Mechanistic and functional aspects of the Ruminococcin C sactipeptide isoforms.

Area of Science:

• Microbiology
• Biochemistry
• Drug Discovery

Background:

• Antibiotic resistance is a major public health concern, necessitating novel therapeutic strategies.
• Ribosomally synthesized and post-translationally modified peptides (sactipeptides) are a promising class of antimicrobial compounds.
• The Gram-positive human gut symbiont *Ruminococcus gnavus* E1 produces five sactipeptides, Ruminococcins C1-C5 (RumC1-C5).

Purpose of the Study:

• To adapt the biosynthesis protocol for mature RumC2-5 and evaluate their antibacterial activities.
• To assess the safety and multifunctionalities of all RumC isoforms.
• To identify key residues responsible for the antibacterial activity of RumC isoforms.

Main Methods:

• Biosynthesis of RumC2-5 using adapted protocols.
• Evaluation of antibacterial activity against multidrug-resistant Gram-positive clinical isolates.
• Assessment of synergistic effects with conventional antibiotics.
• Identification of crucial residues through structure-activity relationship studies.

Main Results:

• The biosynthesis protocol was successfully adapted for mature RumC2-5.
• All five RumC isoforms exhibited varying degrees of antibacterial efficacy against multidrug-resistant strains.
• All RumCs were found to be safe for human use and displayed multifunctionalities.
• Synergistic activity was observed between RumCs and cell wall-targeting antibiotics, but not among RumCs themselves.
• Crucial residues contributing to the antibacterial activity of RumC isoforms were identified.

Conclusions:

• Ruminococcins (RumCs) represent a viable alternative to combat antibiotic resistance.
• RumCs demonstrate safety, broad-spectrum activity, and synergistic potential with existing antibiotics.
• Further research into RumC structure-activity relationships can guide the development of novel antimicrobial agents.