An acetoin-regulated expression system of Bacillus subtilis

Area of Science:

• Molecular Biology
• Microbial Biotechnology
• Gene Expression Systems

Background:

• Bacillus subtilis metabolizes acetoin, an overflow metabolite, in the early stationary phase.
• The acoABCL operon encodes the acetoin dehydrogenase complex, crucial for acetoin catabolism.
• The acoA promoter is repressed by glucose but induced by acetoin when glucose is depleted.

Purpose of the Study:

• To develop and characterize a novel gene expression system in Bacillus subtilis.
• To leverage the acoABCL operon promoter for controlled recombinant gene expression.
• To investigate conditions for sustained expression during nutrient limitation.

Main Methods:

• Construction and characterization of reporter gene fusions with the acoA promoter.
• Co-expression of the regulator gene acoR to enhance promoter activity.
• Analysis of promoter activity with different carbon sources and in ccpA mutant strains.

Main Results:

• The acoA promoter activity is strongly repressed by glucose and induced by acetoin.
• Co-expression of acoR significantly increased acoA promoter activity (more than twofold).
• The expression system functions with non-PTS sugars and in a ccpA mutant background.
• Expression levels correlate directly with the concentration of acetoin in the medium.

Conclusions:

• A robust Bacillus subtilis expression system based on the acoABCL operon promoter was established.
• This system enables sustained recombinant gene expression by utilizing acetoin as an alternative energy source during glucose limitation.
• The system's activity is tunable based on acetoin availability, offering a controllable platform for biotechnological applications.