Isolation and Characterization of Mercury Resistant <i>Trichoderma</i> Strains from Soil with High Levels of Mercury and Its Effects on <i>Arabidopsis thaliana</i> Mercury Uptake

Abstract

Traditional mining activities are usually correlated with high levels of soil pollution, which is a major environmental concern. Extensive mining activities have taken place in the San Joaquin region in the State of Querétaro, México resulting in high levels of mercury soil pollution (up to 1532 ± 300 mg/kg). We isolated mercury-resistant fungal strains from the San Joaquin region soils and identified them through morphologic characteristics and ITS rDNA region sequence analysis. We determined that fungi isolated belong to the genus Trichoderma. All the isolates selected showed the ability to catalyze the volatilization of Hg. For air sampling, an active sampling device was constructed and using acid KMnO 4 as an absorbent, the concentration of mercury in solution was determined through the cold vapor atomic absorption method. The results show mercury volatilization from the fungal species assay, with a maximum of 213.04 ± 32.6 µg/m 3 while mycelium accumulation ranged from less than 17.5 ± 2.9 to 20.0 ± 3.4 µg/g. The fungal isolates were also evaluated for their ability to reduce mercury uptake in Arabidopsis thaHow to cite this paper: Hernández-Flores, J.L., Melo, J.G.B., Hernández, A.C., López, M.A.R., Gutiérrez, C.S., Gomez, S.R., Moreno, V.P., Medina, R.P.C., Soto, J.H.V., Hernández, S.P., Jones, G.H., Flores, S.C. and Campos-Guillen, J. (2018)

Heavy Metal-Resistant Filamentous Fungi as Potential Mercury Bioremediators

“…Thus, a uniform comparison is unattainable for such heterogeneous conditions. Under similar conditions to those herein, i.e., wet biomass in 100 mg/L Hg 2+ aqueous solution, reported Qs were 0.02 mg/g d.w. for an Hg-resistant Trichoderma virens isolate [ 80 ] and 336 mg/g d.w. for Lentinus edodes , with a 0.89 m 2 /g surface area [ 45 ]. Often, powdered fungal biomass was used as an Hg 2+ biosorbent because of its higher surface area, relative to live biomass, i.e., Q of 10 and 27 mg/g Hg 2+ in 100 mg/L Hg 2+ solution [ 115 , 117 ].…”

“…Hg 2+ removal and biosorption capacities of five distinct fungal species with superior Hg resistance, were established in aqueous solution supplemented with 100 mg/L Hg 2+ , similar to Zafar et al [ 32 ]. Water was selected, as our experiments in Luria Bertani and PDB media, that were used by other authors in similar conditions [ 39 , 80 ], resulted in important media-driven Hg loss. Seven-day-old PDA fungal cultures were used to prepare the spore suspensions (10 6 spores/mL).…”

Understanding the role of SilE in the production of metal nanoparticles by Morganella psychrotolerans using MicroScale Thermophoresis

“…Assuming that the heat-induced changes in diffusion detected by MST reflect direct binding of a single metal ion to the protein, SilE showed a good affinity to Ag + and Cu 2+ , with a dissociation constant, Kd, of 0.17 mM and 0.13 mM respectively (Figure 1A and 1B). The binding affinity was statistically significant with a Kd confidence of 6.0x10 5 , 4.0x10 5 and 6.0x10 5 for Ag + and 4.2x10 5 , 3.2x10 5 and 4.0x10 5 for Cu 2+ (3 replicates for each metal). This is consistent with the literature; it has been well established that SilE binds to both metals, and it was hypothesised to be in the µM range [21].…”

“…While metal ions such as calcium, copper, chromium, nickel and zinc are required for a variety of vital cellular processes [2,3] when in excess they become toxic to the cell, leading to cell death. To counter metal accumulation in the cell, bacteria have evolved intricate systems to maintain the correct internal concentration of metal ions [4,5].…”

“…Each mechanism is therefore specific to one or a small number of metals with similar characteristics. Such systems include the widely studied Mer pathway that reduces ionic Hg 2+ to Hg 0 in some Trichoderma strains [5], the Gram-negative based Cu tolerance system composed primarily of the copper sensor protein CueR and copper export pump CopA [6], and the Cus pathway in E. coli that is specialised in exporting Cu ions [5,7].…”