RESUMEN
Annual surveys of Irish soil samples identified three isolates, CBS 16921 (UCD88), CBS 18246 (UCD443), and CBS 18247 (UCD483), of an apiculate yeast species within the Hanseniaspora genus. The internal transcribed spacer (ITS) and D1/D2 region of the large subunit (LSU) rRNA sequences showed that these are isolates of the recently described species Hanseniaspora menglaensis, first isolated from Southwest China. No genome sequence for H. menglaensis is currently available. The genome sequences of the three Irish isolates were determined using short-read (Illumina) sequencing, and the sequence of one isolate (CBS 16921) was assembled to chromosome level using long-read sequencing (Oxford Nanopore Technologies). Phylogenomic analysis shows that H. menglaensis belongs to the fast-evolving lineage (FEL) of Hanseniaspora. Only one MAT idiomorph (encoding MATα1) was identified in all three sequenced H. menglaensis isolates, consistent with one mating type of a heterothallic species. Genome comparisons showed that there has been a rearrangement near MATα of FEL species compared to isolates from the slowly evolving lineage (SEL).
RESUMEN
During a survey of Nothofagus trees and their parasitic fungi in Andean Patagonia (Argentina), genetically distinct strains of Hanseniaspora were obtained from the sugar-containing stromata of parasitic Cyttaria spp. Phylogenetic analyses based on the single-gene sequences (encoding rRNA and actin) or on conserved, single-copy, orthologous genes from genome sequence assemblies revealed that these strains represent a new species closely related to Hanseniaspora valbyensis. Additionally, delimitation of this novel species was supported by genetic distance calculations using overall genome relatedness indices (OGRI) between the novel taxon and its closest relatives. To better understand the mode of speciation in Hanseniaspora, we examined genes that were retained or lost in the novel species in comparison to its closest relatives. These analyses show that, during diversification, this novel species and its closest relatives, H. valbyensis and Hanseniaspora jakobsenii, lost mitochondrial and other genes involved in the generation of precursor metabolites and energy, which could explain their slower growth and higher ethanol yields under aerobic conditions. Similarly, Hanseniaspora mollemarum lost the ability to sporulate, along with genes that are involved in meiosis and mating. Based on these findings, a formal description of the novel yeast species Hanseniaspora smithiae sp. nov. is proposed, with CRUB 1602 H as the holotype.
RESUMEN
Saccharomyces yeast species are currently the most important yeasts involved in industrial-scale food fermentations. However, there are hundreds of other yeast species poorly studied that are highly promising for flavour development, some of which have also been identified in traditional food fermentations. This work explores natural yeast biodiversity in terms of aroma formation, with a particular focus on aromas relevant for industrial fermentations such as wine and beer. Several non-Saccharomyces species produce important aroma compounds such as fusel alcohols derived from the Ehrlich pathway, acetate esters and ethyl esters in significantly higher quantities than the well-known Saccharomyces species. These species are Starmera caribaea, Hanseniaspora guilliermondii, Galactomyces geotrichum, Saccharomycopsis vini and Ambrosiozyma monospora. Certain species revealed a strain-dependent flavour profile while other species were very homogenous in their flavour profiles. Finally, characterization of a selected number of yeast species using valine or leucine as sole nitrogen sources indicates that the mechanisms of regulation of the expression of the Ehrlich pathway exist amongst non-conventional yeast species.