Characterization of the medically important yeast Trichosporon mucoides and its close sister Trichosporon dermatis by traditional and advanced technologies.

Trichosporon dermatis is a causative agent of several mycoses in immunocompromised patients but is often misidentified as Trichosporon mucoides due to their phenotypic resemblance. In order to evaluate the current identification keys for these species and to develop a rapid and reliable identification method, 11 strains of these yeasts were fully characterized in this study by traditional and advanced technologies. DNA sequences of the internal transcribed spacer (ITS), IGS1, and D1/D2 regions identified six of the yeasts as T. dermatis that were previously known as T. mucoides, including ATCC 204094 that has been used as the quality-control strain of T. mucoides for the VITEK 2 system and other commercial yeast identification kits. These two species could not be differentiated reliably by any previously known phenotypic keys for the species, such as growth patterns on ethylamine, phloroglucinol and tyramine, or by the VITEK 2 system. On the other hand, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) proved to be a rapid and reliable identification tool for the two closely related yeasts. With newly added superspectra from fully authenticated reference strains, the VITEK MS system using MALDI-TOF MS successfully separated strains of T. dermatis and T. mucoides at a similarity level of approximately 67 % for the mass spectra data, and could identify these strains at the species level with 100 % accuracy in repeated tests. Furthermore, the in vitro susceptibility results indicated that itraconazole, posaconazole and voriconazole were more effective against both T. mucoides and T. dermatis than the other antifungal agents tested in this study.

Scheffersomyces parashehatae f.a., sp. nov., Scheffersomyces xylosifermentans f.a., sp. nov., Candida broadrunensis sp. nov. and Candida manassasensis sp. nov., novel yeasts associated with wood-ingesting insects, and their ecological and biofuel implications.

During a survey of yeasts associated with wood-ingesting insects, 69 strains in the Scheffersomyces clade and related taxa were isolated from passalid and tenebrionid beetles and the decayed wood inhabited by them. The majority of these yeasts was found to be capable of fermenting xylose, and was recognized as Scheffersomyces stipitis or its close relative Scheffersomyces illinoinensis, which are known to be associated with wood-decaying beetles and rotten wood. Yeasts in 'Scheffersomyces' ( = Candida) ergatensis and 'Scheffersomyces' ( = Candida) coipomoensis were also frequently isolated. The remaining six strains were identified as representing four novel species in the genera Scheffersomyces and Candida based on multilocus sequence analyses of nuclear rRNA genes and four protein-coding genes, as well as other taxonomic characteristics. Two xylose-fermenting species, Scheffersomyces parashehatae f.a., sp. nov. (type strain ATCC MYA-4653(T) = CBS 12535(T) = EH045(T); MycoBank MB805440) and Scheffersomyces xylosifermentans f.a., sp. nov. (type strain ATCC MYA-4859(T) = CBS 12540(T) = MY10-052(T); MycoBank MB805441), formed a clade with Scheffersomyces shehatae and related Scheffersomyces species. Interestingly, S. xylosifermentans can survive at 40 °C, which is a rare property among xylose-fermenting yeasts. Candida broadrunensis sp. nov. (type strain ATCC MYA-4650(T) = CBS 11838(T) = EH019(T); MycoBank MB805442) is a sister taxon of C. ergatensis, while Candida manassasensis sp. nov. (type strain ATCC MYA-4652(T) = CBS 12534(T) = EH030(T); MycoBank MB805443) is closely related to Candida palmioleophila in the Candida glaebosa clade. The multilocus DNA sequence comparisons in this study suggest that the genus Scheffersomyces needs to be circumscribed to the species near S. stipitis (type species) and S. shehatae that can be characterized by the ability to ferment xylose.

Viability of fastidious Phytophthora following different cryopreservation treatments.

Living stock cultures with constant phenotypes and genotypes are required for a wide range of research and industrial applications; however, long-term, stable preservation of fastidious Phytophthora strains has been challenging. In this study, we systematically evaluated different cryopreservation treatments to identify and clarify freezing, thawing, and other conditions appropriate for long-term maintenance. Optimal preservation conditions were largely strain-specific, with robust strains remaining fully viable and the fastidious yielding lower recovery under all test conditions. Nevertheless, several procedures were shown to be generally applicable for effective cryopreservation of most Phytophthora organisms. Fastidious strains retained higher viability following the -1 °C min(-1) freezing protocol (Mr Frosty's) than either of two widely used programmed freezing procedures. Revival was higher when frozen mycelium plugs were thawed at 37 °C for 2 min or 25 °C for 5 min, while lower viability was apparent for fastidious strains thawed at 55 °C for 1.5 min. Among 15 cryoprotective solutions assessed, 5 % dimethyl sulfoxide produced the highest viability for all fastidious strains. The effect of prefreeze and postfreeze treatments on revival was mild, if any, and strain-dependent. This study has generated reliable, practical, long-term preservation solutions applicable to a majority of Phytophthora species. It also has revealed a need for in-depth physiological and morphological investigations to further enhance the preservation methods for fastidious strains.

Yeasts in the Sugiyamaella clade associated with wood-ingesting beetles and the proposal of Candida bullrunensis sp. nov.

During a survey of yeasts associated with wood-ingesting insects, six strains of the Sugiyamaella clade were isolated from the gut of passalid and tenebrionid beetles and the decayed wood inhabited by them. Phylogeny based on rRNA gene sequences placed these yeasts as members of Sugiyamaella smithiae, Sugiyamaella americana, Candida lignohabitans and a novel species closely related to Su. americana. The only strain of the novel species, EH008(T), could be unquestionably distinguished from its relatives by DNA sequences and other taxonomic characteristics. Ascospore production was not observed under the laboratory conditions tested. Therefore, this novel species is proposed as Candida bullrunensis sp. nov. (type strain EH008(T) = ATCC MYA-4660(T) = CBS 11840(T)).