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Evaluation of Phenolic Compound Toxicity Using a Bioluminescent Assay with the Fungus Gerronema viridilucens
Fernanda F Ventura1,2, Luiz F Mendes1,3, Anderson G Oliveira4
1Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
Abstract:
Basidiomycetes (phylum Basidiomycota) are filamentous fungi characterized by the exogenous formation of spores on a club-shaped cell called a basidium that are often formed on complex fruiting bodies (mushrooms). Many basidiomycetes serve an important role in recycling lignocellulosic material to higher trophic levels, and some show symbiotic relationships with plants. All known bioluminescent fungi are mushroom-forming basidiomycetes in the order Agaricales. Hence, the disruption of the basidiomycete community can entirely compromise the carbon cycle in nature from fungi to higher trophic levels. The fungus Gerronema viridilucens was used in the present study to investigate the toxicity of a phenolic compound series based on the inhibition of its bioluminescence. The median effect concentration (EC50) obtained from curves of bioluminescence inhibition versus log [phenolic compound] showed that 2,4,6-trichlorophenol was the most toxic compound in the series. The log EC50 values of all phenolic compounds were then used for the prediction of their toxicity. The univariate correlation of log EC50 values obtained from 6 different phenolic compounds was stronger with the dissociation constant (pKa ) than with 1-octanol/water partition coefficient (KOW ). Nevertheless, the toxicity can be better predicted by using both parameters, suggesting that the phenol-driven uncoupling of fungus mitochondrial adenosine triphosphate synthesis is the origin of phenolic compound toxicity to the test fungus. Environ Toxicol Chem 2020;39:1558-1565. © 2020 SETAC.
Insights
This study investigated phenolic compound toxicity in the bioluminescent fungus Gerronema viridilucens. The dissociation constant (pKa) better predicted toxicity than the octanol-water partition coefficient (KOW), suggesting mitochondrial uncoupling as the toxic mechanism.
Area of Science:
- Environmental Toxicology
- Mycology
- Biochemistry
Background:
- Basidiomycetes, including mushroom-forming fungi, are crucial for the carbon cycle and plant symbiosis.
- Bioluminescent fungi, exclusively in the order Agaricales, are sensitive indicators of environmental disruption.
- Phenolic compounds can disrupt ecological processes, necessitating toxicity assessments.
Purpose of the Study:
- To evaluate the toxicity of a series of phenolic compounds using the bioluminescent fungus Gerronema viridilucens.
- To correlate phenolic compound toxicity with physicochemical properties like dissociation constant (pKa) and octanol-water partition coefficient (KOW).
- To elucidate the mechanism of phenolic compound toxicity in fungi.
Main Methods:
- Assessed toxicity by measuring the inhibition of bioluminescence in Gerronema viridilucens exposed to various phenolic compounds.
- Determined the median effect concentration (EC50) for each compound.
- Performed univariate correlation analysis between log EC50 values and physicochemical parameters (pKa, KOW).
Main Results:
- 2,4,6-trichlorophenol exhibited the highest toxicity among the tested phenolic compounds.
- The dissociation constant (pKa) showed a stronger correlation with toxicity (log EC50) than the octanol-water partition coefficient (KOW).
- A combined model using both pKa and KOW provided a better prediction of phenolic compound toxicity.
Conclusions:
- Phenolic compound toxicity in Gerronema viridilucens is strongly linked to their pKa.
- The mechanism of toxicity likely involves the uncoupling of mitochondrial adenosine triphosphate (ATP) synthesis by phenolic compounds.
- This study provides a basis for predicting the environmental risk of phenolic pollutants to fungal communities.
