Cd and Zn interactions and toxicity in ectomycorrhizal basidiomycetes in axenic culture
- Subject Areas
- Microbiology, Mycology, Ecotoxicology, Environmental Contamination and Remediation
- heavy metal toxicity, metal interaction, Ectomycorrhizal fungi, toxicity threshold
- © 2018 De Oliveira et al.
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2018. Cd and Zn interactions and toxicity in ectomycorrhizal basidiomycetes in axenic culture. PeerJ Preprints 6:e26549v1 https://doi.org/10.7287/peerj.preprints.26549v1
Background. Metal contamination in soils affects both above and belowground communities, including soil microorganisms. Ectomycorrhizal (ECM) fungi are an important component in belowground community and tolerant strains have great potential in enhancing plant-based remediation techniques. We assessed cadmium and zinc toxicity in five ECM species in liquid media (Hebeloma subsaponaceum; H. cylindrosporum; H. crustuliniforme; Scleroderma sp.; Austroboletus occidentalis) and investigated the potential of Zn to alleviate Cd toxicity. Due to highly divergent results reported in the literature, liquid and solid media were compared experimentally for the first time in terms of differential toxicity thresholds in Cd and Zn interactions. Methods. A wide range of Cd and Zn concentrations were applied to ectomycorrhizal fungi in axenic cultures (in mg L-1): 0; 1; 3; 9; 27; 81; 243 for the Cd treatments, and 0; 1; 30; 90; 270; 810; 2430 for Zn. Combined Zn and Cd treatments were also applied to H. subsaponaceum and Scleroderma sp. Dry weight was recorded after 30 days, and in case of solid medium treatments, radial growth was also measured. Results and Discussion. All species were adversely affected by high levels of Cd and Zn, and A. occidentalis was the most sensitive, with considerable biomass decrease at 1 mg L-1 Cd, while Scleroderma sp. and H. subsaponaceum were the most tolerant, which are species commonly found in highly contaminated sites. Cd was generally 10 times more toxic than Zn, which may explain why Zn had little impact in alleviating Cd effects. In some cases, Cd and Zn interactions led to a synergistic toxicity, depending on the concentrations applied and type of media used. Increased tolerance patterns were detected in fungi grown in solid medium and may be the cause of divergent toxicity thresholds found in the literature. Furthermore, solid medium allows measuring radial growth/mycelial density as endpoints which are informative and in this case appeared be related to the high tolerance indices found in H. subsaponaceum.
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Average tolerance index (%) based on the dry weight (DW) of four ectomycorrhizal fungi grown in liquid media containing different combinations of Cd and Zn doses (n = 4)
Three datasets containing the raw data of dry weight and radial growth of different ectomycorrhizal species under Cd and Zn stress
Sheet 1 - Dry weight of five ectomycorrhizal species exposed to a range of Cd and Zn concentrations (Data used for Fig. 1 and 2).
Sheet 2 - Dry weight of four ECM species exposed to a combination of different Cd and Zn concentrations (Data used for Fig. 3).
Sheet 3 - Dry weight and radial growth of Hebeloma subsaponaceum and Scleroderma sp exposed to a combination of Cd and Zn concentrations (Liquid media vs Solid media) (Data used for Table 2 and Fig. 4).