Marine-Inspired Antimicrobial Peptides Disrupt Gene Expression at the DNA Level.

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Antimicrobial peptides (AMPs) are crucial in innate immunity.
• Existing AMPs often exhibit membrane-lytic activity, raising concerns about resistance and toxicity.
• Novel AMPs with distinct mechanisms are needed to combat rising antimicrobial resistance.

Purpose of the Study:

• To elucidate the mode of action of two novel antimicrobial peptides, L3 and L3-K, derived from *Streptomyces* sp. H-KF8.
• To investigate the molecular targets and cellular processes affected by L3 and L3-K in *Escherichia coli*.
• To assess the potential of these peptides as scaffolds for next-generation antimicrobial agents.

Main Methods:

• Tandem mass tag (TMT)-based quantitative proteomics to analyze proteome changes.
• Fluorescent dye displacement assays to assess DNA binding.
• In vitro transcription/translation assays to evaluate interference with central information processing.
• Minimum inhibitory concentration (MIC) determination.

Main Results:

• L3 and L3-K treatment resulted in significant proteome remodeling, affecting metabolism, transport, RNA processing, and cell structure.
• Both peptides disrupted ABC transporter function and induced stress responses.
• L3 and L3-K demonstrated nonspecific DNA binding, inhibiting transcription and translation, with inhibitory concentrations correlating with MICs.
• L3 specifically perturbed the *mal* regulon, indicating broader transcriptional dysregulation.

Conclusions:

• L3 and L3-K primarily exert their antimicrobial activity by targeting bacterial DNA and interfering with transcription and translation machinery.
• These peptides represent a promising class of non-membrane-lytic antimicrobial agents.
• L3 and L3-K can serve as valuable scaffolds for developing novel antimicrobial peptides with DNA-binding capabilities.