Polysaccharides and phenolic compounds as substrate for yeasts isolated from rotten wood and description of Cryptococcus fagi sp.nov.

Abstract

Pieces of rotten wood collected in the forest were screened for the presence of yeasts. In spring time 3 tree species were sampled, followed by 9 species in summer. Yeast strains were identified by traditional methods. Identifications were confirmed by sequencing of ribosomal DNA in case of doubt. In total 14 yeast species of ascomycetous affiliation and 6 anamorphic basidiomycetous yeasts were isolated and identified. Most species were represented by only one strain, but Candida bertae by two and Trichosporon porosum by six strains, all from different wood samples. Three strains represented novel species, one of which is described as Cryptococcus fagi Middelhoven et Scorzetti. The type strain is CBS 9964 (JCM 13614). All strains were tested for growth on several polysaccharides as sole carbon source. Only some of these polymers supported growth of ascomycetous yeasts. Basidiomycetous yeasts assimilated soluble starch, pullulan, dextran, xylan, polygalacturonate, galactomannan and tannic acid or at least some of these. Cryptococcus podzolicus and T. porosum were the most active in this respect. None of the isolated strains grew on carboxymethyl cellulose, colloidal chitin, arabinogalactan and gum xanthan. Phenolic compounds were assimilated by several strains, belonging to the Trichosporonales and the Microbotryum and Stephanoascus/Blastobotrys clades, but not by members of the Tremellales (Cryptococcus musci excepted) and the Debaryomyces/ Lodderomyces clade. Most of the ascomycetes assimilated n-hexadecane.

Four novel yeasts from decaying organic matter: Blastobotrys robertii sp. nov., Candida cretensis sp. nov., Candida scorzettiae sp. nov. and Candida vadensis sp. nov.

“…Fermentation of sugars was shown only by C. cretensis. In contrast to many basidiomycetous yeasts isolated from rotten wood, ascomycetous yeasts did not exhibit much degradative activity towards phenolic compounds and polysaccharides (Middelhoven 2006). C. cretensis and C. vadensis are notable for assimilation of xylan that supported slow growth of C. scorzettiae and B. robertii.…”

“…Growth on L-malic, D-galactaric (mucic, 2.5 g per litre), D-glucaric (saccharic) and tartaric acids was tested at pH 4.0. Assimilation of non-traditional carbon compounds was studied according to Middelhoven (2006). Ribosomal DNA (rDNA) sequencing and sequence analysis Methods for isolation of nuclear DNA and amplification of LSU rDNA domains 1 and 2 (D1/D2) by the polymerase chain reaction (PCR) were previously given Robnett 1998, 2003).…”

“…The type strain was isolated from rotten oak wood (Quercus robur L.) in Wageningen, The Netherlands, in August 2002 and originally was assigned strain number QuB-82 (Middelhoven 2006). The strain was deposited in two culture collections, viz.…”

“…Recently, two studies have been undertaken. Middelhoven (2004Middelhoven ( , 2006 analysed the yeast flora of two decaying mushrooms as well as that of several samples of rotten wood. In addition to known species, both studies yielded two anamorphic ascomycetous species that could not be identified.…”

Candida cellulosicola sp. nov., a xylose-utilizing anamorphic yeast from rotten wood

“…These yeasts are of potential value in bio-ethanol production from lignocellulose materials. During an ecological survey on microfungi colonizing rotten wood in the rainforest of southern Chile, Dill et al (1984) and Ramírez & González (1984a, b, c) described a total of 18 novel yeast species (Middelhoven, 2006). Of the six novel methanol-assimilating ascomycetous yeast species from wood material described by Péter et al (2003), four were isolated from rotten wood.…”