Clostridia DNA Integration via dcm- Methylation and Plasmid Vectors
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Solution Overview
Problem
Clostridia bacteria are recalcitrant to genetic manipulation due to their potent restriction-modification systems, making it difficult to achieve stable integration of foreign DNA and gene knockout via homologous recombination, with existing methods being complex and inefficient.
Innovation Solution
Using a dcm− bacterium to prepare a nucleic acid molecule with a sequence of interest and a selection marker, which is then propagated, isolated, and transformed into the target bacteria, allowing for stable integration by evading the host's restriction system and increasing the chances of homologous recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional transformation methods are used with Clostridia bacteria, then the restriction-modification system protects the bacteria from foreign DNA, but this results in very low transformation efficiency and difficulty in stable integration
Solution Approach 1:
The patent applies preliminary action by pre-methylating the transforming DNA with a phage methyltransferase before electroporation into Clostridia. This advance modification protects the foreign DNA from digestion by the bacterial restriction system, enabling successful transformation. The methyl groups are added beforehand to the DNA molecules, creating a protective mark that the restriction endonucleases cannot recognize or cut.
2Reliability
If DNA is methylated prior to transformation, then protection from restriction digestion is achieved, but transformation efficiency remains very low and stable integration is difficult
Solution Approach 1:
The patent uses a plasmid vector as an intermediary carrier to deliver the methylated DNA into Clostridia. The plasmid serves as a mediator that facilitates the introduction of foreign DNA, providing a replicable and selectable system. The plasmid contains origin of replication sequences and selection markers that enable efficient maintenance and selection of transformed cells, making gene knockout much easier despite the presence of restriction systems.
3Adaptability or versatility
If non-replicative plasmids or linear DNA are used for gene knockout, then homologous recombination can occur, but the process is very tedious and transformation efficiency is low
Solution Approach 1:
The patent employs a universal plasmid vector system that combines multiple functions: it carries the gene of interest, provides origin of replication for autonomous maintenance, includes selection markers for easy identification of transformants, and contains homologous regions for recombination-mediated integration. This multi-functional plasmid eliminates the need for separate preparation of linear DNA fragments and simplifies the entire gene knockout process into a single transformation step.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables efficient and stable integration of nucleic acid sequences into Clostridia bacteria, improving transformation efficiency and facilitating targeted gene disruption, as demonstrated by increased solvent production in mutant strains.
Implementation Method 1
The presence of a restriction-modification (RM) system represents a barrier for the transformation of bacteria with recombinant DNA. This is especially applicable to Clostridia sp. The recalcitrance of Clostridia to accept foreign DNA is caused by the presence of a potent restriction system, especially the type II restriction endonucleases.
Implementation Method 2
gene knockout via homologous recombination mechanisms using non-replicative plasmids or linear DNA was very tedious to achieve
Data Source
AI summary
The invention provides methods of preparing bacteria of interest with a stably integrated nucleic acid sequence of interest.