Metabolic profiling of early cellulose-decomposing microfungi in Mediterranean natural environment

Cellulose is the most abundant organic compound in the biosphere. A considerable number of fungi were described as having the power to attack cellulose, and several studies on the in vitro dynamic of cellulose degradation by filamentous fungi have been published, but little is known about the fungal communities colonizing cellulose under natural conditions. The aim of this study was the metabolic profiling, and the evaluation of niche overlap of microfungi that act as early cellulose colonizer in a Mediterranean natural environment. Filter paper layers (10cm2) of pure cellulose (cotton linter) were overlapped to obtain a pad, which was stored in a terylene square net bag (15 cm2) with a mesh size of 1 mm2, and incubated for 45 days (from April 2007) under the leaf litter of a low mixed Mediterranean maquis, in the Natural Reserve of Castel Volturno, southern Italy (408570N; 138550E). Four different sites as field replicates were considered. Microfungi occurring on the cellulose layers were sampled, cultured, and identified by sequencing the ITS1-5.8S-ITS2 regions of the rDNA. Functional diversity of single fungal isolates was analysed using the carbon source phenotype microarray technique (BiologTM FF microplates). Some species prevailed, but interestingly not overlapped each other in the field sites. The comparison of functional diversity of cellulolytic isolates like Stachybotrys chartarum, Cladosporium tenuissimum, Alternaria alternata, Hypocrea lixii and Minimedusa polyspora showed an inter-site metabolic redundancy, but an intra-site diversity which indicated the importance of some taxa with a very high functional potential in early stages of cellulose decomposition.