A Staphylococcus capitis strain with unusual bacteriocin production.

Area of Science:

• Microbiology
• Bacteriology
• Genomics

Background:

• Staphylococcus capitis is a commensal skin bacterium, generally considered less pathogenic than Staphylococcus aureus.
• Antibiotic-resistant strains like methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-intermediate Staphylococcus aureus (VISA) pose significant public health challenges.
• Bacteriocin resistance in VISA strains is often linked to cell wall and membrane alterations.

Purpose of the Study:

• To investigate the antimicrobial properties of Staphylococcus capitis subsp. urealyticus BN2.
• To identify the compounds responsible for the antibacterial activity against resistant Staphylococcus aureus strains.
• To characterize the genetic basis of the antimicrobial substance production.

Main Methods:

• Isolation and cultivation of Staphylococcus capitis subsp. urealyticus BN2 from a feline source.
• Genomic sequencing to identify gene clusters for antimicrobial substance biosynthesis.
• Analysis of cell extracts and whole cells using mass spectrometry.
• Genetic manipulation (deletion of NRPS modules) to assess the role of specific compounds.
• In vitro competition assays against MRSA and VISA strains.

Main Results:

• Staphylococcus capitis subsp. urealyticus BN2 exhibited potent antibacterial activity against Gram-positive bacteria, including MRSA and VISA.
• Genomic analysis revealed gene clusters for gallidermin lantibiotic and a novel non-ribosomal peptide synthetase (NRPS).
• A novel bacteriocin, composed of decorated non-ribosomal peptides, was identified as a key anti-VISA agent.
• Phenol-soluble modulins (PSMs) were also detected and likely contribute to competitive exclusion.
• The strain successfully outcompeted MRSA and VISA in vitro.

Conclusions:

• Staphylococcus capitis subsp. urealyticus BN2 produces a combination of antimicrobial compounds, including a novel bacteriocin and PSMs.
• These compounds confer a competitive advantage against clinically relevant antibiotic-resistant Staphylococcus aureus strains.
• The findings suggest potential for developing new therapeutic strategies based on these antimicrobial substances.