Are marine fungi our untapped biotech superstars?
Planktonic marine fungi live in the water column of our oceans, where they float freely with the tides and currents. Within marine ecosystems they are parasites of other organisms and ‘saprotrophs’ that are specialist digestors of complex organic matter. According to Michael Cunliffe from the United Kingdom’s Marine Biological Association, studies of marine fungi are comparatively rare, proving a barrier to a comprehensive understanding of their unique ecology. Indeed, it has been calculated that less than 1 % of all marine fungal species have been described, partly due to difficulties in conducting the necessary DNA sequencing and in growing lab cultures. “Perhaps most noteworthy, it was unknown if, and how, marine fungi display patterns of species diversity over time,” explains Cunliffe, coordinator of the MYCO-CARB project, which was funded by the European Research Council. The project succeeded not only in helping to fill these knowledge gaps but also in pointing to potentially fruitful avenues for future research into climate change and biotechnology resources.
Better understanding the marine fungal ecosystem
MYCO-CARB used two complementary approaches to study marine fungi: lab cultivation and direct analyses of marine samples without culturing. Seawater samples were collected by the team from locations ranging from the open Atlantic Ocean to the United Kingdom’s coastal sediments, and including marine seaweeds collected near the Marine Biological Association. Back at the lab, the samples were added to specialised growth media containing sea salts to cultivate them. Once grown, the fungi were isolated and after identifying the species, were added to the MYCO-CARB Marine Fungi Culture Collection. The team used a range of DNA and RNA tools to study the biology of specific isolates to better understand their ecology in the marine environment. “The diversity of marine fungal communities that we detected reveals much about their ecology and their fit within the wider coastal marine ecosystem,” says Cunliffe. “For the first time, we have shown that species change over monthly and seasonal timescales and can display similar patterns of species composition after these changes. This suggests that species are reoccurring over time, but we need more research to work out what the ecological drivers of this are.” An innovative way to study active saprotrophic fungi attached to marine particles was also developed by the project. “Individual organic particles, such as pieces of leaves and twigs, were isolated from seawater then assessed using microscopes allowing us to characterise the diversity of fungi hosted by them,” adds Cunliffe. RNA sequence data from the Tara Ocean Expedition was also used to analyse the activity of saprotrophic marine fungi across the global ocean, focusing on the carbohydrate-active enzymes (CAZymes) involved in degrading complex organic material. “Our work demonstrated that marine fungi are active saprotrophs, degrading complex carbon-rich organic matter in the open ocean. More work is now needed on their specific contributions to oceanic carbon cycling,” says Cunliffe.
Fungi offer a future biotech treasure trove
The establishment of the Marine Fungi Culture Collection at the Marine Biological Association in the United Kingdom, is a significant legacy of the project, offering the only resource of its kind. While MYCO-CARB used selected cultures to investigate their fundamental biology, the collection offers much more. “Marine fungi are a major untapped biotechnological resource and a potential source of valuable new biomolecules, such as antimicrobial compounds. Additionally, many of the fungi we isolated from seaweed could offer new ways to deal with marine biomass waste, such as that generated by the seaweed industry,” explains Cunliffe. For now, the team is focused on quantifying the role of marine fungi in carbon cycling compared with other marine life such as bacteria, while also exploring new opportunities to maximise the collection’s cultures.
Keywords
MYCO-CARB, marine fungi, ecosystem, saprotrophs, biotechnology, ecology, seaweed, carbon cycling
