Tolerance to chitosan by Trichoderma species is associated with low membrane fluidity

Area of Science:

• Mycology
• Biochemistry
• Agricultural Science

Background:

• Trichoderma spp. are vital biocontrol agents with broad applications.
• Chitosan, a biopolymer, is known to affect fungal growth.
• Understanding Trichoderma's response to chitosan is crucial for optimizing its use.

Purpose of the Study:

• To evaluate the impact of chitosan on the growth of four Trichoderma spp. isolates.
• To identify the most chitosan-tolerant isolate and characterize its properties.
• To investigate the relationship between fatty acid composition and chitosan tolerance.

Main Methods:

• Isolates identified using Internal Transcribed Spacer (ITS) of 18S ribosomal DNA (rDNA) sequencing.
• Radial growth inhibition assays with varying chitosan concentrations (0.5-2.0 mg/ml).
• Determination of Minimal Inhibitory Concentration (MIC) and Minimal Fungicidal Concentration (MFC).
• Analysis of free fatty acid composition, specifically linolenic acid (C18:3).

Main Results:

• Chitosan significantly reduced radial growth in all tested Trichoderma isolates in a dose-dependent manner.
• Trichoderma koningiopsis VSL185 exhibited the highest tolerance to chitosan, with a Minimal Inhibitory Concentration (MIC) >2000 μg/ml.
• Other Trichoderma isolates showed significantly lower MIC values, around 10 μg/ml.
• The chitosan-tolerant isolate, T. koningiopsis VSL185, had lower linolenic acid content compared to sensitive isolates.

Conclusions:

• Trichoderma koningiopsis VSL185 demonstrates remarkable tolerance to chitosan.
• Reduced membrane fluidity, associated with lower linolenic acid content, is a key factor in chitosan tolerance in Trichoderma spp.
• These findings provide insights into the mechanisms of chitosan resistance in fungi and can inform biocontrol strategies.