Discovery and identification of a novel yeast species, Hanseniaspora drosophilae sp. nov., from Drosophila in Okinawa, Japan

Abstract

Hanseniaspora, a genus of yeasts in which many species reproduce sexually, has attracted the attention of researchers because of its prevalence in diverse ecological niches. Building on our extensive collection efforts since 2020, three previously unknown yeast strains from wild Drosophila species trapped in ripe bananas in Okinawa, Japan, were isolated. Using a multifaceted approach, including physiological assessments and sequence analysis of the D1/D2 domain of the 26S LSU rRNA gene and the internal transcribed spacer (ITS) region, it was revealed that these strains are novel members of the genus Hanseniaspora. The three strains, JCM 36741^T, JCM 36742 and JCM 36748, had identical sequences in their respective D1/D2 and ITS regions, justifying their classification as a single species. Moreover, the new species exhibited a remarkable degree of sequence divergence from its closest relatives, differing by 7 nucleotide substitutions (1.28%) in the D1/D2 domain, 29 nucleotide substitutions and 4 gaps (4.08%) in the ITS regions. These substantial sequence differences highlight the distinctiveness of this novel species in the genus Hanseniaspora. Further analysis revealed physiological characteristics that distinguished the new species from its closest relative, Hanseniaspora hatyaiensis (nom. inval.). These findings culminated in the proposed name Hanseniaspora drosophilae sp. nov., which recognizes the unique ecological niche within the Drosophila microbiota. By uncovering this novel species, this study not only adds to the growing body of knowledge on yeast diversity but also sheds light on the intricate ecological relationships that shape microbial communities. The implications of this discovery extend beyond taxonomic boundaries, inviting further exploration of the evolutionary dynamics and ecological significance of yeast-fly interactions. We propose accommodating H. drosophilae sp. nov. in the genus Hanseniaspora with JCM 36741^T as the holotype. The MycoBank accession number is MB 853822.

Keywords: Drosophila; Hanseniaspora drosophilae sp. nov.; Japan; Okinawa; yeasts.

Fig. 1.. Phylogenetic tree of Hanseniaspora drosophilae sp. nov. and related species based on NJ analysis of the concatenated sequences of the ITS and D1/D2 domain of the LSU rRNA gene. The tree was constructed using the NJ method in the mega X software (v10.1.8). The numbers on the branches represent the frequencies with which a given branch appeared in the 10 000 bootstrap replicates. Bootstrap values >50% are shown. Wickerhamomyces anomalus CBS 5759^T (NR_111210/KY110078) was selected as the outgroup. Scale bar, 0.020 substitutions per site.

Fig. 2.. Microscopic observation of the novel yeast species. (a) Banana trap to collect Drosophila species and (b) budding cells of H. drosophilae sp. nov. JCM 36741^T on YM agar after 3 days at 25 °C. Cells are lemon-shaped. (c) Ascospores (arrow) of JCM 36741^T on YMoA after 1 week. Scale bar, 20 µm.