New yeast species in Okinawan fruit flies with heat resistance up to 35℃ discovered by Osaka University researchers

A research group led by Assistant Professor Taisuke Seike and Professor Fumio Matsuda of the Graduate School of Information Science and Technology at Osaka University, in collaboration with Special Associate Professor Hiroki Takekata of the University of the Ryukyus, Assistant Professor Keiko Kono of Okinawa Institute of Science and Technology Graduate University (OIST) and Team Leader Chikara Furusawa of RIKEN, has discovered a new yeast species, Hanseniaspora Drosophilae sp. nov., from Drosophila in Okinawa. The research revealed that this yeast is clearly distinct from its closest species, including existing Hanseniaspora species, in terms of both genomic information and physiological traits. Specifically, the new species exhibits greater heat tolerance, enhanced ability to assimilate certain carbon sources, and higher drug resistance than its closest relatives. These unique characteristics provide new insights into yeast evolution and taxonomy while also highlighting its potential for various industrial applications, including food fermentation and the development of antimicrobial agents. The study was published in the International Journal of Systematic and Evolutionary Microbiology.

Yeasts of the genus Hanseniaspora play crucial roles in various ecosystems through their interactions with insects and fruit. They are abundant in grapes, and their high fermentation performance has attracted attention in winemaking. However, their evolutionary background and the characteristics of new species have not been studied in detail until now. Focusing on the feeding behavior of Drosophila, which consumes yeast, the research group collected specimens from various regions across Japan over several years and conducted genetic analyses on wild yeasts isolated from them. Specifically, they performed whole genome analysis on the D1/D2 domain and ITS region of rDNA. As a result, they discovered a new yeast species from Drosophila collected on the campuses of the University of the Ryukyus and OIST.

The genome of this yeast is approximately 9.6 Mb in size, with a GC (guanine and cytosine) content of around 26.7%. In contrast, closely related species have a GC content of about 37%, indicating that the new species has a significantly lower GC content than other yeasts in the Hanseniaspora genus. This GC skew suggests that the new yeast species may have undergone a specific environmental or evolutionary adaptation process. The research team also conducted assimilation tests on approximately 50 different carbon and nitrogen sources, along with physiological characterization tests. These analyses revealed that the new yeast species possesses three key characteristics distinguishing it from existing species.

First, the new species has high temperature tolerance, with some strains being able to survive at temperatures as high as 35℃ (a temperature at which growth is restricted in most yeasts). Second, the new species could assimilate carbon sources such as sucrose and raffinose. The efficient utilization of these carbon sources is a very prominent feature among yeasts of this genus. Furthermore, the new species exhibited very high resistance to cycloheximide, an antibiotic with strong antifungal activity against yeasts and filamentous fungi. These characteristics may contribute to industrial applications of the new yeast species, particularly innovations in fermentation processes and bioprocesses. For example, its high temperature tolerance may be useful to reduce cooling costs in the fermentation process, and its ability to assimilate a variety of carbon sources may open a path to develop methods for efficient alcohol fermentation from a wide range of substrates. Its high antimicrobial resistance is expected to help reduce the risk of contamination by other microorganisms during the fermentation process, allowing for stable production.

This yeast has been consistently isolated from Drosophila in Okinawa over multiple years but has not been detected in Drosophila from more than 60 other locations across Japan. Additionally, it has not been found in plants or soils in Okinawa. This suggests that the yeast may have a specific association with Drosophila. This specificity indicates a potential role for Drosophila in the distribution and evolution of yeast, offering valuable insights into yeast evolution, ecology and industrial applications.

Seike stated, "Through this study, I visited Okinawa's natural environments many times, exploring the relationship between yeast and Drosophila on the path to discovering a new yeast species. Each time I uncovered a hidden potential within these yeasts, I was struck by the remarkable diversity and complexity of life. I hope this research will unlock new possibilities for microorganisms and serve as a step toward a more sustainable society."

Journal Information
Publication: International Journal of Systematic and Evolutionary Microbiology
Title: Discovery and identification of a novel yeast species, Hanseniaspora drosophilae sp. nov., from Drosophila in Okinawa, Japan
DOI: 10.1099/ijsem.0.006661