Aspergillus does not have mushroom for your environmental negligence

The occurrence of oil spills has been steadily reducing since the 1970’s, but they still cause a huge amount of damage to the local ecosystem when they do happen. Chemical dispersants can be used but as well as being expensive, they just change the oil into a different phase rather than removing it. Multiple recent studies have documented the rapid proliferation of Fungi after an oil spill event (Bik et al 2012, Taylor & Cunliffe 2015) yet research into bioremediation has almost always been focused on Bacteria. Fungi would be suitable candidates for bioremediation agents as some have been shown to utilise some polycyclic aromatic hydrocarbons and they also produce surfactants which are important as they reduce surface tension and increase the uptake of crude oil. Bovio and colleagues looked into this possibility by isolating and identifying the fungal community of a recently contaminated site (Gela, Sicily 2013), and assessed the capability of the isolates to use crude oil as their sole carbon source.

Water and sediment samples were collected three days after the spill in June, and after being transported to the lab the water was filtered through sterile membranes. The membranes were transferred onto petri dishes containing antibiotics to remove bacteria, and incubated at 24^oC for a month to allow slow growing colonies to appear. Strains were isolated in pure culture for identification. The water sample contained 67 taxa from 29 different fungal genera, and 12 of these species have not been previously recorded in a marine environment, but I take this statement lightly as often fungi are only identified to genus level. The sediment sample contained 17 taxa from 12 genera. In both samples, almost all of the genera belonged to the division Ascomycota.

All of the fungi were grown on crude Arabian Light Oil to see if they could use it as their sole carbon source, and about a quarter of the water-derived and sediment-derived fungi (24% and 22% respectively) were significantly stimulated by the presence of the crude oil. Different strains of the same species reacted differently to the presence of oil, showing that there is large intraspecific variability. Four strains that had the highest amount of stimulation were selected and evaluated for their ability to degrade oil in a liquid culture. Aspergillus terreus MUT 271 exhibited the highest hydrocarbon removal potential, by removing 40% of oil compounds from the water, followed by Penicillium citreonigrum MUT 267 with 24%.

This study is very in-depth, but the authors took all of their water samples from one metre depth, which may have excluded any fungi which reside in the sea surface microlayer (SML). The SML may play an important part in oil degradation since it will be the first point of contact for the hydrophobic oil layer, therefore is important not to overlook. The use of fungi as potential bioremediators has been neglected so far, but this study provides a strong base for further research to investigate the viability of A. terreus MUT 271 and P. citreonigrum MUT 267 for this purpose. It would be interesting to see whether A. terreus MUT 271 and P. citreonigrum MUT 267 can be found at other sites as well as the Mediterranean, and whether they can remove oil as effectively in these different climates.

Reviewed Paper;

Bovio E., Gnavi G., Prigione V., Spina F., Denaro R., Yakimov M., Calogeno R., Crisafi F., Varese G.C. (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

Referenced Papers;

Bik H.M., Halanych K.M., Sharma J., Thomas W.K. (2012) Dramatic Shifts in Benthic Microbial Eukaryote Communities following the Deepwater Horizon Oil Spill. PLoS ONE 7(6): e38550. doi:10.1371/journal.pone.0038550

Taylor J.D. & Cunliffe M. (2015) Polychaete burrows harbour distinct microbial communities in oil-contaminated coastal sediments. Environmental Microbiology Reports. 7: 606-613.