Functional and expression characteristics identification of Phormicins, novel AMPs from Musca domestica with anti-MRSA biofilm activity, in response to different stimuli

Antibiotic-resistant bacteria (including MRSA) in the clinic pose a growing threat to public health, and anti-microbial peptides (AMPs) have great potential as efficient treatment alternatives. Houseflies have evolved over long periods in complex, dirty environments, developing a special immune system to overcome challenges in harmful environments. AMPs are key innate immune molecules. Herein, two differentially expressed AMPs, Phormicins A and B, were identified by screening transcriptomic changes in response to microbial stimulation. Structural mimic assays indicated that these AMPs exhibited functional divergence due to their C-terminal features. Expression analysis showed that they had different expression patterns. Phormicin B had higher constitutive expression than Phormicin A. However, Phormicin B was sharply downregulated, whereas Phor-micin A was highly upregulated, after microbial stimulation. The MIC, MBC and time-growth curves showed the antibacterial spectrum of these peptides. Crystal violet staining and SEM showed that Phormicin D inhibited MRSA biofilm formation. TEM suggested that Phormicin D disrupted the MRSA cell membrane. Furthermore, Phormicin D inhibited biofilm formation by downregulating the expression of biofilm-related genes, including altE and embp. Therefore, housefly Phormicins were functionally characterized as having differential expression patterns and antibacterial & antibiofilm activities. This study provides a new potential peptide for clinical MRSA therapy.

Automated summary

Antibiotic-resistant bacteria pose a threat to public health, and housefly AMPs have potential as treatment alternatives. This study identified differentially expressed AMPs in houseflies and characterized their expression patterns and antibacterial activities. The findings provide a new potential peptide for clinical MRSA therapy.