| Summary: | Nickel contamination is a serious environmental issue that requires immediate action. In this study, 23 strains of <i>Trichoderma</i> were isolated from terrestrial and marine environments and identified using a polyphasic approach of morphological characterization and ITS gene sequence analysis. The <i>Trichoderma</i> strains were tested for their tolerance and biosorption of nickel. Our results showed the growth of all <i>Trichoderma</i> strains on Trichoderma Selective Medium (TSM) with 50–1200-ppm nickel, indicating their tolerance of this heavy metal even at a relatively high concentration. Six <i>Trichoderma</i> strains (three isolated from terrestrial substrates and three from marine substates) had the highest radial growth on TSM with 50-ppm Ni. Among these fungal isolates, <i>Trichoderma asperellum</i> (S03) isolated from soil exhibited the best growth after 2 days of incubation. For the biosorption of nickel, the accumulation or uptake efficiency by the six selected <i>Trichoderma</i> was determined in Potato Dextrose Broth (PDB) supplemented with 50-ppm Ni using a Flame Atomic Absorption Spectrophotometer (AAS). The percent uptake efficiency of the three strains of <i>T. asperellum</i> (S03, S08, and LL14) was computed to be up to 66%, while <i>Trichoderma virens</i> (SG18 and SF22) and <i>Trichoderma inhamatum</i> (MW25) achieved up to 68% uptake efficiency. Observation of the <i>Trichoderma</i> strains with Scanning Electron Microscopy (SEM) before and after the absorption of nickel showed very minimal damage on the hyphal and conidial surface morphology, but changes in the colonial characteristics were observed. Our study highlighted the potential of terrestrial and marine strains of <i>Trichoderma</i> for the bioremediation of nickel pollution.
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