Fungus-growing termites efficiently decompose plant litter through their symbiotic relationship with basidiomycete fungi of the genus Termitomyces. Here, we investigated phenol-oxidizing enzymes in symbiotic fungi and fungus combs (a substrate used to cultivate symbiotic fungi) from termites belonging to the genera Macrotermes, Odontotermes, and Microtermes in Thailand, because these enzymes are potentially involved in the degradation of phenolic compounds during fungus comb aging. Laccase activity was detected in all the fungus combs examined as well as in the culture supernatants of isolated symbiotic fungi. Conversely, no peroxidase activity was detected in any of the fungus combs or the symbiotic fungal cultures. The laccase cDNA fragments were amplified directly from RNA extracted from fungus combs of five termite species and a fungal isolate using degenerate primers targeting conserved copper binding domains of basidiomycete laccases, resulting in a total of 13 putative laccase cDNA sequences being identified. The full-length sequences of the laccase cDNA and the corresponding gene, lcc1-2, were identified from the fungus comb of Macrotermes gilvus and a Termitomyces strain isolated from the same fungus comb, respectively. Partial purification of laccase from the fungus comb showed that the lcc1-2 gene product was a dominant laccase in the fungus comb. These findings indicate that the symbiotic fungus secretes laccase to the fungus comb. In addition to laccase, we report novel genes that showed a significant similarity with fungal laccases, but the gene product lacked laccase activity. Interestingly, these genes were highly expressed in symbiotic fungi of all the termite hosts examined.

Fungus-growing termites cultivate fungi of the genus Termitomyces in gardens inside their nests. Despite various reports of the presence of Termitomyces in these gardens, the entire fungal community structure of the gardens has not yet been described. To clarify whether the fungal crops in the gardens are monocultures of Termitomyces, we examined 18 fungus gardens derived from 5 species of fungus-growing termites covering 3 genera. Phylogenetic analysis of DNA sequences revealed that non-Termitomyces fungi might have inhabited the gardens. However, terminal restriction fragment length polymorphism (T-RFLP) analysis clearly demonstrated that non-Termitomyces fungi made up only a minor population within the gardens. This suggests that the fungus gardens were maintained as almost complete monocultures of Termitomyces.

Termitomyces-related symbiotic basidiomycetes in the nests of fungus-growing termites (Macrotermitinae) of several genera in Thailand were cultivated and analyzed phylogenetically based on the DNA sequence of nuclear ribosomal RNA genes. The relationships of the symbiotic fungi with host termites and their locality were apparently complex, supporting intricate mechanisms for the termites to acquire the symbionts.