Asterotremella gen. nov. albida, an anamorphic tremelloid yeast isolated from the agarics Asterophora lycoperdoides and Asterophora parasitica

Skin Mycobiota of the Captive Giant Panda (Ailuropoda melanoleuca) and the Distribution of Opportunistic Dermatomycosis-Associated Fungi in Different Seasons

Dermatomycosis is the second major cause of morbidity in giant pandas (Ailuropoda melanoleuca), and seriously endangers its health. Previous observations indicated that the occurrence of dermatomycosis in the giant panda varies in different seasons. The skin microbiota is a complex ecosystem, but knowledge on the community structure and the pathogenic potentials of fungi on the skin of the giant panda remains limited. In this study, samples from the giant panda skin in different seasons were collected, and the mycobiota were profiled by 18S rRNA gene sequencing. In total, 375 genera in 38 phyla were detected, with Ascomycota, Basidiomycota, Streptophyta, and Chlorophyta as the predominant phyla and Trichosporon, Guehomyces, Davidiella, Chlorella, Asterotremella, and Klebsormidium as the predominant genera. The skin mycobiota of the giant panda changed in the seasons, and the diversity and abundance of the skin fungi were significantly higher in spring, autumn, and summer than in the winter. Several dermatomycosis-associated fungi were detected as opportunists in the skin mycobiota of healthy giant pandas. Clinical dermatomycosis in the giant panda is observed more in summer and autumn. In this study, the results indicated that the high diversity and abundance of the skin fungi may have enhanced the occurrence of dermatomycosis in autumn and summer, and that dermatomycosis-associated fungi are the normal components of the skin mycobiota.

Advances in yeast systematics and phylogeny and their use as predictors of biotechnologically important metabolic pathways

Detection, identification and classification of yeasts have undergone a major transformation in the last decade and a half following application of gene sequence analyses and genome comparisons. Development of a database (barcode) of easily determined DNA sequences from domains 1 and 2 (D1/D2) of the nuclear large subunit rRNA gene and from ITS now permits many laboratories to identify species quickly and accurately, thus replacing the laborious and often inaccurate phenotypic tests previously used. Phylogenetic analysis of gene sequences is leading to a major revision of yeast systematics that will result in redefinition of nearly all genera. This new understanding of species relationships has prompted a change of rules for naming and classifying yeasts and other fungi, and these new rules are presented in the recently implemented International Code of Nomenclature for algae, fungi, and plants (Melbourne Code). The use of molecular methods for species identification and the impact of Code changes on classification will be discussed, as will use of phylogeny for prediction of biotechnological applications.

Towards an integrated phylogenetic classification of the Tremellomycetes

Families and genera assigned to Tremellomycetes have been mainly circumscribed by morphology and for the yeasts also by biochemical and physiological characteristics. This phenotype-based classification is largely in conflict with molecular phylogenetic analyses. Here a phylogenetic classification framework for the Tremellomycetes is proposed based on the results of phylogenetic analyses from a seven-genes dataset covering the majority of tremellomycetous yeasts and closely related filamentous taxa. Circumscriptions of the taxonomic units at the order, family and genus levels recognised were quantitatively assessed using the phylogenetic rank boundary optimisation (PRBO) and modified general mixed Yule coalescent (GMYC) tests. In addition, a comprehensive phylogenetic analysis on an expanded LSU rRNA (D1/D2 domains) gene sequence dataset covering as many as available teleomorphic and filamentous taxa within Tremellomycetes was performed to investigate the relationships between yeasts and filamentous taxa and to examine the stability of undersampled clades. Based on the results inferred from molecular data and morphological and physiochemical features, we propose an updated classification for the Tremellomycetes. We accept five orders, 17 families and 54 genera, including seven new families and 18 new genera. In addition, seven families and 17 genera are emended and one new species name and 185 new combinations are proposed. We propose to use the term pro tempore or pro tem. in abbreviation to indicate the species names that are temporarily maintained.

Basidiomycetous yeasts from boletales fruiting bodies and their interactions with the mycoparasite Sepedonium chrysospermum and the host fungus Paxillus

Interactions between mushrooms, yeasts, and parasitic fungi are probably common in nature, but are rarely described. Bolete fruiting bodies are associated with a broad spectrum of microorganisms including yeasts, and they are commonly infected with filamentous mycoparasites of the genus Sepedonium (teleomorph Hypomyces). We report the isolation of 17 yeast strains from Paxillus and Xerocomus, 16 of which were obtained from the surface tissue, the primary site of Sepedonium infection. Phylogenetic analyses with the D1/D2 region of the 28S ribosomal gene and the internal transcribed spacers placed the yeasts as Rhodotorula, Rhodosporidium, and Mastigobasidium from the Pucciniomycotina, Cryptococcus, Cystofilobasidium, Holtermanniella, and Trichosporon from the Agaricomycotina, and Kluyveromyces from the Saccharomycotina including the first isolation of Rhodotorula graminis from Europe. To investigate the influence of the yeast strains on the mycoparasite and the host fungus, in vitro assays were conducted with Sepedonium chrysospermum and Paxillus involutus. Both S. chrysospermum growth inhibitory and stimulating yeast strains were detected among the isolates. The number of S. chrysospermum inhibitory yeast strains increased and the number of S. chrysospermum stimulatory yeast strains decreased in the presence of P. involutus in co-cultures. Low nutrient levels in the culture medium also led to an increased number of S. chrysospermum inhibitory yeast strains and ten yeasts inhibited the mycoparasite in spatial separation by a crosswall. Six yeast strains inhibited P. involutus in dual culture, and the inhibitory P. involutus yeast interactions increased to nine in the presence of S. chrysospermum. Our results suggest that the bolete-associated yeasts influence the growth of the mycoparasitic fungus, which may affect the health of the fruiting bodies.

Cryptococcus thermophilus sp. nov., isolated from cassava sourdough

A novel anamorphic yeast, strain LTH 6662(T), was isolated from cassava sourdough. The isolate supposedly originated from cassava flour or was a contaminant thereof. Sequencing of the D1/D2 domain of the 26S rRNA gene indicated that strain LTH 6662(T) represents a novel species. Its closest relatives were members of the Cryptococcus humicola complex. The novel strain had several physiological characteristics that differed from those of related species: the ability to assimilate raffinose and cadaverine; the inability to assimilate soluble starch, xylitol, galactitol, butane-2,3-diol, sodium nitrite and lysine; the ability to grow without vitamins and at 42 °C; and the inability to produce starch-like substances. Its major ubiquinone was Q-10. In addition, buds were formed on small neck-like structures. In liquid medium, green or blue fluorescent substances were produced. The name Cryptococcus thermophilus sp. nov. is proposed, with LTH 6662(T) (=DSM 19443(T)=CBS 10687(T)) as the type strain.

Asterotremella meifongana sp. nov. and Asterotremella nantouana sp. nov., two anamorphic basidiomycetous yeasts isolated from soil and mushrooms

Two novel yeast species, Asterotremella meifongana sp. nov. and Asterotremella nantouana sp. nov., belonging to Asterotremellaceae within the Trichosporonales, are proposed to accommodate five strains isolated from Taiwanese samples of soil and basidiocarps during 2006-2007. Sequence analysis of the D1/D2 domains of the large subunit rRNA gene revealed that the two species are phylogenetically closely related to species of the genus Asterotremella, which indicates that they are members of the genus. The two species can be further differentiated from other Asterotremella species based on their internal transcribed spacer sequences, as well as on a few physiological test responses. The type strains are A. meifongana SN4S04(T) (=CBS 11424(T) = BCRC 23196(T)) and A. nantouana SN5S06(T) (=CBS 10890(T) = BCRC 23135(T)).