Conservation policies of governments, nature conservation and civil societies focus on charismatic animals like tigers and whales but not on microbes, especially the fungi.
The word fungus draws a bad press as some of them are pathogens of plant, animal and human, and as spoilers of food. But fungi, apart from edible mushrooms and yeasts used for wine and bread making, play a unique role in the biosphere by decomposing dead plants and animals thus functioning as major recyclers of nutrients. This is because fungi produce enzymes capable of breaking down recalcitrant biomass. Hence, there would be no life on this planet without fungi.
Fungi first appeared about a billion years ago; that they have not become extinct over a long period and their ubiquitous presence in almost all ecosystems endorse their evolutionary success and flexible adaptation strategies.
Owing to their extraordinary genes, fungi produce numerous unique metabolites and enzymes which can breakdown recalcitrant biomass. Some of these include the statins used for reducing cholesterol levels in the blood, antibiotics and immunosuppressant drugs.
Fungi colonise harsh and inhabitable niches such as radioactive rich places, rumen of herbivores, deep sea, hot springs, polluted environments and habitats high in temperature and salinity.
Of the 2-11 million estimated species of fungi, only a small fraction of 150,000 species have been discovered, despite such anthropocentrically positive attributes, according to a 2022 paper. This sidelining of fungi is endorsed by the fact that the Global Fungal Red List Initiative recorded only 625 fungal species in the global red list as recently as in December 2022.
Sponges collected from under the sea
Just like other living organisms, fungi are also threatened by habitat loss, decline of extinction of symbiotic hosts, over exploitation, and climate change. Realising this, the International Union for Conservation of Nature Species Survival Commission Fungal Conservation Committee in 2021 has called for ‘the due recognition of fungi as major components of biodiversity in legislation and policy’.
It is mandatory that fungal diversity is addressed more seriously to identify novel species hosting unique genes before they go extinct. One possibility to increase the chances of finding fungi with novel traits is to hunt for them in less-studied and harsh habitats.
Harsh niches include polluted ones, high in salts, high or low in temperature that could be colonised only by microbes adapted to such places. Hence, such environments harbour unique microbes whose interactions would result in their production of molecules not present in normal habitats.
Another less explored habitat is the internal tissues of plants. Just like the human and animal body, plants also harbour non-disease causing bacterial and fungal symbionts. Called the endophytes ('endo' means inside and 'phyte' means plant), the fungal symbionts are a constant and universal facet of the endobiome of plants.
In our study for the past 40 years, we have isolated more than 2,000 endophytic fungi from trees of dry deciduous forest, dry thorn forest and montane evergreen forest of the Western Ghats, mangroves of Andaman Islands, West Bengal, Andhra Pradesh, Tamil Nadu, Kerala, Karnataka, Goa and Gujarat, endemic plants and lichens of Arunachal Pradesh and seaweeds of Tamil Nadu and Andaman Islands.
Our research collaboration with various institute in India and abroad have shown that some these fungi have unique traits. They produce molecules which can inhibit drug resistant malarial parasite and human pathogenic yeast which are responsible for death of immunocompromised patients.
Some of our fungi produce water soluble melanin pigment which are known have antimicrobial, UV screening, antioxidative, and anti-inflammatory properties and could find use in space travel as radiation shield. This important since only bacteria have been studied to any extent for production water soluble melanin.
A few isolates of ours produce enzymes which could reduce the cost and increase the efficiency of bioethanol production from plant wastes and enzymes for converting chitin into smaller molecules of definite lengths which find use in biomedical applications including wound healing, drug, delivery, gene delivery, tissue engineering, drugs. We have also recorded that a few of our strains produce alkali and heat tolerant fat digesting enzymes. Some of them could be used for biological control of pests and weed.
In our current Science and Engineering Research Board (SERB), we are investigating the diversity and technological uses of fungi which live inside the tissues of marine sponges- another least studied habitats of fungi. In this research on marine sponges of Lakshadweep Archipelago, we have isolated 400 fungi from 15 sponge species. We are in the process of estimating their community structure, diversity, and some technological properties. When completed, it would be the largest sampling effort for fungi living inside marine sponges.
We have observed that some of these fungi produce chemicals which inhibit human pathogenic yeast like Candida albicans and Candida tropicalis as well as other fungi and bacteria. Candida tropicalis is a widely occurring human pathogenic yeast. This yeast has recently become resistant to the azole types of antibiotics which are used to control it.
This and the general increase in patients receiving chemotherapy for cancer and undergoing organ transplantation which reduce the immunity of the patients, has increased the infection caused by this yeast resulting in increased fatality. The WHO in 2022 has classified Candida tropicalis as a ‘high priority’ pathogen.
Though our results are basic and require several upstream processes to enable actual use, they approve the hypothesis that less studied habitats should be focused more rigorously for obtaining fungi of technological importance. Such focused bioprospecting for fungi, especially in tropical countries which support many different ecosystems and have a high plant and animal diversity, are bound to reveal novel fungi which could fined use in managing some of the major global issues such as antibiotic resistance among disease causing microbes and fossil fuel crises.
With this in mind, our lab has deposited more that 120 fungi exhibiting novel traits to National Culture Collection facilities in India. More assiduous study on fungi is bound to increase the genetic resource and the bioeconomy of the country.
MB Govinda Rajulu and TS Suryanarayanan are with the Vivekananda Institute of Tropical Mycology (VINSTROM) Ramakrishna Mission Vidyapith, Chennai.
Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth.