Recombinant Burkholderia cenocepacia Probable intracellular septation protein A (Bcen2424_1910)

What is Bcen2424_1910 and what is its predicted function in Burkholderia cenocepacia?

Bcen2424_1910 is a probable intracellular septation protein A from Burkholderia cenocepacia, consisting of 176 amino acids . Based on homology with septation proteins in other bacterial species, it likely participates in the divisome assembly during bacterial cell division. The septation process in bacteria involves the formation of a septum at mid-cell, which eventually leads to the separation of daughter cells. Similar to proteins described in other bacterial species, Bcen2424_1910 may function alongside components like FtsZ, FtsA, and other division proteins to facilitate proper septum formation . While the exact biochemical activities of Bcen2424_1910 remain to be fully characterized, its classification suggests a role in the coordination of septum synthesis and cell wall remodeling during division.

How is recombinant Bcen2424_1910 typically expressed and purified for research applications?

Recombinant Bcen2424_1910 is commonly expressed in E. coli expression systems with a histidine tag to facilitate purification . The full-length protein (amino acids 1-176) can be produced using standard molecular cloning techniques. The process typically involves:

• Amplification of the Bcen2424_1910 gene sequence from B. cenocepacia genomic DNA using PCR with specific primers

• Cloning into an appropriate expression vector containing a His-tag sequence

• Transformation into a suitable E. coli strain for protein expression

• Induction of protein expression using IPTG or similar inducers

• Cell lysis and protein extraction

• Purification using nickel-affinity chromatography, leveraging the His-tag

• Further purification steps may include size exclusion chromatography or ion exchange chromatography

• Confirmation of protein identity and purity using SDS-PAGE and Western blotting

This approach produces His-tagged recombinant Bcen2424_1910 protein suitable for functional assays, structural studies, and protein-protein interaction analyses .

What experimental approaches can be used to study Bcen2424_1910 localization in bacterial cells?

Several microscopy-based approaches can be employed to study the subcellular localization of Bcen2424_1910:

• Fluorescent Protein Fusion: Creating a genetic fusion of Bcen2424_1910 with fluorescent proteins like GFP or mCherry allows for real-time visualization in living cells. Care must be taken to ensure the fusion doesn't interfere with protein function.

• Immunofluorescence Microscopy: Using specific antibodies against Bcen2424_1910 followed by fluorescently-labeled secondary antibodies. This approach requires cell fixation and permeabilization.

• Co-localization Studies: Performing dual-labeling experiments with known divisome components like FtsZ to determine the spatiotemporal relationship between Bcen2424_1910 and other cell division proteins .

• Time-lapse Microscopy: Following the dynamic localization of Bcen2424_1910 throughout the cell cycle to determine when and where it assembles at the division site.

For optimal results, these approaches should be complemented with controls to verify specificity and functionality of the tagged protein. Based on studies of similar septation proteins, Bcen2424_1910 would likely exhibit mid-cell localization during the cell division process, coinciding with the formation of the Z-ring and recruitment of other divisome components .

How can insertional mutagenesis be optimized to study Bcen2424_1910 function in B. cenocepacia?

Insertional mutagenesis is a powerful approach for investigating the function of Bcen2424_1910 in B. cenocepacia. Based on established protocols, the following optimized methodology is recommended:

• Design and PCR-amplify an internal fragment (~300-400 bp) of the Bcen2424_1910 gene using forward and reverse primers with appropriate restriction enzyme sites .

• Digest both the PCR-amplified internal fragment and a suicide vector (such as pGPΩTp) with compatible restriction enzymes (XbaI and EcoRI have been successfully used for B. cenocepacia) .

• Ligate the digested fragment into the suicide vector and transform into an E. coli strain suitable for conjugation (e.g., E. coli SY327) .

• Introduce the resulting plasmid into B. cenocepacia K56-2 wild-type strain via triparental mating or electroporation.

• Select exconjugants on appropriate antibiotic-containing media (trimethoprim resistance has been used successfully) .

• Confirm insertion using colony PCR with a primer that anneals upstream of the 5' end of the internal fragment and a primer that anneals with the plasmid .

• Validate the disruption using RT-PCR or Western blotting to confirm the absence of functional Bcen2424_1910.

This approach creates a single crossover insertion that disrupts the target gene. To assess the resulting phenotype, compare growth rates, cell morphology, division dynamics, and susceptibility to various stresses between the mutant and wild-type strains. Since septation proteins are often essential, it may be necessary to create conditional mutants if complete gene disruption is lethal .

What approaches can be used to identify protein-protein interactions involving Bcen2424_1910 within the divisome complex?

To comprehensively map the protein-protein interactions of Bcen2424_1910 within the bacterial divisome, multiple complementary approaches should be employed:

• Bacterial Two-Hybrid System:

  • Clone Bcen2424_1910 into appropriate bacterial two-hybrid vectors

  • Screen against a library of known divisome components (FtsZ, FtsA, ZipA, FtsEX, FtsQLB, FtsW, FtsI)

  • Validate positive interactions with targeted tests

• Co-immunoprecipitation (Co-IP):

  • Express epitope-tagged Bcen2424_1910 in B. cenocepacia

  • Perform Co-IP using antibodies against the tag

  • Identify co-precipitating proteins via mass spectrometry

  • Confirm interactions with reciprocal Co-IP experiments

• Fluorescence Resonance Energy Transfer (FRET):

  • Create fusion proteins with appropriate fluorophore pairs

  • Measure FRET efficiency to detect direct interactions in vivo

  • Use time-lapse FRET to monitor dynamic interactions during cell division

• Pull-down Assays:

  • Use purified His-tagged Bcen2424_1910 as bait

  • Incubate with B. cenocepacia cell lysates

  • Identify interacting proteins by mass spectrometry

• Crosslinking Mass Spectrometry:

  • Apply protein crosslinking in vivo

  • Digest and analyze crosslinked peptides by mass spectrometry

  • Map interaction interfaces at amino acid resolution

Based on knowledge of bacterial cell division, Bcen2424_1910 likely interacts with components of the divisome machinery, possibly including FtsZ, FtsA, or proteins involved in peptidoglycan synthesis at the septum . The combination of these approaches provides a robust framework for mapping the interaction network of Bcen2424_1910.

How does the function of Bcen2424_1910 compare with homologous proteins in other bacterial species?

Comparative functional analysis of Bcen2424_1910 with homologous proteins in other bacterial species requires a multi-faceted approach:

• Sequence and Structural Comparison:

  • Perform multiple sequence alignment with homologs from diverse bacterial species

  • Identify conserved domains and motifs characteristic of septation proteins

  • Generate structural models using homology modeling and compare with known structures

  • Analyze conservation of key functional residues

• Complementation Studies:

  • Clone Bcen2424_1910 into expression vectors compatible with diverse bacterial hosts

  • Introduce into strains with mutations in homologous septation genes

  • Assess restoration of wild-type phenotypes in terms of:

    • Cell morphology

    • Division rate

    • Septum formation

    • Viability under various stress conditions

• Comparative Localization:

  • Express fluorescently tagged Bcen2424_1910 in heterologous hosts

  • Compare subcellular localization patterns with native homologs

  • Assess co-localization with known divisome components like FtsZ

For complementation studies in heterologous hosts, the pBKrhaB2 plasmid system, which has been successfully used for B. cenocepacia proteins, can be employed . This plasmid allows for rhamnose-inducible expression and has been shown to be effective for complementation experiments in Burkholderia species.

Based on studies of cell division in model organisms, if Bcen2424_1910 functions similarly to other septation proteins, it would likely complement mutations in homologous genes and exhibit similar localization patterns at the division septum .

What are the optimal experimental designs for investigating the role of Bcen2424_1910 in c-di-GMP signaling pathways?

Given the importance of c-di-GMP signaling in regulating various bacterial processes including biofilm formation and motility in B. cenocepacia, investigating potential connections with Bcen2424_1910 requires careful experimental design:

• Quantification of Intracellular c-di-GMP Levels:

  • Generate Bcen2424_1910 mutant and complemented strains

  • Grow bacterial cultures in SCFM medium for 24 hours

  • Extract nucleotides using the boiling/ethanol extraction method:

    • Standardize cultures to OD600 0.9

    • Wash cells in ice-cold H2O

    • Boil cells at 100°C for 10 min

    • Add ice-cold 65% ethanol

    • Centrifuge and collect supernatant

    • Dry extracts using vacuum centrifugation

    • Resuspend in water and filter (0.2 μm)

  • Quantify c-di-GMP using RP-HPLC

  • Compare levels between wild-type, mutant, and complemented strains

• Phenotypic Assays Related to c-di-GMP Signaling:

  • Biofilm formation using crystal violet staining

  • Swimming motility assays in soft agar

  • Swarming motility on semi-solid surfaces

  • Electron microscopy to examine cellular appendages

  • Congo red binding to assess exopolysaccharide production

• Protein-Protein Interaction Studies:

  • Test for interactions between Bcen2424_1910 and known c-di-GMP metabolizing enzymes (diguanylate cyclases and phosphodiesterases)

  • Investigate potential interactions with c-di-GMP binding proteins

  • Examine effects of c-di-GMP on Bcen2424_1910 localization and function

• Transcriptional Analysis:

  • Perform RNA-seq comparing wild-type and Bcen2424_1910 mutant strains

  • Focus on genes involved in c-di-GMP metabolism and c-di-GMP-regulated processes

  • Validate findings using qRT-PCR

  • Compare with known c-di-GMP regulons in B. cenocepacia

This comprehensive approach will help determine whether Bcen2424_1910 influences c-di-GMP signaling directly or indirectly, and whether its function is regulated by c-di-GMP levels.

What are the critical considerations for designing complementation experiments to confirm Bcen2424_1910 function?

Effective complementation experiments require careful consideration of several key factors:

• Vector Selection and Construction:

  • Choose an appropriate vector system such as pBKrhaB2, which has been successfully used for complementation in B. cenocepacia

  • Consider using a rhamnose-inducible promoter to control expression levels

  • Include the native promoter region if studying regulatory aspects

  • Ensure the vector has appropriate antibiotic resistance markers compatible with the mutant strain

• Cloning Strategy:

  • PCR-amplify the complete Bcen2424_1910 gene including its native ribosome binding site

  • Use appropriate restriction enzymes (e.g., NdeI and XbaI) for directional cloning

  • Verify the construct by sequencing to ensure no mutations were introduced during PCR

• Expression Level Control:

  • Titrate inducer concentration (e.g., rhamnose) to achieve near-physiological expression levels

  • Confirm expression levels by Western blotting or qRT-PCR

  • Consider potential polar effects on downstream genes

• Comprehensive Phenotypic Analysis:

  • Compare wild-type, mutant, and complemented strains across multiple phenotypes:

    • Growth kinetics in various media

    • Cell morphology and division patterns

    • Stress responses

    • Biofilm formation

    • Motility

    • Virulence in appropriate model systems

• Controls:

  • Include empty vector controls in the mutant background

  • Consider complementation with mutated versions of Bcen2424_1910 (point mutations in key residues) to identify critical functional domains

  • Use a heterologous gene known not to complement as a negative control

A well-designed complementation experiment should restore wild-type phenotypes in the Bcen2424_1910 mutant strain, confirming that the observed phenotypes are specifically due to the loss of Bcen2424_1910 function rather than polar effects or secondary mutations .

What advanced imaging techniques can provide insights into Bcen2424_1910 dynamics during bacterial cell division?

Advanced imaging techniques offer powerful approaches to visualize and analyze the dynamics of Bcen2424_1910 during the cell division process:

• Super-Resolution Microscopy:

  • Stimulated Emission Depletion (STED) microscopy

  • Photoactivated Localization Microscopy (PALM)

  • Stochastic Optical Reconstruction Microscopy (STORM)

  • Benefits: Overcome the diffraction limit to achieve ~20-50 nm resolution

  • Applications: Precisely localize Bcen2424_1910 relative to other divisome components

• Single-Molecule Tracking:

  • Label Bcen2424_1910 with photoactivatable fluorescent proteins

  • Track individual molecules to determine:

    • Diffusion rates in different cellular regions

    • Residence times at the division site

    • Binding/unbinding kinetics with other divisome components

  • Correlate with stages of FtsZ treadmilling and septum constriction

• Fluorescence Recovery After Photobleaching (FRAP):

  • Photobleach fluorescently-labeled Bcen2424_1910 at the septum

  • Measure recovery kinetics to determine:

    • Mobile vs. immobile fractions

    • Exchange rates with the cytoplasmic pool

    • Stability of association with the divisome

• Förster Resonance Energy Transfer (FRET):

  • Generate donor-acceptor pairs with Bcen2424_1910 and potential interaction partners

  • Measure FRET efficiency to determine:

    • Direct protein-protein interactions

    • Conformational changes during division

    • Temporal sequence of protein recruitment

• Cryo-Electron Tomography:

  • Visualize the native 3D architecture of the divisome

  • Localize Bcen2424_1910 using immunogold labeling

  • Determine spatial relationships within the division machinery at molecular resolution

These techniques should be combined with time-lapse imaging to correlate Bcen2424_1910 dynamics with specific stages of the division process. Based on studies of other septation proteins, Bcen2424_1910 might exhibit dynamic behavior similar to proteins that participate in the late stages of divisome assembly, potentially showing coordinated activity with proteins involved in peptidoglycan synthesis like FtsW and FtsI .

How should researchers interpret phenotypic data from Bcen2424_1910 mutant strains?

Interpreting phenotypic data from Bcen2424_1910 mutant strains requires careful consideration of multiple factors and potential confounding variables:

• Growth and Division Phenotypes:

  • Subtle changes in growth rates may indicate partial functional redundancy

  • Altered cell morphology (filamentation, mini-cells) suggests defects in septum positioning or formation

  • Changes in sensitivity to cell wall-targeting antibiotics may indicate altered peptidoglycan synthesis

• Distinguishing Direct from Indirect Effects:

  • Compare observed phenotypes with those of mutants affecting other divisome components

  • Use conditional mutants or depletion strains to distinguish primary defects from adaptive responses

  • Consider temporal progression of phenotypes after protein depletion

• Controlling for Genetic Background Effects:

  • Always compare mutant to the immediate parent strain

  • Generate multiple independent mutant clones to confirm consistency

  • Perform whole genome sequencing to identify potential secondary mutations

• Quantitative Analysis Approaches:

  • Cell size distribution analysis using automated image processing

  • Measurement of Z-ring dynamics and constriction rates

  • Quantification of peptidoglycan synthesis at the septum

  • Statistical analysis comparing multiple parameters between strains

• Experimental Conditions Considerations:

  • Test phenotypes under various growth conditions (rich vs. minimal media)

  • Examine effects of environmental stressors (osmotic stress, pH, temperature)

  • Consider growth phase-dependent effects (exponential vs. stationary)

• Interpretation Framework:

Carefully designed complementation experiments remain the gold standard for confirming that observed phenotypes are specifically due to the loss of Bcen2424_1910 function .

What bioinformatic approaches can predict functional domains and interacting partners of Bcen2424_1910?

A comprehensive bioinformatic analysis of Bcen2424_1910 can provide valuable insights into its functional domains and potential interaction partners:

• Sequence-Based Domain Prediction:

  • Search against domain databases (Pfam, SMART, CDD)

  • Identify transmembrane regions, signal peptides, and topology

  • Predict secondary structure elements

  • Analyze sequence conservation patterns across homologs

  • Identify potential functional motifs (e.g., peptidoglycan-binding domains)

• Structural Prediction and Analysis:

  • Generate 3D structural models using AlphaFold2 or RoseTTAFold

  • Validate models using quality assessment tools

  • Identify potential binding pockets or protein-protein interaction surfaces

  • Compare with structures of known septation proteins

  • Molecular dynamics simulations to predict flexible regions

• Prediction of Protein-Protein Interactions:

  • Co-evolution analysis to identify correlated mutations with potential partners

  • Genomic context analysis (gene neighborhood, fusion events, co-occurrence)

  • Text mining of scientific literature for reported interactions

  • Network-based approaches integrating multiple evidence types

• Functional Association Analysis:

  • Gene Ontology enrichment of predicted interactors

  • Pathway analysis to identify biological processes involving Bcen2424_1910

  • Comparison with protein interaction networks of known divisome components

  • Integration with transcriptomic data under relevant conditions

• Comparative Genomics Approaches:

  • Phylogenetic profiling to identify proteins with similar evolutionary patterns

  • Synteny analysis across bacterial genomes

  • Identification of species-specific adaptations vs. conserved functions

These bioinformatic approaches should be integrated to generate testable hypotheses about Bcen2424_1910 function and interactions, which can then be validated experimentally using the methods described in previous sections.

What emerging technologies could advance our understanding of Bcen2424_1910 function in bacterial cell division?

Several cutting-edge technologies hold promise for providing deeper insights into the function of Bcen2424_1910 and its role in bacterial cell division:

• CRISPR Interference (CRISPRi) Technology:

  • Enables precise and tunable repression of Bcen2424_1910 expression

  • Allows temporal control over gene silencing to study division dynamics

  • Can be multiplexed to simultaneously target multiple divisome components

  • Facilitates study of essential genes where complete knockout would be lethal

• Proximity-Dependent Biotinylation (BioID/TurboID):

  • Fusion of biotin ligase to Bcen2424_1910 to identify proximal proteins in vivo

  • Maps the protein interaction neighborhood in native conditions

  • Can capture transient interactions often missed by traditional approaches

  • Provides temporal resolution of interaction networks during division

• Native Mass Spectrometry:

  • Analyzes intact protein complexes to determine stoichiometry and composition

  • Preserves non-covalent interactions

  • Can detect ligand binding and conformational changes

  • Provides insights into the assembly of multi-protein complexes

• Microfluidics-Based Single-Cell Analysis:

  • Monitors single-cell division events with precise control of environment

  • Enables high-throughput phenotypic screening

  • Facilitates studies of cell-to-cell variability

  • Allows real-time manipulation of conditions during division

• Correlative Light and Electron Microscopy (CLEM):

  • Combines fluorescence localization of Bcen2424_1910 with ultrastructural context

  • Provides nanometer-resolution images of the division machinery

  • Allows visualization of protein localization relative to membrane and peptidoglycan remodeling

• Synthetic Cell Division Modules:

  • Reconstitution of minimal divisome components in liposomes

  • Systematic testing of Bcen2424_1910 contribution to division processes

  • Engineering of orthogonal division systems to probe fundamental mechanisms

These emerging technologies, when applied to the study of Bcen2424_1910, have the potential to resolve current knowledge gaps regarding its precise function within the bacterial divisome, its regulation, and its contributions to the mechanical and biochemical aspects of bacterial cell division .