How can fungi help in bioremediation?

Oil spills in the marine environment can cause severe detrimental effects to the environment and to the organisms that live there – in 2002, after the Prestige oil spill (Galicia, North Spain), the most affected beaches lost up to 66.7% of their species richness just 8 months after the accident (de la Huz et al., 2005). There are many different techniques used in the clean-up of oil spills; including in-situ burning, the use of chemical dispersants and, more recently, the use of micro-organisms in bioremediation (Bovio et al., 2017).

The recent study by Bovio et al., aimed to look at the fungal community of an Italian marine site that had been contaminated by an oil spill. The authors wanted to understand what role fungi play in bioremediation, and to assess its capability of using crude oil as a sole Carbon source.

To do this, seawater and sediment samples were collected 3 days after the oil spill. All samples were transferred to mediums containing antibiotics and left for 1 month to allow fungal communities to colonise – each strain was then isolated in pure culture for taxonomic and genomic identification. All 142 isolated fungi were tested for their capabilities to grow on crude oil as the sole Carbon source and four strains were then tested for their capability to degrade oil in liquid cultures. The efficiency of petroleum degradation was then estimated.

Their results showed that 94% of recorded taxa belonged to Ascomycota, which aligns with similar literature (for example: Jones et al., 2015). In this study, they also identified 12 fungal species from seawater samples, and 14 from sediment samples that had not been previously recorded in a marine environment – presumably, these species are therefore only present in the area due to the oil contamination. ~20% of isolates from both sample groups were significantly stimulated by the presence of crude oil, ~45% were insensitive and ~30% were inhibited. What I found particularly interesting about these results was that strains belonging to the same species were seen to exhibit different behaviours (showing that there is huge intraspecific variability within these fungal communities). For example, S. racemosum had 9 strains that were inhibited by the crude oil presence, 1 strain that was insensitive and 1 strain that was inhibited.

The authors found that fungi use the crude oil as a source of nourishment, as fungal biomasses were significantly higher in the presence of crude oil than in its absence. All fungal isolates exhibited moderate removal capabilities of petroleum hydrocarbons and ¼ of these strains were stimulated by the presence of crude oil, displaying vigorous growth in its presence.

To take this study further, I think that it’s important to look at how fungal strains are able to degrade crude oil in nature as a comparison to what has been observed in the laboratory. There is obviously a huge potential for fungal communities in bioremediation, and in future they could come in useful for clean-up operations.

Studied paper

Bovio, E., Gnavi, G., Prigione, V., Spina, F., Denara, R., Yakimov, M., Calogero, R., Crisafi, F., Varese, G. (2017). The culturable mycobiota of a Mediterranean marine site after an oil spill: isolation, identification and potential application in bioremediation. Science of the Total Environment (576), 310-318.

References

De la Huz, R., Lastra, M., Junoy, J., Castellanos, C., Vieitez, J. (2005). Biological impacts of oil pollution and cleaning in the intertidal zone of exposed sandy beaches: Preliminary study of the “Prestige” oil spill. Estuarine, Coastal and Shelf science (65), 19-29.

Jones, E.B.G., Suetrong, S., Sakayaroj, J., Bahkali, A.H., Abdel-Wahab, M.A., Boekhour, T., Pang, K.L. (2015). Classification of marine Ascomycota, Basidiomycota, Blastocladiomycota and Chytridiomycota. Fungal Divers (73), 1-72.