Antibiotic activity of the pyrenocines

Area of Science:

• Agricultural Science
• Microbiology
• Mycology

Background:

• Pyrenochaeta terrestris produces pyrenocine A, a phytotoxin with known antibiotic properties.
• Understanding the spectrum of activity and mode of action of pyrenocine A is crucial for potential applications.

Purpose of the Study:

• To investigate the antibiotic activity of pyrenocine A against various plant pathogens, fungi, and bacteria.
• To determine the effective doses (ED50s) for different organisms and assess its biostatic versus biocidal potential.

Main Methods:

• Bioassays were conducted to determine the effective doses (ED50s) for inhibiting onion seedling elongation.
• Fungal spore germination and mycelial growth inhibition assays were performed for Fusarium oxysporum, Mucor hiemalis, and Rhizopus stolonifer.
• Bacterial growth inhibition assays were performed against Gram-positive and Gram-negative bacteria.

Main Results:

• Pyrenocine A effectively inhibited onion seedling elongation (ED50 = 4 µg/mL) and fungal spore germination (ED50s ranging from 14-25 µg/mL).
• It also inhibited mycelial growth of P. terrestris (ED50 = 77 µg/mL) and F. oxysporum (ED50 = 54 µg/mL).
• Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) were more susceptible (ED50s = 30-45 µg/mL) than Gram-negative bacteria (Escherichia coli, ED50 = 200 µg/mL), with Pseudomonas aeruginosa showing resistance.

Conclusions:

• Pyrenocine A demonstrates significant antibiotic activity against a range of plant pathogens and microorganisms.
• The compound acts primarily as a biostatic agent, allowing for recovery upon removal, suggesting potential for controlled applications.
• Pyrenocines B and C exhibited minimal antibiotic activity in the performed bioassays.