We have confirmed that termite fungus combs are vastly dominated by Termitomyces, and showed that this is not driven by obligate gut passage of substrates. This points to key behavioural and chemical defences of termite or the food fungus, Termitomyces. This is in line with our discovery that termites avoid substrates with virulent pathogens, and that termites rapidly use soil to cover exposed fungal gardens (WPIII). Cultivation efforts have allowed us to establish a series of putative pathogens to be used to test defences (WPII-III) and for future experimental evolution work. Gut metabolome analyses from South African species, including network analyses and caste-specific compound identification (WPI) documented a chemical environment that is unlikely to be antimicrobial, aligning with the absence of inhibition during gut passage. This further lend support to our hypothesis that Termitomyces and the fungus comb environment is critical in defence, for which we have documented both antimicrobial properties of combs, a headspace environment with high carbon dioxide that suppresses growth and/or sporulation of putative antagonistic fungi of the symbiosis as well as a rich set of volatiles of fungal origin (WPI, III). Volatiles are likely to play a key prophylactic role in the symbiosis as the environment within which Termitomyces is maintained is sealed from the surroundings. Gut metagenomics has proven challenging for biosynthetic gene cluster (BGC) characterisation, because of fragmented metagenomes and challenges associated with linking gene clusters to metabolites present in these complex environments. We have therefore taken a novel approaches to metabarcode BGC domains of non-ribosomal peptides in guts and fungus combs, which has proven succesful and revealed extraordinary diversity, pointing to strong selection for the evolution of chemical novelties and the absence of a conserved set of bacteria-derived compounds. This supports that the prospects for novel compound discovery remains high, despite past efforts to identify chemical compounds of actinobacterial origins in the symbiosis.
A major goal of this action has been to improve protocols for establishing fungus-growing termites in the laboratory in the Ivory Coast where we perform field work and subsequently at the University of Copenhagen (WPIII). As expected, this has proven challenging, with our initial efforts nevertheless providing promising insights into the conditions that favour successful setups. Specifically, we attempted to establish >400 queen and king pairs of Ancistrotermes cavithorax in the laboratory in Copenhagen, but establishment of fungal gardens proved to be a critical point during the colony life cycle, with consequently very low success rates. We continued to work with local field assistants and collaborators in Ivory coast and now have a few colonies in the lab in Copenhagen.
Major recent achievements include a comprehensive review published in Natural Product Reports (Schmidt et al. 2022), which is associated with a manually curated online database (
WPI(opens in new window), publication of termite gut metabolomes (Vidkjær et al. 2022) and microbial impacts on termite biology (Murphy et al. 2022) (WPI,III). We have finalised comparative genomics analyses of 39 Termitomyces genomes (20 species) and established their evolutionary histories (Schmidt et al. in revision). These analyses – along with volatile analyses (Kreuzenbeck et al., 2022; Vidkjær et al. in preparation; Yang et al. in preparation) – support that Termitomyces plays a major role in defence (WPI,II). The use of volatile terpenes in defence is possible because the termites ensure an enclosed, homeostatic environment that ensure constant temperature and humidity. This allows for CO2 build-up well beyond what most organisms can tolerate (5% or higher), and we have therefore also tested whether extremely high CO2 help protect from fungal infections, which appears to be the case (Schmidt et al. 2023); thus indicating that the environment acts as an additional layer of defence of the farming symbiosis (WPIII).
