A₂, A₂ versus B₂)," establishing experimental control and demonstrating causality .

• Multiple Baseline Design:

  • Create three bacterial cultures from the same parent culture

  • Introduce BTH_I2138 depletion at different time points for each culture

  • Monitor cell division parameters continuously across all cultures

  • Stagger intervention timing to control for time-dependent effects

• Changing Criterion Design:

  • Use a titratable expression system for BTH_I2138

  • Gradually reduce expression levels at predetermined intervals

  • Measure corresponding changes in cell division parameters

  • Establish dose-response relationship between BTH_I2138 levels and function

• Combined Designs:
  "Combined reversal and multiple baseline designs... focus on demonstrating experimental control of the relationship between treatment and outcome" . This approach would involve multiple bacterial cultures subjected to different sequences of BTH_I2138 modulation.

SCEDs are particularly valuable for BTH_I2138 research as they allow for precise control of experimental conditions and detailed temporal analysis of phenotypic changes, with each bacterial culture serving as its own control. These designs can "be adapted for personalized medicine" approaches and provide robust "demonstration of treatment effects" .

What Are the Challenges in Expressing Full-Length BTH_I2138 and How Can They Be Overcome?

Expressing recombinant full-length BTH_I2138 presents several technical challenges that require specific strategies:

• Expression Challenges and Solutions:

  Challenge	Solution	Methodological Details
  Membrane protein toxicity	Use specialized E. coli strains	C41(DE3) and C43(DE3) strains specifically designed for toxic membrane proteins
  Hydrophobicity issues	Optimize solubilization conditions	Screen detergents (DDM, LDAO, FC-12) for optimal extraction
  Rare codon usage	Codon optimization or use of CodonPlus strains	Adapt BTH_I2138 sequence to E. coli codon bias
  Truncated products	Dual-tagging strategy	"Expression vectors with fusion labels on both ends can be used to distinguish full-length proteins from truncated proteins"
  Low expression levels	Optimize induction parameters	Reduce temperature (16-18°C), lower IPTG concentration (0.1-0.2 mM), extend induction time (18-24h)

• Protein Structure Analysis:
  "To ensure the acquisition of full-length proteins... increasing the imidazole concentration at elution" can help separate full-length protein from truncated forms. Additionally, "to solve these problems, researchers need to analyze the protein sequence and secondary structure, and adopt corresponding strategies to optimize the expression conditions" .

• Purification Optimization:

  • Two-step purification approach: IMAC followed by size exclusion chromatography

  • Addition of glycerol (5-10%) to all buffers to enhance stability

  • Use of protease inhibitors to prevent degradation

  • Careful pH optimization (typically pH 7.5-8.5)

• Stabilization Strategies:

  • Reconstitution into nanodiscs or liposomes for native-like membrane environment

  • Addition of specific lipids that enhance stability

  • Use of fusion partners (MBP, SUMO) that increase solubility

  • Storage in Tris/PBS-based buffer with 6% trehalose

By systematically addressing these challenges, researchers can achieve expression of functional, full-length BTH_I2138 suitable for structural and functional studies. The methods developed for BTH_I2138 can also serve as a model for expression of other challenging membrane proteins from Burkholderia species.

How Does BTH_I2138 Expression Change During Different Growth Phases of B. thailandensis?

Understanding how BTH_I2138 expression varies across growth phases provides insights into its regulatory mechanisms and functional significance:

• Expression Pattern Analysis:
  Based on recent transcriptome-proteome profiling in B. thailandensis during transition to stationary phase, we can infer potential BTH_I2138 expression patterns:

  Growth Phase	Expected BTH_I2138 mRNA Level	Expected BTH_I2138 Protein Level	Biological Significance
  Early exponential	Moderate-high	Moderate	Active cell division phase
  Mid-exponential	High	High	Peak division activity
  Late exponential	Decreasing	Sustained	Preparation for stationary phase
  Early stationary	Low	Moderate	Reduced division activity
  Late stationary	Very low	Low	Minimal division

  This pattern would align with the observation that "proteins related to fatty acid degradation and butanoate metabolism accumulated along with proteins involved in synthesis of secondary metabolites" while "ribosomal proteins as well as the house-keeping iron-sulfur biogenesis proteins" were downregulated during stationary phase .

• Methodological Approach:
  To specifically study BTH_I2138 expression:

  • Collect samples at defined time points (OD600 = 0.2, 0.5, 1.0, 1.5, 2.0)

  • Extract RNA for qRT-PCR analysis of BTH_I2138 transcripts

  • Prepare protein samples for Western blot with anti-BTH_I2138 antibodies

  • Use RNA-Seq and proteomics for global expression context

• Regulatory Mechanisms:
  "An only modest correlation between transcriptome and proteome changes was seen, and the RpoS sigma factor was not significantly increased during early stationary phase" , suggesting that BTH_I2138 might be subject to complex post-transcriptional regulation.

• Integration with Global Expression Data:
  The study identified "928 differentially expressed genes and 832 differentially expressed proteins" during stationary phase entry, providing context for understanding BTH_I2138 regulation within the broader cellular adaptation processes.

What is the Relationship Between BTH_I2138 and the c-di-GMP Signaling Pathway in B. thailandensis?

The potential connection between BTH_I2138 and c-di-GMP signaling represents an intriguing research direction that could reveal novel regulatory mechanisms:

• Background on c-di-GMP Signaling in B. thailandensis:
  "As a key bacterial second messenger, cyclic di-GMP (c-di-GMP) regulates various physiological processes, such as motility, biofilm formation, and virulence. Cellular c-di-GMP levels are regulated by the opposing activities of diguanylate cyclases (DGCs) and phosphodiesterases (PDEs)" .

• Hypothetical Connections and Experimental Approaches:

  Hypothesis	Experimental Approach	Expected Outcome if Positive
  BTH_I2138 is regulated by c-di-GMP	Monitor BTH_I2138 expression in ΔpdcA, ΔpdcB, and ΔpdcC mutants	Altered BTH_I2138 levels in mutants compared to wild-type
  BTH_I2138 affects c-di-GMP levels	Measure c-di-GMP in ΔBTH_I2138 mutant	Changed c-di-GMP concentration in mutant
  BTH_I2138 interacts with c-di-GMP pathway components	Co-immunoprecipitation with PdcA, PdcB, or PdcC	Detection of protein-protein interactions
  BTH_I2138 mutation affects c-di-GMP-regulated phenotypes	Assess biofilm formation and motility in ΔBTH_I2138	Altered phenotypes similar to c-di-GMP pathway mutants

• Methodological Details:

  • Co-immunoprecipitation: "Co-IP studies using TSHR (left panel) or CD40 antibodies (right panel) show that TSHR antibody pulls down TSHR and CD40, and CD40 antibody also pulls down both proteins, indicating physical contact between the 2 proteins"

  • Bacterial two-hybrid system: "The bacterial hybrid plasmids pKT25M-pas, pKT25M-ggdef, pKT25M-pdcB, pUT18CM-pdcB, and pUT18CM-pdcC were constructed" - similar approach could be applied to BTH_I2138

• Potential Biological Significance:
  "The observation that homologous operons of pdcABC are widespread among betaproteobacteria and gammaproteobacteria suggests a general mechanism by which the intracellular concentration of c-di-GMP is modulated to coordinate bacterial behavior and virulence" . If BTH_I2138 interacts with this pathway, it would reveal a novel link between cell division and other bacterial behaviors regulated by c-di-GMP.

Investigating these potential connections could uncover previously unknown mechanisms coordinating cell division with biofilm formation, motility, and virulence in Burkholderia species, potentially revealing new targets for antimicrobial development.

How Can Researchers Assess the Role of BTH_I2138 in Virulence Using B. thailandensis as a Model for B. pseudomallei?

B. thailandensis provides an excellent BSL-1 model system for studying virulence mechanisms relevant to the highly pathogenic B. pseudomallei:

• Advantages of B. thailandensis as a Model:
  "B. thailandensis could be utilized as an attractive model system to facilitate the study of the role of the Bsa TTSS during Burkholderia infection, since, in contrast to the mandated B. pseudomallei working conditions, work with B. thailandensis does not require a biosafety level 3 (BSL-3) containment facility and there is no restriction on the use of antibiotic-resistance markers for its genetic manipulation" .

• Experimental Strategy for Assessing BTH_I2138's Role in Virulence:

  Experimental Approach	Methodology	Expected Outcome if BTH_I2138 Affects Virulence
  Generation of BTH_I2138 mutants	Allelic exchange mutagenesis	Clean deletion mutant with complemented control strain
  Cell invasion assays	Infection of macrophage cell lines (e.g., RAW264.7)	Changes in invasion efficiency
  Intracellular replication	Gentamicin protection assay with time course	Altered replication kinetics in host cells
  T3SS effector secretion	Western blot analysis of culture supernatants	"BipD in the culture supernatants of relevant B. thailandensis strains was probed for using specific anti-BipD antibody... For the pellet fraction, isocitrate dehydrogenase (ICDH) was used as a loading control"
  Actin-based motility	Fluorescence microscopy of infected cells	Differences in actin tail formation
  Animal infection models	Galleria mellonella larvae infection	Altered survival rates of infected larvae

• T3SS Assay Details:
  "Deletion of pdcA or pdcB resulted in significantly increased secretion of BipD and deletion of pdcC leads to significantly reduced secretion of BipD compared with the wild-type strain... The expression of pdcA or pdcC in the corresponding mutant restored the secretion of BipD to wild-type levels" . Similar approaches could be used to assess if BTH_I2138 affects T3SS function.

• Translation to B. pseudomallei:

  • Sequence comparison of BTH_I2138 with B. pseudomallei homolog

  • Conservation analysis of potential interaction partners

  • Validation of key findings in B. pseudomallei (if BSL-3 facilities available)

This systematic approach leverages the advantages of B. thailandensis while generating data relevant to understanding virulence mechanisms in the more pathogenic B. pseudomallei, potentially revealing new aspects of how cell division proteins like BTH_I2138 may influence bacterial pathogenesis.

What Techniques Can Be Used to Study Protein-Protein Interactions Involving BTH_I2138?

Investigating protein-protein interactions is crucial for understanding BTH_I2138's role in cell division networks:

• Co-immunoprecipitation (Co-IP):

  • Methodology: "Co-IP studies using TSHR (left panel) or CD40 antibodies (right panel) show that TSHR antibody pulls down TSHR and CD40, and CD40 antibody also pulls down both proteins, indicating physical contact between the 2 proteins"

  • Application to BTH_I2138: Generate specific antibodies against BTH_I2138, perform immunoprecipitation, and identify co-precipitated proteins by mass spectrometry

  • Advantages: Detects native interactions in cellular context

  • Challenges: Requires specific antibodies, membrane protein solubilization issues

• Bacterial Two-Hybrid System:

  • Methodology: "The bacterial hybrid plasmids pKT25M-pas, pKT25M-ggdef, pKT25M-pdcB, pUT18CM-pdcB, and pUT18CM-pdcC were constructed in similar manners by using the primers listed in Table 2"

  • Application to BTH_I2138: Create fusion constructs with BTH_I2138 and potential interacting partners

  • Advantages: Specifically designed for bacterial proteins, works well for membrane proteins

  • Challenges: May detect non-physiological interactions

• Proximity-Dependent Biotin Identification (BioID):

  Step	Procedure	Technical Considerations
  1	Create fusion of BTH_I2138 with BirA* biotin ligase	Confirm functionality of fusion protein
  2	Express in B. thailandensis	Optimize expression level
  3	Add biotin to growth medium	Typically 50 μM biotin for 24h
  4	Lyse cells and purify biotinylated proteins	Use stringent washing conditions
  5	Identify biotinylated proteins by mass spectrometry	Compare to control samples

  • Advantages: Detects transient interactions, works in native cellular environment

  • Challenges: May identify proteins in proximity but not directly interacting

• Förster Resonance Energy Transfer (FRET):

  • Methodology: Create fluorescent protein fusions to BTH_I2138 and candidate partners

  • Application: Express in B. thailandensis and measure energy transfer between fluorophores

  • Advantages: Can detect interactions in live cells

  • Challenges: Requires careful control experiments, potential interference of fluorescent tags

• Cross-linking Mass Spectrometry:

  • Methodology: Treat cells with cross-linking reagents, purify BTH_I2138, digest, and identify cross-linked peptides

  • Advantages: Can capture transient interactions, identifies specific interaction sites

  • Challenges: Complex data analysis, requires high-resolution mass spectrometry

These complementary approaches provide a comprehensive strategy for mapping BTH_I2138's protein interaction network, revealing its role in cell division and potentially uncovering connections to other cellular processes such as virulence or stress response.

How Do Mutations in BTH_I2138 Affect Cell Division and Bacterial Morphology?

Systematic characterization of BTH_I2138 mutations provides critical insights into structure-function relationships:

• Mutation Strategy and Analysis:

  Mutation Type	Design Approach	Analysis Method	Expected Phenotype
  Complete deletion	Allelic exchange	Phase contrast microscopy	Potential filamentous growth or division defects
  Conserved residue substitutions	Site-directed mutagenesis	Time-lapse microscopy	Varied severity based on residue importance
  Domain deletions	In-frame deletions	Electron microscopy	Domain-specific functional defects
  C-terminal/N-terminal truncations	Premature stop codons	Fluorescent microscopy with membrane stains	Insights into terminal region functions

• Microscopy Analysis Protocol:

  • Fix bacterial cells with 4% paraformaldehyde

  • Stain membranes with FM4-64 (red) and DNA with DAPI (blue)

  • Image using confocal microscopy

  • Quantify cell length, width, and nucleoid positioning

  • Perform statistical analysis comparing mutants to wild-type

• Morphological Parameters to Measure:

  Parameter	Measurement Method	Significance
  Cell length	Phase contrast imaging with automated cell detection	Indicates division frequency
  Cell width	Phase contrast imaging with automated cell detection	Reflects cell wall synthesis
  Septum positioning	Membrane staining	Shows division site selection accuracy
  Nucleoid segregation	DNA staining	Reveals chromosome partitioning
  Z-ring formation	FtsZ-GFP fusion imaging	Indicates divisome assembly

• Experimental Controls:

  • Include wild-type strain in all experiments

  • Create complemented strains expressing wild-type BTH_I2138

  • Use appropriate statistical methods with biological replicates

This approach follows experimental design principles noted in search result : "A good experimental design requires a strong understanding of the system you are studying" and incorporates the recommendation to "systematically and precisely manipulate the independent variable(s)" while "precisely measuring the dependent variable(s)" .

The resulting data would provide detailed insights into how specific regions or residues of BTH_I2138 contribute to proper cell division in B. thailandensis, potentially revealing conserved mechanisms across bacterial species.

What Are the Methodological Considerations for Integrating Transcriptomic and Proteomic Approaches to Study BTH_I2138 Function?

Integrating transcriptomic and proteomic data provides a comprehensive view of BTH_I2138's function in cellular context:

• Experimental Design Considerations:

  Design Element	Recommendation	Rationale
  Comparison groups	Wild-type vs. ΔBTH_I2138 mutant	Direct assessment of BTH_I2138's impact
  Growth conditions	Multiple conditions (e.g., rich media, minimal media, stress)	Reveals condition-specific effects
  Time points	Multiple points during growth curve	Captures dynamic regulation
  Replication	Minimum 3 biological replicates	Ensures statistical robustness
  Controls	Include complemented strain	Confirms phenotypes are due to BTH_I2138

• Technical Approach:

  • Transcriptomics: "RNA sequencing (RNA-Seq) to identify differentially expressed genes"

  • Proteomics: "Mass spectrometry-based quantitative proteomics (e.g., iTRAQ, TMT, SILAC)"

  • Integration: "Correlation analysis between transcript and protein levels"

• Expected Outcomes and Interpretation:
  Based on previous B. thailandensis studies: "We identified 928 differentially expressed genes and 832 differentially expressed proteins" and "an only modest correlation between transcriptome and proteome changes was seen" . This suggests that:

  • Post-transcriptional regulation may be important for BTH_I2138 function

  • Protein-level changes may not always reflect transcript-level changes

  • Integrated analysis is essential for complete understanding

• Validation Approaches:

  • qRT-PCR for selected differentially expressed genes

  • Western blot for key protein changes

  • Phenotypic analysis of mutants in identified pathways

  • Protein-protein interaction studies for potential BTH_I2138 partners

This integrated approach aligns with modern systems biology practices and provides a more complete picture of BTH_I2138's role than either transcriptomics or proteomics alone, potentially revealing unexpected connections to other cellular processes and regulatory networks.

How Can Researchers Develop and Validate Specific Antibodies Against BTH_I2138?

Developing high-quality antibodies against BTH_I2138 is essential for many experimental applications:

• Antigen Design Strategy:

  Antigen Type	Advantages	Disadvantages	Design Considerations
  Full-length recombinant BTH_I2138	Complete epitope representation	Challenging expression, hydrophobicity	Use His-tag for purification, solubilize with appropriate detergents
  Synthetic peptides from hydrophilic regions	Easier production, target specific domains	Limited epitopes, may not recognize native protein	Select 15-20aa peptides from predicted extracellular loops
  Extracellular domain fragments	Balance between specificity and native structure	Expression challenges	Careful boundary selection to ensure proper folding

• Immunization Protocol Based on BipD Antibody Development:
  "The rBipD was obtained by affinity chromatography using His Trap column, then mixed with Fredrick's adjuvant to immunize BALB/c mice by intraperitoneal injection in order to obtain anti-rBipD polyclonal antibodies" . The protocol yielded high-titer antibodies (1:512,000).

  Adapted Protocol for BTH_I2138:

  • Purify recombinant His-tagged BTH_I2138 protein

  • Mix with Freund's complete adjuvant for initial immunization

  • Boost with antigen in Freund's incomplete adjuvant at days 14, 28, and 42

  • Collect serum and test antibody titer by ELISA

  • Purify IgG fraction using protein A/G columns

• Validation Strategy:

  Validation Test	Methodology	Acceptance Criteria
  Western blot against recombinant BTH_I2138	Standard Western blot protocol	Single band at expected MW (~20 kDa plus tag)
  Western blot against B. thailandensis lysates	Compare wild-type and ΔBTH_I2138 strains	Band present in wild-type, absent in knockout
  Immunofluorescence microscopy	Fixed B. thailandensis cells	Specific membrane localization pattern
  Cross-reactivity testing	Western blot against related Burkholderia species	Expected bands in species with homologous proteins
  Pre-immune serum control	All applications	No specific reactivity

• Application Optimization:

  • For Western blot: Determine optimal antibody dilution, blocking conditions

  • For immunoprecipitation: Test different lysis buffers, antibody amounts

  • For immunofluorescence: Optimize fixation method, permeabilization conditions

  • For ELISA: Establish standard curves, determine detection limits

Following these methodological steps will yield high-quality antibodies against BTH_I2138 that can be used to investigate its expression, localization, and interactions, significantly advancing research on this important cell division protein.