Antimicrobial and quorum sensing interference of a cysteine- and arginine-deleted linear Tachyplesin analog (CRDT) against Staphylococcus aureus and Pseudomonas aeruginosa.

The rise of multidrug-resistant pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa has driven the search for novel antimicrobial agents with enhanced efficacy and reduced toxicity. Tachyplesin I (TP-I), a β-sheet antimicrobial peptide isolated from horseshoe crab hemocytes, is known for its broad-spectrum activity but is limited by the presence of cysteine-rich disulfide bonds. In this study, we evaluated two synthetic analogs: CDT (Cysteine-Deleted Tachyplesin I) and CRDT (Cysteine- and Arginine-Deleted Tachyplesin Analog), designed to simplify the structure and reduce production cost while maintaining or enhancing bioactivity. The antimicrobial efficacy of CDT and CRDT was assessed against S. aureus and P. aeruginosa through minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. CRDT demonstrated potent antimicrobial activity, with enhanced membrane-disruptive effects visualized via scanning electron microscopy (SEM), especially in P. aeruginosa. Molecular docking revealed strong binding affinities between CRDT and key QS regulators-SarA in S. aureus, and LasR in P. aeruginosa-supporting its ability to interfere with bacterial communication systems, while qRT-PCR analysis showed significant downregulation of QS-related genes (agrA, sarA, hla, algD and pelA). These findings suggest that CRDT not only exhibits direct bactericidal activity but also interferes with QS-mediated communication, making it a promising candidate for the development of dual-action antimicrobial therapeutics targeting both bacterial viability and virulence.