Inhibitory Effect of Staphylococcus Epidermidis Fermentation Broth on Staphylococcus Aureus.

Area of Science:

• Microbiology
• Biochemistry
• Metabolomics

Background:

• Staphylococcus epidermidis (S. epidermidis) can produce antimicrobial compounds.
• Understanding the specific conditions and compounds responsible for inhibiting Staphylococcus aureus (S. aureus) is crucial for developing novel antimicrobial strategies.

Purpose of the Study:

• To optimize S. epidermidis fermentation conditions to produce an inhibitory effect on S. aureus.
• To identify the key metabolites and compounds responsible for the observed antimicrobial activity.

Main Methods:

• Cultivation of S. epidermidis in nutrient broth supplemented with glycerol (Gly-SFB) or glucose (Glu-SFB).
• Gas Chromatography-Mass Spectrometry (GC-MS) and High-Performance Liquid Chromatography (HPLC) for fatty acid analysis.
• Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS) with untargeted metabolomics to identify differentially abundant metabolites.
• Scanning Electron Microscopy (SEM) and Propidium Iodide (PI) staining to assess bacterial cell membrane integrity.
• Measurement of extracellular ATP levels.

Main Results:

• Gly-SFB and Glu-SFB significantly inhibited S. aureus growth, unlike S. epidermidis fermentation broth without supplements (SFB).
• Fatty acids, carboxylic acids, and derivatives, including peptides with lysine, arginine, and hydrophobic amino acid residues, were identified as key inhibitory compounds.
• Treatment with Gly-SFB or Glu-SFB compromised the S. aureus cell membrane, evidenced by increased extracellular ATP levels.
• Carbon source dependency altered S. epidermidis metabolism, leading to S. aureus growth suppression.

Conclusions:

• Optimized fermentation of S. epidermidis, particularly with glycerol or glucose, yields potent inhibitors of S. aureus.
• The antimicrobial activity is attributed to fatty acids and specific peptide metabolites disrupting the S. aureus cell membrane.
• Synergistic interactions between these compounds are crucial for the overall inhibitory effect.