Solid-state NMR spectroscopy reveals unique properties of Trichoderma harzianum cell wall components

Abstract

Trichoderma harzianum is a saprophyte and a mycoparasite and is also capable of forming symbiotic connections with plants. This fungus interacts with the (a)biotic environment through its cell wall and as a mycoparasite secretes enzymes that degrade the cell wall polymers of its target fungi. The organization of the T. harzianum cell wall is not well known. We used solid-state NMR and Fourier transform infrared spectroscopy to probe the molecular composition and architecture of the T. harzianum cell wall at the atomic level. Our results revealed that the inner core of the T. harzianum rigid cell wall phase is largely composed of chitin, which is complemented with a more mobile cell wall layer that contains β-(1,3)-glucan. The outer dynamic phase of the cell wall is mainly composed of α- and β-glucans, arabinan, mannan and proteins. The relative abundance of both rigid and dynamic cell wall components changed when T. harzianum was grown on isolated fungal cell wall material instead of glucose. Our results suggest that T. harzianum forms a cell wall that is chemically distinct from other fungal species to prevent harmful self-digestion by its secreted lytic enzymes that do degrade the cell wall of target fungi.