Role of the mutualistic fungus in lignin degradation in the fungus-growing termite Macrotermes gilvus (Isoptera; Macrotermitinae) F. Hyodo a, *, T. Inoue a, 1 , J.-I. Azuma b , I. Tayasu b , T. Abe a a Center for Ecological Research, Kyoto University, Kamitanakami Hirano-cho, Otsu, Shiga, 520-2113, Japan b Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan Accepted 3 October 1999 Abstract In order to investigate the role of the mutualistic fungus, Termitomyces sp., in the fungus-growing termite, Macrotermes gilvus, we applied CP/MAS 13 C NMR and selected proximate analyses to fungus comb of dierent ages and degrees of maturation. We found evidence that lignin degradation took place progressively in the fungus comb. In vitro digestibility of cellulose in old fungus comb, on which the termites feed, was approximately 3-fold higher than that in the fresh part. These results con®rm the `lignin degradation hypothesis' that the role of the mutualistic fungi is to degrade lignin and enhance the digestibility of cellulose for the termites, suggesting the ability of the termite±fungus association to make extremely ecient use of plant material. 7 2000 Elsevier Science Ltd. All rights reserved. Keywords: Fungus-growing termite; Lignin degradation; Cellulose digestibility; Macrotermes gilvus; Termitomyces sp. 1. Introduction Fungus-growing termites (Isoptera; Termitidae; Macrotermitinae) are abundant in the African and Asian tropics (Wood and Sands, 1978; Abe and Mat- sumoto, 1979). They play a signi®cant role in the de- composition of plant litter, for example consuming more than 90% of dry wood in some arid tropical areas (Buxton, 1981) and directly mineralizing up to 20% of the net primary production in wetter savannas (Wood and Sands, 1978). They have evolved an unique mutualism with basidiomycete fungi of the genus, Ter- mitomyces. The symbiotic fungi grow on a special cul- ture within the nest maintained by the termites and called `fungus comb'. The fungus comb is made from partly digested foraged plant litter which passes rapidly through the termite's gut. The resulting faecal pellets are pressed together to make a comb-like matrix. As the comb matures, mycelium develops and produces conidial nodules, which together with older, senescent comb are consumed by workers (Sieber and Leuthold, 1981). Because of the unique symbiotic relationship, many studies have been conducted on the termite±fungus as- sociation (reviews by Sands, 1969; Wood and Thomas, 1989; Darlington, 1994). Several roles have been suggested for the fungal symbiont, for example, the provision of heat and moisture (LuÈsher, 1951), the provision of a concentrated nitrogen source (as coni- dia, Matsumoto, 1976) and the enrichment of nitrogen in foraged foodstus by virtue of the fungal metab- olism (Collins, 1983). Soil Biology & Biochemistry 32 (2000) 653±658 0038-0717/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S0038-0717(99)00192-3 www.elsevier.com/locate/soilbio * Corresponding author. Tel.: +81-77-549-8200; fax: +81-77-549- 8201. E-mail address: fuji@ecology.kyoto-u.ac.jp (F. Hyodo). 1 Present address: Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-01, Japan.