Gene Editing Using Lambda Phage (λ Phage)
1. Research Background
Lambda phage is one of the best-characterized temperate phages inthe history of molecular biology and serves as a cornerstone for studies onprokaryotic gene regulation, site-specific recombination, and transductiontechnologies. Its genome (approximately 48.5 kb) contains unique cos sitesand a sophisticated lysis–lysogeny switch, making it an ideal model insynthetic biology for constructing genetic circuits, vector systems, andinvestigating virus–host interactions.
Against this background, Shutong Bio provides customized genomeengineering services for Lambda phage. Using a CRISPR/Cas9-assistedselection system combined with the classic BRED (BacteriophageRecombineering of Electroporated DNA) technique, we enable highly efficientgene knockout, large-fragment insertion, point mutation, and functional elementintegration in the λ genome. We deliver strictly purified mutant phage strains.We are committed to providing professional and reliable Lambda phage geneediting solutions for global research clients.
2. Phage Characteristics and Biological Background
(1) Host Range
Lambda phage specifically infects Escherichia coli and is abenchmark for studying virus–host interactions in Gram-negative bacteria.
(2) Structural Features
It belongs to the family Siphoviridae, with a typicalicosahedral head and a non-contractile long tail. Its linear double-strandedDNA genome circularizes via the cos sites after entering the host cell.
(3) Research Value
The λ phage Red recombination system (Exo, Beta, Gam) has beenwidely developed as a universal tool for bacterial gene editing. Furtherengineering of λ phage itself can optimize the efficiency of these molecularbiology tools.
(4) Life Cycle
It exhibits two life states: lytic and lysogenic,making it a natural system for studying biological stability switches andenvironmental responses.
3. Reported Editing Strategies
Given the complex recombination mechanisms and high frequency ofspontaneous mutations in Lambda phage, the mainstream editing strategiescurrently used include:
3.1 CRISPR/Cas9 System (Mainstream Strategy)
(1) Principle: The Cas9 protein specifically cleaves theunmutated wild-type genome.
(2) Advantages: As a strong negative selection pressure, itcan improve recombination efficiency from extremely low levels in traditionalmethods to nearly 100%, enabling rapid and scarless genome engineering.
3.2 BRED Technology (Bacteriophage Recombineering)
Phage DNA and homologous DNA fragments containing mutationtemplates are co-introduced into host cells by electroporation, and editing isachieved using endogenous or exogenous recombinases.
3.3 In vitro Assembly & Rebooting
The genome is split into multiple modules, mutations are introducedvia methods such as Gibson assembly, and viral replication is then rebootedthrough an in vitro packaging system or electroporation.
4. Core Application Areas
(1) Molecular Tool Optimization: Modify genes related to theλ-Red system to improve recombination efficiency in Escherichia coli andother bacteria.
(2) Synthetic Biology Chassis: Integrate complex geneticlogic gates or reporter genes (e.g., lux, fluorescent proteins) into theλ genome to monitor environmental signals.
(3) Host Range Expansion: Engineer tail fiber proteins (Jprotein) to enable λ to recognize and infect non-standard E. colistrains or other closely related species.
(4) Novel Vector Development: Construct larger and morestable phage vectors for the construction and screening of large-scale genelibraries.
5. Project Workflow & Validation
We provide one-stop services from design to delivery to ensure theaccuracy of editing results:
(1) Design & Vector Construction: Designknockout/insertion vectors and sgRNAs for target sites.
(2) Transformation & Recombination Screening: Useoptimized electroporation conditions to overcome host transformation barriers.
(3) Targeted DNA Cleavage & Repair: Cleave the wild-typebackground with Cas9 to enrich positive clones.
(4) Multilevel Validation: Identify positive mutants andensure purity by single-plaque PCR and Sanger sequencing.
6. Gene Editing Project Introduction
6.1 Core Services
(1) Gene Knockout / Inactivation
Precise deletion of redundant genes or regulatory elements for thestudy of viral life cycle control.
(2) Gene Knock-in / Overexpression
Insertion of exogenous functional fragments into non-coding regionsor enhancement of endogenous promoter strength.
(3) Point Mutation / Scarless Modification
Accurate single-base substitution to study the thermostability orbinding affinity of key proteins (e.g., CI repressor).
(4) Multigene Sequential Editing
Simultaneous or stepwise modification of multiple loci in theLambda genome to construct highly customized engineered phages.
6.2 Technical Advantages
(1) Rapid Delivery: Standardized workflows ensure confirmedmutant phages are delivered in the shortest time.
(2) High-Efficiency Screening: Optimized CRISPR selectionsystem improves screening efficiency to over 80%.
7. Case Study
Case: In Situ Targeted Base Editing of Mouse Gut Bacteria
Project Description: Engineered λ phage particles are used todeliver base editors for efficient and precise gene editing of gut bacteria.
(1) Research Background
Microbiome studies have shown that specific gene expression in gutbacteria can directly affect host health, such as influencing immunotherapyefficacy, driving neurodegenerative diseases, or metabolizing drugs.
Although existing CRISPR tools enable efficient editing in humancells, technologies for in situ editing of gut bacteria remain limited.Traditional methods rely on editing after bacterial culture, which fails torecapitulate the complex intestinal environment and may carry risks oftransgene dissemination.
This study aims to develop a non-invasive strategy for precise genemodification of target bacteria directly in the mouse gut, providing a noveltool for microbiome functional research and therapeutic development.
(2) Project Design
The research team designed an engineered λ phage-based deliverysystem with the following key innovations:
Vector Engineering
Tail fiber (STF) and tail spike protein (gpJ) were modified toconstruct chimeric receptors (e.g., λ-P2 STF, λ-K5 STF) for targeting diversebacterial surface receptors (e.g., OmpC, capsular polysaccharide), therebyexpanding the host range.
Directed evolution was used to optimize gpJ variants (e.g., A8 and1A2), improving binding efficiency to highly expressed intestinal receptors(e.g., OmpC) and ensuring efficient delivery in complex environments.
Editing System Design
Adenine Base Editors (ABE8e) and Cytosine Base Editors (CBE) wereemployed to achieve precise point mutations without DNA double-strand breaks.
A non-replicative DNA vector was designed, which replicates only inproducer strains and is degraded after transient expression in target bacteria,avoiding transgene persistence and spread.
In Vitro and In Vivo Validation Platform
Editing efficiency was evaluated in in vitro models. Astreptomycin-treated mouse model was used to mimic the human gut environmentfor in situ editing tests.
3) Experimental Conclusions
High Editing Efficiency
In vitro, single-dose ABE achieved over 99.99% editing efficiencyfor the β-lactamase gene (bla). CBE exhibited 37%–92% efficiency forpathogenic genes including clbH and fimH. Low off-target effectswere confirmed by sequencing; Illumina sequencing showed that mutationfrequencies at candidate off-target sites were not significantly higher thanbackground error.
Stable In Vivo Editing
In mouse gut, a single dose (4×10¹⁰ particles) yielded a medianediting efficiency of 93% for the bla gene, and edited microbiotaremained stable for at least 42 days. Multi-dose treatment further increasedediting proportions (e.g., from 36% to 88%), with a positive correlationbetween dosage and editing efficacy.
Broad‑Spectrum Applicability
Virulence factors (e.g., csgA, cnf1) in pathogenicstrains including uropathogenic E. coli UTI89 and Klebsiellapneumoniae ST258 were successfully edited, demonstrating that thetechnology can be extended to diverse bacterial species.
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