Metschnikowia okinawaensis sp. nov. and Metschnikowia ryukyuensis sp. nov., two novel yeast species isolated from flowers and young fruits in Okinawa, Japan.

Two novel yeast species belonging to the genus Metschnikowia were isolated from flowers and young fruits in Okinawa, Japan. Five strains (JCM 35539, JCM 36740T, JCM 36743, JCM 36744, and JCM 36747) and four strains (JCM 35542, JCM 35544T, JCM 36745, and JCM 38279) were repeatedly isolated from samples collected over 2-3 y. Because BLAST analysis of D1/D2 large subunit ribosomal DNA sequences did not clearly resolve their phylogenetic placement and intragenomic polymorphisms were detected in the internal transcribed spacer region, their relationships were further assessed by whole-genome phylogenetic analysis using available genome data from Metschnikowia and related taxa. This analysis showed that the two novel species formed a distinct clade with Candida danieliae, the closest among described species in the dataset. Analysis of MAT-locus gene collinearity revealed that each novel species possessed strains of opposite mating types, and mating assays between compatible strains produced elongated asci containing needle-shaped ascospores, which is a characteristic feature of the genus Metschnikowia. By integrating phylogenomic, mating, morphological, and physiological evidence, we conclude that these strains represent two novel yeast species, for which the names Metschnikowia okinawaensis sp. nov. and Metschnikowia ryukyuensis sp. nov. are proposed.