HOW DOES ZN INFLUENCE THE METALS REMEDIATION OF A NEW MN-OXIDIZING FUNGUS (CURVULARIA LUNATA TC1)?

Manganese (Mn) oxides are important minerals in the natural environment because they can act as natural sponges to adsorb metals from water. In nature, the oxidation of aqueous Mn (II) to form the insoluble Mn (III/IV) oxide minerals is largely driven by microbial activities through enzymatic and metabolite-mediated pathways. These biogenic oxides exist as highly reactive phyllomanganates to scavenge multiple metals. For environmental remediation, fungal Mn oxides are of particular importance because diverse Mn-oxidizing fungi can survive in harsh environments and are prevalent in many metal-polluted sites. In these sites, multiple metals usually exist as co-contaminants, which may affect the formation of fungal Mn oxides and decrease their ability to sequester metal contaminants. Zinc (Zn) is a common metal co-contaminant in natural metal-impacted sites and can be harmful to animals and humans due to its toxicity when the concentration is high. Previous research has shown that the formation of Mn oxides by Mn(II) oxidizing bacteria can be inhibited by Zn via changing the structure of the oxidases. However, it remains unknown if Zn inhibits fungal Mn oxidization as a similar mechanism to bacteria.

We have isolated a new fungus (Curvularia lunata TC1) from the wastewater at Tar Creek superfund site located in northeast Oklahoma. This fungus was capable of oxidizing Mn(II). From the initial results, a high concentration of Zn inhibited the formation of Mn oxides. However, the growth of the fungus wasn’t inhibited. Interestingly, this phenomenon wasn’t found in other Mn-oxidizing fungi (Alternaria alternata, Plectosphaerella cucumerina, Pyrenochatta sp., Paraconiothyrium sporulosum, Stagonospora sp.). This result may be due to the inhibition of specific Mn oxide-related enzymes by Zn. We are inoculating our fungus in AY media with various amounts of Mn/Zn to determine the oxidation pathway of this fungus. The mRNA will be extracted for transcription analysis by Illumina Nextseq^® 550 to find the differentially expressed genes. The extracellular metabolite and intracellular Mn oxide-related enzymes will be separated using standard native PAGE and identified by LC/MS/MS. Results from this study aim to reveal the pathway of fungus TC1 and may provide new insight into the process of biogenic Mn oxidation.