Begerowomyces aurantius sp. nov., a novel yeast isolated from koalas' habitat in a Japanese zoological park

Abstract

Koalas are iconic mammals indigenous to Australia. These rare animals and their habitats are occasionally associated with pathogenic fungi, including species of Cryptococcus, and consequently, monitoring the mycobiota of areas inhabited by koalas is of considerable importance. In this report, we describe a novel basidiomycetous yeast isolated from a site in Kanazawa Zoo, Japan, associated with captive koalas. Swab samples were collected from koala breeding environments, from which we isolated a novel unencapsulated yeast characterized by ovoid to ellipsoidal cells (3.2-4.9 × 3.5-5 μm). These cells were observed to undergo polar budding and grow as parent bud pairs, with an optimal growth temperature of 28°C. Colonies grown on yeast extract peptone dextrose agar at 28°C have a characteristic coral pink color. On the basis of physiological, morphological, and molecular characters, the new species was placed in the genus Begerowomyces, and the name Begerowomyces aurantius JCM33898^T(LSEM1333^T=CBS16241^T) is proposed.

Keywords: Begerowomyces; breeding environment; koala; novel yeast.

Fig. 1.

The phylogeny of Begerowomyces aurantius based on the 28S rDNA D1/D2 domain. The evolutionary history of B. aurantius was inferred using the Maximum Likelihood method based on sequences of the 28S rDNA D1/D2 domains of 30 species. Bootstrap values lower than 50% are not shown. All positions with less than 95% site coverage were eliminated. A discrete Gamma distribution was used to model evolutionary rate differences among sites [5 categories (+G, parameter=0.1805)].

Fig. 2.

The phylogeny of Begerowomyces aurantius based on the ITS1/ITS4 regions. The evolutionary history of B. aurantius was inferred using the Maximum Likelihood method based on sequences of the ITS1/ITS4 regions of 29 species. Bootstrap values lower than 50% are not shown. All positions with less than 95% site coverage were eliminated. A discrete Gamma distribution was used to model evolutionary rate differences among sites [5 categories (+G, parameter=0.2174)].

Fig. 3.

Microscopy of the Begerowomyces aurantius. (a) Cells were grown on yeast extract peptone dextrose (YPD) agar for 3 days at 28°C; Bar, 5 µm. (b) A scanning electron micrograph of cells showing polar budding of ovoid to ellipsoidal cells. Cells were grown in YPD broth for 24 hr at 28°C with shaking at 160 rpm before being processed for scanning electron microscopy. Bar, 1 µm.

Fig. 4.

Optimal growth temperature of Begerowomyces aurantius. Serial dilutions (OD₆₀₀=1, 0.1, 0.01, and 0.001) of the yeast were spotted onto the surface of YPD agar. The photographs show 3-day-old cultures.

Fig. 5.

Representative matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) spectra of Begerowomyces aurantius.