Publications

Fungus-growing termites engage in an obligate mutualistic relationship with Termitomyces fungi, which they maintain in monocultures on specialised fungus comb structures, without apparent problems with … infectious diseases. While other fungi have been reported in the symbiosis, detailed comb fungal community analyses have been lacking. Here we use culture-dependent and -independent methods to characterise fungus comb mycobiotas from three fungus-growing termite species (two genera). Internal Transcribed Spacer (ITS) gene analyses using 454 pyrosequencing and Illumina MiSeq showed that non-Termitomyces fungi were essentially absent in fungus combs, and that Termitomyces fungal crops are maintained in monocultures as heterokaryons with two or three abundant ITS variants in a single fungal strain. To explore whether the essential absence of other fungi within fungus combs is potentially due to the production of antifungal metabolites by Termitomyces or comb bacteria, we performed in vitro assays and found that both Termitomyces and chemical extracts of fungus comb material can inhibit potential fungal antagonists. Chemical analyses of fungus comb material point to a highly complex metabolome, including compounds with the potential to play roles in mediating these contaminant-free farming conditions in the termite symbiosis.

Three terpene synthases from the termite associated fungus Termitomyces were functionally characterized as (+)-intermedeol synthase, (-)-gamma-cadinene synthase and (+)-germacrene D-4-ol synthase, with … the germacrene D-4-ol synthase as the first reported enzyme that produces the (+)-enantiomer. The enzymatic mechanisms were thoroughly investigated by incubation with isotopically labeled precursors to follow the stereochemical courses of single reaction steps in catalysis. The role of putative active site residues was tested by site directed mutagenesis of a highly conserved tryptophan in all three enzymes and additional residues in (-)-gamma-cadinene synthase that were identified by homology model analysis.