Three non-aspartate amino acid mutations in the ComA Response regulator receiver motif severely decrease surfactin...

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Bacillus subtilis produces bioactive peptides, including the lipopeptide surfactin, crucial for biosurfactant and antibiotic functions.
• Surfactin production is regulated by the srfA promoter and the ComP-ComA signal transduction system.
• Understanding ComA's role is vital for modulating Bacillus subtilis' biological activities.

Purpose of the Study:

• To investigate the impact of mutations in the ComA gene on surfactin production and biological activity in Bacillus subtilis.
• To elucidate the structural and functional consequences of ComA mutations.
• To explore the potential for ComA restoration to recover surfactin-related phenotypes.

Main Methods:

• Generation of Bacillus subtilis mutant strain Bs-M49 via low-energy ion implantation.
• Comparative analysis of surfactin production, antifungal activity, competence, and sporulation between wild-type and mutant strains.
• ComA gene sequencing, RT-PCR for gene expression analysis, ComA complementation, HPLC for surfactin quantification, and 3D protein structure prediction.

Main Results:

• The Bs-M49 mutant exhibited significantly reduced surfactin levels, diminished antifungal activity against R. solani, and altered competence and sporulation.
• Sequence analysis revealed three missense mutations in the comA gene of Bs-M49, affecting the ComA protein.
• Complementation of the comA gene in the Bs-M49 mutant restored hemolytic and antifungal activities, along with wild-type surfactin production levels.

Conclusions:

• The three identified missense mutations in the ComA protein critically impair Bacillus subtilis' biological activities, particularly surfactin production.
• ComA plays a pivotal role in regulating downstream gene expression, likely through phosphorylation-dependent conformational changes involving key N-terminal residues.
• Targeting ComA mutations offers a potential strategy for manipulating surfactin biosynthesis and associated phenotypes in Bacillus subtilis.