Zygosaccharomyces lentus sp. nov., a new member of the yeast genus Zygosaccharomyces Barker.

Unusual growth characteristics of a spoilage yeast, originally isolated from spoiled whole-orange drink and previously identified as Zygosaccharomyces bailii, prompted careful re-examination of its taxonomic position. Small-subunit rRNA gene sequences were determined for this strain and for four other strains also originally described as Z. bailii but which, in contrast to other strains of this species, grew poorly or not at all under aerobic conditions with agitation, failed to grow in the presence of 1% acetic acid and failed to grow at 30 degrees C. Comparative sequence analysis revealed that these strains represented a phylogenetically distinct taxon closely related to, but distinct from, Z. bailii and Zygosaccharomyces bisporus. Furthermore, sequence analysis of the internal transcribed spacer (ITS) region showed that, while all five strains had identical ITS2 sequences, they could be subdivided into two groups based on ITS1 sequences. Despite such minor inter-strain sequence variation, these yeasts could readily be distinguished from all other currently described Zygosaccharomyces species by using ITS sequences. On the basis of the phylogenetic results presented, a new species comprising the five strains, Zygosaccharomyces lentus sp. nov., is described and supporting physiological data are discussed, including a demonstration that growth of this species is particularly sensitive to the presence of oxygen. The type strain of Z. lentus is NCYC D2627T.