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Updated: Nov 16, 2025
Production and Visualization of Bacterial Spheroplasts and Protoplasts to Characterize Antimicrobial Peptide Localization
Published on: August 11, 2018
Ultrastructural changes in methicillin-resistant Staphylococcus aureus (MRSA) induced by a novel cyclic peptide ASP-1
Rehan Deshmukh1, Ajay Ghosh Chalasani1, Debprasad Chattopadhyay2
1Birla Institute of Technology and Science, Pilani, Department of Biological Sciences, Goa Campus, NH17B Bypass, Goa 403726, India.
Abstract:
Increasing antimicrobial resistance among Staphylococcus aureus necessitates a new antimicrobial with a different site of action. We have isolated a novel cyclic peptide-1 (ASP-1) from Bacillussubtilis with potent activity against methicillin-resistant S. aureus (MRSA) at a minimum inhibitory concentration (MIC) of 8-64μg/ml. Scanning electron micrographs demonstrated drastic changes in the cellular architecture of ASP-1 treated cells of S. aureus ATCC 29213 and an MRSA clinical isolate at MICs, with damages to the cell wall, membrane lysis and probable leakage of cytoplasmic contents at minimum bactericidal concentrations. The ultrastructure alterations induced by ASP-1 have also been compared with those of oxacillin-treated MRSA cells at its MIC using scanning electron microscopy.
Insights
A novel cyclic peptide, ASP-1, from Bacillus subtilis shows potent activity against methicillin-resistant Staphylococcus aureus (MRSA). ASP-1 causes significant cellular damage, offering a potential new antimicrobial strategy against resistant bacterial infections.
Area of Science:
- Microbiology
- Biochemistry
- Drug Discovery
Background:
- Antimicrobial resistance in Staphylococcus aureus, particularly MRSA, is a growing global health concern.
- There is an urgent need for novel antimicrobials with distinct mechanisms of action to combat resistant strains.
Purpose of the Study:
- To isolate and characterize a novel antimicrobial agent effective against MRSA.
- To investigate the mechanism of action of the isolated compound at the ultrastructural level.
Main Methods:
- Isolation of a cyclic peptide (ASP-1) from Bacillus subtilis.
- Determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against MRSA.
- Scanning electron microscopy (SEM) to visualize cellular ultrastructure changes induced by ASP-1.
Main Results:
- ASP-1 demonstrated potent activity against MRSA with MICs ranging from 8-64 μg/ml.
- SEM revealed significant alterations in bacterial cell architecture, including cell wall damage and membrane lysis.
- Ultrastructural changes induced by ASP-1 were observed at MICs and MBCs, indicating a disruptive effect on bacterial integrity.
Conclusions:
- ASP-1 is a promising novel cyclic peptide with potent bactericidal activity against MRSA.
- The observed ultrastructural damage suggests a unique mechanism of action, potentially targeting the bacterial cell envelope.
- ASP-1 represents a potential new therapeutic candidate for treating infections caused by drug-resistant Staphylococcus aureus.
