Table 2.

Mechanisms of tolerance to metals in Trichoderma.

Strain	Metal resistance	Mechanism	References
T. asperellum	Fe, Cu, Mn, and Zn	Production of iron chelators (siderophores)	de Santiago et al., 2011
	Cu	Increase in catalase and peroxidase activity	Juniors et al., 2020
T. atroviride	Cu, Cd, and Zn	Biosorption by physical binding to negatively charged groups on the cell wall	Errasquin and Vazquez, 2003
	Zn, Ba, and Fe	Biosorption by functional groups with metal complexion capacity in the cell wall	Kacprzak and Malina, 2005
	Cu	Adsorption into the cell wall and absorption	Yazdani et al., 2010a
T. brevicompactum	Cu, Cr, Cd, Zn, and Pb	Biosorption and bioaccumulation by physical binding to negatively charged groups on the cell wall	Zhang et al., 2020
T. harzianum	Zn, Pb, Cd, and Hg	Increase of OASTL activity and transformation of cysteine into chelators like metallothioneins, phytochelatins, etc.	Raspanti et al., 2009
	Hg	Synthesis of hydrophobin by up-regulation of the gene encoding hydrophobin	Puglisi et al., 2012
T. viride	Zn(II), Pb(II), and Cd(II)	Ion exchange and adsorption	Ali and Hashem, 2007
Trichoderma sp.	Ni, Cd, and Cr	Adsorption and absorption by functional groups	Chew et al., 2012
	Pb, Zn, Cd, and Cu	Intracellular accumulation and melanin development	Ayad et al., 2018
T. asperelloides, T. hamatum, and T. harzianum	Cd, Cu, Hg, and Zn	Production of chelating substances and proteins; metal transport pathways inside the cells	Maldaner et al., 2020
T. asperellum and T. harzianum	Cd, Pb, and Ni	Biosorption by constituents and functional groups on the cell wall	Hoseinzadeh et al., 2017

The strain of Trichoderma, the metal(s) to which it is tolerant, and the proposed mechanisms of tolerance are shown.