190 Mycologia, 94(2), 2002, pp. 190–199.  2002 by The Mycological Society of America, Lawrence, KS 66044-8897 A 13 C-NMR study of exudation and storage of carbohydrates and amino acids in the ectomycorrhizal edible mushroom Cantharellus cibarius J. Ignacio Rangel-Castro 1 Eric Danell Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences (SLU), Box 7026, SE-750 07 Uppsala, Sweden Philip E. Pfeffer Plant-Soil Biophysics, United States Department of Agriculture-Agricultural Research Service, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA Abstract: 13 C-NMR analyses of Cantharellus cibarius growth media were performed. We found exudation of trehalose and mannitol, which may explain the phenomenon of reproducing Pseudomonas bacteria observed inside fruit bodies. Exudation varied with strain and environment. NMR analyses of stored 13 C was also performed. Trehalose, mannitol, and argi- nine were revealed. The mannitol pathway seems to play an important role for trehalose production in this species. This is the first study of the fate of the photosynthetically derived carbon in the highly ap- preciated edible ectomycorrhizal mushroom Can- tharellus cibarius. Key Words: arginine, chanterelle, mannitol, me- tabolism, mycorrhiza, trehalose INTRODUCTION Studies of carbohydrate metabolism in several ecto- mycorrhizal (ECM) (Martin et al 1984, 1985, 1988, 1998, Hampp and Schaeffer 1995, Smith and Read 1997) and non ECM fungi (Hammond and Nichols 1976, Wannet et al 1998, 1999, 2000) have been per- formed in the past few years. Trehalose (alpha-D-Glu- copyranosyl-(1–1)alpha-Glucopyranoside) and man- nitol have been found as the major carbon com- pounds stored in mycelia of the studied ECM fungi (Martin et al 1985, 1988, 1998, Ramstedt et al 1989). Exudation of some other sugars and polyols were found by Yu-Ping et al (1999) on hyphal tips of the ectomycorrhizal fungus Suillus bovinus. Storage and exudation are two processes that might be affected by external conditions such as temperature and pH Accepted for publication September 4, 2001. 1 Corresponding author, Email: Ignacio.Rangel@mykopat.slu.se of the surrounding medium. For instance, trehalose production has been considered as a possible toler- ance response when fungi grow under stress condi- tions (Mellor 1992). The golden chanterelle, Cantharellus cibarius Fr., is an economically important edible ectomycorrhizal mushroom (Danell 1999, Watling 1997), phylogenet- ically distant from the euagarics such as Agaricus, Lac- caria or Boletus (Hibbett et al 1997). The genetic dif- ferences may imply also differences in physiology and ECM formation processes in comparison with other mycorrhizal basidiomycetes (Danell 1999). The com- prehension of the physiology of C. cibarius is an im- portant step towards optimized artificial cultivation. The problems in obtaining pure cultures of C. cibar- ius due to bacterial contamination (Straatsma et al 1985, Danell 1994a) explain why such studies are scarce. Previous attempts to find exudates that could explain the presence of large numbers of bacteria in fruit bodies have failed (Danell 1994a). Most of the physiological studies in C. cibarius have been focused on aspects of basic nutrient requirements in order to obtain axenic cultures (Straatsma and Van Griensven 1986, Danell 1994a, Danell 1999). From other studies on ECM fungi it is known that sucrose derived from photosynthesis of the host plant is degraded to glu- cose and fructose by the plant root invertase (Hampp et al 1995). However, the fate of glucose and fructose once assimilated by the C. cibarius mycelium is un- known, which is surprising considering the ecological and commercial importance of this mushroom (Da- nell 1999). We hypothesize that the chanterelle my- celia exude organic compounds, which may explain the growth of bacteria in fruit bodies. The aims of this investigation were (1) to identify the carbon compounds exuded by C. cibarius myce- lia, (2) to investigate the fate of glucose, and (3) to determine variation in exudation and storage due to strain, temperature and pH. 13 C-NMR is a powerful technique that has allowed improved understanding of the carbon metabolic routes of some ECM fungi. It provides the opportu- nity to follow the distribution of intermediates and final products after fungal assimilation in axenic cul- tures (Martin 1991). This technique was therefore chosen for this study.