A versatile mini-mazF-cassette for marker-free targeted genetic modification in Bacillus subtilis

Area of Science:

• Microbiology
• Molecular Biology
• Synthetic Biology

Background:

• Previous MazF-cassette systems for Bacillus subtilis genetic manipulation had limitations.
• These included cloning-dependent methods and poorly controlled gene expression.

Purpose of the Study:

• To develop an improved mini-MazF cassette for marker-free genetic manipulation in Bacillus subtilis.
• To overcome the drawbacks of previous methodologies, enhancing efficiency and control.

Main Methods:

• Modified the MazF cassette using a mini Zeocin resistance gene and a tightly controlled Bacillus subtilis xyl promoter.
• Applied the mini-MazF cassette for gene knockout (amyE), large gene cluster deletion (90-kb), and gene knock-in (GFP expression).
• Utilized a cloning-independent methodology with small PCR-fused fragments (2-2.5 kb) for repeated genetic modifications.

Main Results:

• Successfully performed marker-free gene knockout, deletion, and knock-in in Bacillus subtilis 1A751 without unwanted sequences.
• Demonstrated repeated use of the mini-MazF cassette for multiple gene/cluster deletions.
• Achieved nearly 100% desired clone generation frequency with reduced PCR-induced mutations.
• Observed a lower frequency of spontaneous mazF-resistant mutants.

Conclusions:

• The modified mini-MazF cassette offers significant improvements over existing methods for Bacillus subtilis genetic manipulation.
• The system is efficient, rapid (approx. 3 days), and applicable to other Bacillus species.
• Enables precise and versatile marker-free genome engineering in bacteria.