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 KMnO4 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/m3 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 thaliana. These observations suggest the utility of Trichoderma for the mobilization of mercury in those contaminated soils.
Highlights
The San Joaquin region is a unique locality in Querétaro State, which has an extensive history of commercial-scale mercury extraction in México
Soil samples were serially diluted in potato dextrose broth (PDB; Difco; Detroit, MI, USA) and immediately thereafter, 0.1 ml was spread over potato dextrose agar medium (PDA; Difco; Detroit, MI, USA), amended with 50 mg∙L−1 of HgCl2
We selected three isolates for further study based on their ability to grow in the presence of higher concentrations of HgCl2 (100 and 200 mg∙L−1) and for their clear ability to catalyze the volatilization of Hg as accessed via the non-radioactive X-ray method [14]
Summary
The San Joaquin region is a unique locality in Querétaro State, which has an extensive history of commercial-scale mercury extraction in México. Diverse investigations have shown the detrimental effects of mercury in various organisms, the ability of several microbial species to detoxify Hg has been reported [3]. Both Gram negative and Gram positive bacteria are able to detoxify Hg(II) by converting it to the volatile and less toxic form, Hg0 [4] [5]. Mercury resistance mechanisms have been well studied in several bacterial species. It is mediated by the transcriptional activator, MerR; in the presence of Hg(II) the mer operon is expressed. Previous work from our laboratory showed that microorganisms associated with the rhizosphere of plants that grow in soils contaminated with high metal concentrations may possess the genetic machinery to produce resistance to mercury [2]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
