Recombinant Koribacter versatilis Undecaprenyl-diphosphatase (uppP)

What is the function of Undecaprenyl-diphosphatase (UppP) in bacterial cell wall synthesis?

Undecaprenyl-diphosphatase (UppP) catalyzes the critical dephosphorylation of undecaprenyl pyrophosphate (UPP) to undecaprenyl phosphate (UP), an essential carrier lipid in bacterial cell wall synthesis. This 55-carbon isoprenoid carrier functions as a universal transporter that ferries glycans and glycopolymers across the cytoplasmic membrane, including peptidoglycan precursors, O-antigen, capsule components, wall teichoic acids, and various sugar modifications . The dephosphorylation reaction catalyzed by UppP is indispensable for recycling the carrier lipid, ensuring its availability for continuous rounds of cell wall synthesis. In bacteria such as Bacillus subtilis, this reaction represents a bottleneck in the lipid II cycle, directly affecting cell wall homeostasis and integrity .

How does Koribacter versatilis UppP compare structurally to other bacterial UPP phosphatases?

While the specific structure of Koribacter versatilis UppP has not been extensively characterized in the provided research, comparative analysis with homologous proteins suggests it likely shares key structural features with other bacterial UPP phosphatases. K. versatilis, a member of the Acidobacteriota phylum, possesses a circular chromosome with 5,650,368 nucleotides encoding 4,777 proteins . Based on studies of UPP phosphatases in other bacteria, particularly Bacillus subtilis, K. versatilis UppP likely belongs to a distinct phosphatase family separate from the PAP2 phosphatases (such as BcrC in B. subtilis). The protein presumably contains transmembrane domains and conserved catalytic residues necessary for its phosphatase activity. Structural prediction using homology modeling would be required to definitively identify unique features that may distinguish K. versatilis UppP from its counterparts in other bacterial species.

What are the typical expression patterns of uppP genes in Koribacter versatilis?

Though specific expression data for uppP in Koribacter versatilis is limited in the available research, insights can be drawn from related bacteria. In Bacillus subtilis, the uppP gene (also known as yubB) shows expression levels comparable to bcrC during exponential growth, with approximately three-fold higher expression during stationary phase . Unlike bcrC, uppP expression in B. subtilis is not significantly induced by cell envelope stress conditions such as exposure to bacitracin . Considering K. versatilis's environmental niche as a soil bacterium with relatively slow growth rates (sometimes taking up to a week to form visible colonies), it's reasonable to hypothesize that uppP expression might be constitutive but regulated in response to growth phases and environmental conditions . Research using transcriptomic approaches would be necessary to precisely characterize uppP expression patterns in K. versatilis under various growth conditions.

What are the optimal conditions for heterologous expression of recombinant K. versatilis UppP?

For heterologous expression of recombinant Koribacter versatilis UppP, researchers should consider the following protocol based on the unique properties of both the organism and the enzyme:

Expression System Selection:

• E. coli BL21(DE3) or C43(DE3) strains are recommended for membrane protein expression

• Consider codon optimization for K. versatilis genes, as this slow-growing soil bacterium may have codon usage patterns divergent from common expression hosts

Vector Design:

• Use pET vectors with N-terminal His6-tag or C-terminal Strep-tag

• Include a TEV protease cleavage site for tag removal

• Consider fusion partners (e.g., MBP) to enhance solubility

Expression Conditions:

• Growth temperature: 18-20°C after induction to minimize inclusion body formation

• Inducer concentration: 0.1-0.5 mM IPTG

• Post-induction time: 16-20 hours

• Medium: Terrific Broth supplemented with 1% glucose

Membrane Protein Considerations:

• Supplement with 10 mM MgCl₂ to stabilize membrane fractions

• Consider autoinduction media to achieve higher cell densities before protein expression

These conditions should be systematically optimized through small-scale expression trials analyzing variables including temperature, inducer concentration, and expression time to maximize functional protein yield.

What purification strategy yields the highest activity for recombinant K. versatilis UppP?

A comprehensive purification strategy for recombinant K. versatilis UppP should address the challenges associated with membrane protein purification while preserving enzymatic activity:

Membrane Isolation:

• Harvest cells and resuspend in buffer containing 50 mM Tris-HCl pH 7.5, 300 mM NaCl, 10% glycerol, 1 mM DTT, and protease inhibitors

• Disrupt cells via sonication or French press (20,000 psi, 3 passes)

• Remove debris by centrifugation (10,000 × g, 20 min, 4°C)

• Ultracentrifuge supernatant (150,000 × g, 1 h, 4°C) to isolate membrane fraction

Solubilization:

• Resuspend membrane pellet in solubilization buffer containing 50 mM Tris-HCl pH 7.5, 300 mM NaCl, 10% glycerol, and detergent

• Optimal detergents include:

  • n-Dodecyl-β-D-maltopyranoside (DDM): 1%

  • n-Decyl-β-D-maltopyranoside (DM): 1%

  • Lauryl maltose neopentyl glycol (LMNG): 0.5%

• Incubate with gentle rotation for 2 hours at 4°C

• Ultracentrifuge (150,000 × g, a1 h, 4°C) to remove insoluble material

Affinity Chromatography:

• Load solubilized protein onto Ni-NTA or Strep-Tactin column

• Wash with 10-15 column volumes of wash buffer containing 50 mM Tris-HCl pH 7.5, 300 mM NaCl, 0.05% detergent, and 20 mM imidazole (for His-tag)

• Elute with buffer containing 250 mM imidazole (for His-tag) or 2.5 mM desthiobiotin (for Strep-tag)

Size Exclusion Chromatography:

• Apply concentrated protein to Superdex 200 column

• Elute with buffer containing 25 mM Tris-HCl pH 7.5, 150 mM NaCl, and 0.03% detergent

Throughout purification, maintain 5-10 mM MgCl₂ in all buffers as divalent cations are often essential for phosphatase activity. This strategy typically yields 1-3 mg of purified protein per liter of bacterial culture with preserved enzymatic activity.

What methods are reliable for measuring UppP activity in vitro?

Several complementary methods can be employed to reliably measure UppP activity in vitro:

Malachite Green Phosphate Assay:

• Principle: Detects released inorganic phosphate from UPP dephosphorylation

• Procedure:

  • Prepare reaction mixture containing 50 mM Tris-HCl pH 7.5, 10 mM MgCl₂, 0.1% Triton X-100, and 50-100 μM UPP substrate

  • Add purified UppP (1-5 μg) to initiate reaction

  • Incubate at 37°C for 5-30 minutes

  • Stop reaction with malachite green reagent

  • Measure absorbance at 630 nm

• Advantages: High sensitivity (nanomolar range), amenable to high-throughput screening

• Limitations: Potential interference from buffer components containing phosphate

Thin Layer Chromatography (TLC):

• Principle: Separates substrate (UPP) from product (UP) based on differential migration

• Procedure:

  • Perform enzyme reaction with radiolabeled [³²P]-UPP

  • Extract lipids using chloroform:methanol (2:1)

  • Spot on silica TLC plates

  • Develop using chloroform:methanol:water:ammonium hydroxide (65:25:4:0.5)

  • Visualize by autoradiography

• Advantages: Direct visualization of substrate-product conversion

• Limitations: Requires radioactive materials, lower throughput

Coupled Enzyme Assay:

• Principle: Couples phosphate release to NADH oxidation via enzymatic reactions

• Procedure:

  • Reaction mixture contains UppP, UPP, purine nucleoside phosphorylase, and 2-amino-6-mercapto-7-methylpurine ribonucleoside

  • Released phosphate triggers conversion of MESG to ribose-1-phosphate and 2-amino-6-mercapto-7-methylpurine

  • Monitor absorbance decrease at 360 nm

• Advantages: Continuous monitoring, high sensitivity

• Limitations: Potential interference from coupling enzymes

LC-MS/MS Analysis:

• Principle: Direct quantification of UPP and UP by mass spectrometry

• Procedure:

  • Extract lipids after enzyme reaction

  • Analyze by reverse-phase HPLC coupled to mass spectrometry

  • Quantify substrate depletion and product formation

• Advantages: Highly specific, can detect multiple reaction intermediates

• Limitations: Requires specialized equipment, lower throughput

A combination of these methods is recommended for comprehensive characterization of K. versatilis UppP activity.

How does the function of K. versatilis UppP differ from UppP homologs in other bacterial species?

The function of K. versatilis UppP likely exhibits distinctive characteristics compared to homologs in other bacterial species, reflecting adaptation to its unique ecological niche. While direct experimental evidence is limited, comparative analysis suggests several potential functional differences:

Substrate Specificity and Kinetics:
K. versatilis inhabits acidic soil environments where pH and mineral composition differ significantly from the habitats of model organisms like E. coli or B. subtilis. Its UppP may demonstrate:

• Optimized activity at acidic pH ranges (pH 4.5-6.0)

• Different metal ion preferences for catalysis (potentially Fe³⁺-dependent given K. versatilis's requirement for iron)

• Modified kinetic parameters (Km, kcat) reflecting adaptation to slower growth rates

Regulatory Mechanisms:
Unlike B. subtilis, where uppP expression remains relatively stable during cell envelope stress , K. versatilis UppP may be regulated differently:

• Potential integration with stress response systems specific to acidobacteria

• Different transcriptional control mechanisms reflecting its environmental exposures

• Possible post-translational modifications unique to K. versatilis

Physiological Role:
In B. subtilis, UppP works alongside BcrC with partial functional redundancy, with UppP being particularly crucial for sporulation . K. versatilis has not been documented to form spores, suggesting its UppP might have evolved:

• Greater importance in vegetative growth

• Specialized functions in cell wall modifications required for survival in acidic soils

• Possible involvement in cell wall adaptations related to K. versatilis's role in carbon cycling

Structural Distinctions:
Computational modeling based on sequence homology predicts potential structural differences in K. versatilis UppP:

• Modified transmembrane topology adapted to the unique membrane composition of Acidobacteriota

• Different substrate binding pocket architecture

• Potentially unique regulatory domains or protein-protein interaction surfaces

Experimental approaches combining heterologous expression, mutagenesis, and comparative biochemistry would be necessary to fully elucidate these functional differences.

What is the role of K. versatilis UppP in antibiotic resistance mechanisms?

While direct evidence for K. versatilis UppP's role in antibiotic resistance is not explicitly detailed in the provided research, several hypotheses can be proposed based on knowledge of UPP phosphatases in other bacteria:

Potential Direct Resistance Mechanisms:

• Bacitracin Resistance: UPP phosphatases are known to contribute to bacitracin resistance by reducing the pool of UPP (bacitracin's target) through accelerated conversion to UP. In B. subtilis, increased expression of bcrC (but not uppP) provides protection against bacitracin . K. versatilis UppP might similarly contribute to intrinsic bacitracin resistance, particularly significant given its soil habitat where Bacillus species producing bacitracin are common.

• Glycopeptide Antibiotic Interactions: Recent antibiotic discovery efforts have focused on compounds that bind lipid-linked precursors to deplete the universal carrier lipid undecaprenyl-phosphate . K. versatilis UppP may provide resistance against such compounds by maintaining adequate UP levels despite antibiotic challenge.

• Cell Wall Stress Response Integration: In B. subtilis, UPP phosphatases are integrated with the cell envelope stress response (CESR) system, with bcrC being induced by the σᴹ stress response . K. versatilis likely possesses analogous stress response systems that might upregulate UppP activity during antibiotic exposure.

Experimental Approaches to Investigate Resistance Functions:

• Heterologous expression studies in model organisms lacking UPP phosphatases

• Minimum inhibitory concentration (MIC) determinations with various antibiotics

• Transcriptomic analysis of K. versatilis under antibiotic challenge

• In vitro assays testing direct interactions between antibiotics and purified UppP

The slow growth rate of K. versatilis (up to a week for visible colonies) might contribute to intrinsic antibiotic resistance by reducing the impact of cell wall synthesis inhibitors that are most effective against rapidly dividing cells. The UppP enzyme may have evolved specific properties to maintain cell wall integrity under these slow growth conditions.

What are common challenges in expressing and purifying functional recombinant K. versatilis UppP?

Researchers working with recombinant K. versatilis UppP frequently encounter several challenges during expression and purification, which can be addressed through specific troubleshooting strategies:

Challenge 1: Low Expression Yields

• Cause: Codon bias discrepancies between K. versatilis and expression hosts

• Solution: Employ codon-optimized synthetic genes for the expression host (typically E. coli)

• Implementation: Analyze the codon adaptation index (CAI) and optimize rare codons, particularly for the first 50-100 nucleotides of the coding sequence

Challenge 2: Protein Misfolding and Inclusion Body Formation

• Cause: Membrane proteins often misfold when overexpressed

• Solution: Modify expression conditions and consider fusion partners

• Implementation:

  • Reduce induction temperature to 16-18°C

  • Decrease IPTG concentration to 0.1 mM

  • Add 5% glycerol to culture medium

  • Consider fusion with MBP or SUMO proteins

Challenge 3: Inactive Enzyme After Purification

• Cause: Loss of essential lipid interactions or cofactors during purification

• Solution: Optimize detergent selection and maintain cofactors

• Implementation:

  • Screen multiple detergents (DDM, LMNG, DMNG)

  • Maintain 5-10 mM MgCl₂ throughout purification

  • Consider lipid supplementation (E. coli lipid extract at 0.01-0.05 mg/ml)

Challenge 4: Protein Aggregation During Concentration

• Cause: Detergent concentration increase during protein concentration

• Solution: Careful detergent management during concentration steps

• Implementation:

  • Use concentration devices with higher molecular weight cut-offs (50-100 kDa)

  • Add fresh detergent at CMC during concentration

  • Consider alternative concentration methods like precipitation and resolubilization

Challenge 5: Inconsistent Activity Measurements

• Cause: Variability in substrate preparation and enzyme stability

• Solution: Standardize reagents and assay conditions

• Implementation:

  • Prepare UPP substrate stocks in small aliquots with consistent sonication protocol

  • Include internal standards in activity assays

  • Perform activity measurements immediately after purification

A systematic approach to addressing these challenges significantly improves the likelihood of obtaining functionally active K. versatilis UppP for subsequent biochemical and structural studies.

How can researchers distinguish the activity of UppP from other phosphatases in cellular extracts?

Distinguishing UppP activity from other phosphatases in cellular extracts requires specialized approaches that exploit the unique properties of this enzyme:

Substrate Specificity-Based Methods:

• Differential Inhibition Profile:

  • Treat extracts with phosphatase inhibitors with varying specificities:

    • Sodium orthovanadate (1 mM): inhibits tyrosine and alkaline phosphatases

    • Okadaic acid (100 nM): inhibits PP1 and PP2A serine/threonine phosphatases

    • Fluoride (50 mM): inhibits acid phosphatases

  • UppP activity is relatively resistant to these classical inhibitors

• Detergent Dependency:

  • UppP requires detergent for optimal activity due to its membrane-associated nature

  • Assay phosphatase activity with and without 0.1% Triton X-100 or DDM

  • UppP activity increases significantly with detergent while many cytosolic phosphatases show reduced activity

• Bacitracin Sensitivity:

  • UppP activity against UPP is inhibited by bacitracin (50-100 μg/ml)

  • Measure phosphatase activity with and without bacitracin

  • Bacitracin-sensitive component represents UPP phosphatase activity

Analytical Separation Techniques:

• Fractionation Approach:

  Fraction	Preparation Method	Expected UppP Activity
  Cytosolic	100,000×g supernatant	Minimal
  Membrane	100,000×g pellet, detergent-solubilized	High
  Periplasmic	Osmotic shock extraction	Minimal
  Cell wall	SDS-boiling of pellet after membrane extraction	None

• Ion Exchange Chromatography:

  • Apply detergent-solubilized membrane fractions to anion exchange column

  • Elute with NaCl gradient (0-500 mM)

  • Collect fractions and assay for phosphatase activity using UPP

  • UppP typically elutes at distinct NaCl concentration from other phosphatases

Molecular Biology Approaches:

• Immunodepletion:

  • Generate antibodies against recombinant K. versatilis UppP

  • Perform immunoprecipitation to deplete UppP from extracts

  • Compare phosphatase activity before and after immunodepletion

• Genetic Complementation:

  • Express K. versatilis UppP in uppP-deficient bacteria

  • Measure restored UPP phosphatase activity

  • Confirms specificity of the enzyme for UPP substrate

These complementary approaches provide researchers with robust methods to distinguish UppP activity from other phosphatases, essential for accurate characterization of this enzyme.

What strategies can overcome the challenges of working with K. versatilis, given its slow growth rate?

Koribacter versatilis presents unique challenges for researchers due to its extremely slow growth rate, sometimes requiring up to a week to form visible colonies . Several innovative strategies can overcome these limitations:

Heterologous Expression Systems:

• Advantage: Bypasses the need to culture K. versatilis directly

• Implementation:

  • Clone the uppP gene from K. versatilis genomic DNA

  • Express in rapid-growing hosts (E. coli, B. subtilis)

  • Validate function through complementation of uppP-deficient strains

  • Optimize expression using codon-harmonized sequences

• Limitation: May not capture native regulation and post-translational modifications

Culture Optimization for Native K. versatilis:

• Advantage: Preserves natural context of UppP expression

• Implementation:

  • Develop specialized media mimicking soil conditions:

    • pH 4.5-5.5

    • Supplemented with micronutrients, particularly iron compounds

    • Include humic substances (0.01-0.05%)

  • Employ microfluidic cultivation techniques for monitoring single cells

  • Use extended incubation periods (2-3 weeks) at 25-28°C

  • Consider co-culture with helper strains producing growth factors

• Limitation: Still significantly slower than model organisms

Cell-Free Expression Systems:

• Advantage: Rapid protein production without cell cultivation

• Implementation:

  • Develop cell extracts from E. coli or wheat germ

  • Add specialized lipids and cofactors required for UppP activity

  • Express K. versatilis UppP using optimized templates

  • Directly assay function in the cell-free reaction

• Limitation: May require optimization for membrane protein expression

Genomic and Bioinformatic Approaches:

• Advantage: Minimal reliance on cultivating the organism

• Implementation:

  • Analyze the K. versatilis genome sequence for uppP homologs

  • Perform comparative genomics with related bacterial species

  • Identify conserved regions and predict functional domains

  • Model protein structure using homology-based approaches

• Limitation: Requires experimental validation of predictions

Metatranscriptomic Studies:

• Advantage: Captures gene expression in natural environments

• Implementation:

  • Extract total RNA from soil samples known to contain K. versatilis

  • Enrich for K. versatilis transcripts using specific probes

  • Sequence and analyze uppP expression under various environmental conditions

  • Correlate expression with environmental parameters

• Limitation: Complex sample preparation and data analysis

By combining these approaches, researchers can overcome the growth limitations of K. versatilis while still gaining valuable insights into the function and properties of its UppP enzyme.

What are promising approaches for structural determination of K. versatilis UppP?

Structural determination of Koribacter versatilis UppP presents both challenges and opportunities. The following approaches offer promising pathways toward elucidating its three-dimensional structure:

X-ray Crystallography:

• Strategy: Lipidic cubic phase (LCP) crystallization

• Implementation:

  • Purify K. versatilis UppP with stability-enhancing mutations (e.g., thermostabilization through disulfide engineering)

  • Reconstitute in monoolein or related lipids at 40-60% (w/w)

  • Screen crystallization conditions focusing on pH 4.5-6.5 (matching K. versatilis natural environment)

  • Utilize microcrystallization techniques with specialized screening suites for membrane proteins

  • Collect diffraction data at synchrotron microfocus beamlines

• Expected Resolution: 2.0-3.5 Å

• Advantages: High-resolution details of active site architecture

• Challenges: Difficulty obtaining well-diffracting crystals of membrane proteins

Cryo-Electron Microscopy (Cryo-EM):

• Strategy: Single-particle analysis of detergent-solubilized or nanodisc-embedded UppP

• Implementation:

  • Purify K. versatilis UppP at high concentration (>5 mg/ml)

  • Consider reconstruction approaches:

    • Standard single-particle analysis (may be challenging due to small size)

    • Reconstitution into nanodiscs to increase effective molecular size

    • Attachment to Fab fragments to provide additional mass for alignment

  • Utilize latest-generation electron microscopes with energy filters

  • Employ motion correction and CTF estimation software

• Expected Resolution: 3.0-4.5 Å

• Advantages: No crystallization required; potential visualization of different conformational states

• Challenges: Small size of UppP (~30 kDa) makes particle alignment difficult

NMR Spectroscopy:

• Strategy: Solution NMR with selective isotopic labeling

• Implementation:

  • Express K. versatilis UppP with ¹⁵N, ¹³C, and selective ²H labeling

  • Purify in detergent micelles optimized for NMR (e.g., DPC, LPPG)

  • Perform TROSY-based experiments for backbone assignment

  • Utilize paramagnetic relaxation enhancement (PRE) to define topology

  • Collect residual dipolar coupling (RDC) data for refinement

• Expected Resolution: Atomic-level information for key regions

• Advantages: Dynamic information; potential for studying substrate interactions

• Challenges: Signal overlap; size limitations for complete structure determination

Integrative Structural Biology Approaches:

Each of these approaches offers unique advantages, and a combination of methods would likely yield the most comprehensive structural understanding of K. versatilis UppP.

How might the study of K. versatilis UppP contribute to antibiotic development?

The study of Koribacter versatilis UppP offers several promising avenues for antibiotic development that could address the growing challenge of antimicrobial resistance:

Novel Target Identification:
Koribacter versatilis represents an understudied bacterial phylum (Acidobacteriota) that constitutes up to 14% of soil bacterial communities . Structural and functional characterization of its UppP could reveal unique features that differentiate it from homologs in pathogenic bacteria, potentially leading to:

• Identification of druggable pockets specific to pathogen UppP enzymes

• Discovery of natural inhibitor compounds produced by K. versatilis as competitive advantage

• Understanding of resistance mechanisms that could be circumvented in drug design

Lipid II Cycle Vulnerability Mapping:
Research has shown that UPP phosphatases like BcrC and UppP form a synthetic lethal gene pair in B. subtilis . Similar studies with K. versatilis UppP could:

• Identify critical residues that could be targeted by combination therapeutics

• Map the vulnerability landscape of the lipid II cycle

• Reveal potential synergies between UppP inhibitors and existing antibiotics

Structural Scaffold for Rational Drug Design:
Structural determination of K. versatilis UppP would provide valuable templates for:

• Structure-based virtual screening against pathogen homologs

• Fragment-based drug discovery targeting the active site

• Design of transition-state analogs specific to the UPP dephosphorylation reaction

Resistance Mechanism Insights:
Recent research indicates that UPP phosphatases contribute to bacterial resilience against antibiotics targeting cell wall synthesis . Studying K. versatilis UppP could:

• Elucidate novel resistance mechanisms

• Identify ways to overcome existing resistance

• Develop inhibitors that block both enzyme activity and resistance development

Potential Drug Development Pathway:

The unique ecological niche of K. versatilis in acidic soils suggests it may produce or be resistant to natural products with antimicrobial activity, making it a promising source for novel antibiotic discovery. Additionally, understanding how this slow-growing bacterium maintains cell wall homeostasis could reveal new strategies for targeting metabolically quiescent bacterial populations that are often refractory to conventional antibiotics.

What research questions remain unanswered regarding the role of UppP in bacterial cell wall synthesis?

Despite advances in understanding UPP phosphatases, significant knowledge gaps remain regarding UppP's role in bacterial cell wall synthesis, particularly in non-model organisms like Koribacter versatilis:

Evolutionary and Comparative Biology Questions:

• How do UppP enzymes from different bacterial phyla compare in terms of structure, substrate specificity, and regulation?

• What evolutionary pressures have shaped UppP diversity across bacterial species, particularly in specialized environments like the acidic soils inhabited by K. versatilis?

• How has UppP co-evolved with other enzymes in the cell wall synthesis pathway to optimize lipid carrier recycling in different bacterial lineages?

Regulatory Mechanisms:

• How is uppP gene expression regulated in K. versatilis compared to model organisms like B. subtilis?

• What environmental triggers modulate UppP activity in soil bacteria, and how does this compare to pathogens?

• Is K. versatilis UppP regulated post-translationally through modifications or protein-protein interactions?

Structural and Mechanistic Inquiries:

• What are the molecular determinants of UppP substrate specificity and catalytic efficiency?

• How does the three-dimensional structure of K. versatilis UppP compare to known structures from other bacteria?

• What conformational changes occur during substrate binding and catalysis?

Systems Biology Perspectives:

• How does UppP activity influence global cell wall homeostasis and the distribution of undecaprenyl-phosphate between competing pathways?

• What is the quantitative contribution of UppP to undecaprenyl-phosphate recycling compared to de novo synthesis?

• How do bacteria balance UppP activity with other phosphatases in response to environmental stresses?

Experimental Approaches to Address These Questions:

These research questions represent fertile ground for future investigations, with potential implications for understanding bacterial cell wall biosynthesis across diverse species and environments. The unique properties of K. versatilis, including its ecological niche, slow growth rate, and phylogenetic position, make its UppP an intriguing subject for comparative studies that could reveal novel aspects of bacterial cell wall synthesis regulation.