Temporal and spatial dynamics within the fungal microbiome of grape fermentation.

Over 6 years, we conducted an extensive survey of spontaneous grape fermentations, examining 3105 fungal microbiomes across 14 distinct grape-growing regions. Our investigation into the biodiversity of these fermentations revealed that a small number of highly abundant genera form the core of the initial grape juice microbiome. Consistent with previous studies, we found that the region of origin had the most significant impact on microbial diversity patterns. We also discovered that certain taxa were consistently associated with specific geographical locations and grape varieties, although these taxa represented only a minor portion of the overall diversity in our dataset. Through unsupervised clustering and dimensionality reduction analysis, we identified three unique community types, each exhibiting variations in the abundance of key genera. When we projected these genera onto global branches, it suggested that microbiomes transition between these three broad community types. We further investigated the microbial community composition throughout the fermentation process. Our observations indicated that the initial microbial community composition could predict the diversity during the early stages of fermentation. Notably, Hanseniaspora uvarum emerged as the primary non-Saccharomyces species within this large collection of samples.

Recombination, admixture and genome instability shape the genomic landscape of Saccharomyces cerevisiae derived from spontaneous grape ferments.

Cultural exchange of fermentation techniques has driven the spread of Saccharomyces cerevisiae across the globe, establishing natural populations in many countries. Despite this, Oceania is thought to lack native populations of S. cerevisiae, only being introduced after colonisation. Here we investigate the genomic landscape of 411 S. cerevisiae isolated from spontaneous grape fermentations in Australia across multiple locations, years, and grape cultivars. Spontaneous fermentations contained highly recombined mosaic strains that exhibited high levels of genome instability. Assigning genomic windows to putative ancestral origin revealed that few closely related starter lineages have come to dominate the genetic landscape, contributing most of the genetic variation. Fine-scale phylogenetic analysis of loci not observed in strains of commercial wine origin identified widespread admixture with European derived beer yeast along with three independent admixture events from potentially endemic Oceanic lineages that was associated with genome instability. Finally, we investigated Australian ecological niches for basal isolates, identifying phylogenetically distinct S. cerevisiae of non-European, non-domesticated origin associated with admixture loci. Our results illustrate the effect commercial use of microbes may have on local microorganism genetic diversity and demonstrates the presence of non-domesticated, potentially endemic lineages of S. cerevisiae in Australian niches that are actively admixing.

Discovering the indigenous microbial communities associated with the natural fermentation of sap from the cider gum Eucalyptus gunnii.

Over the course of human history and in most societies, fermented beverages have had a unique economic and cultural importance. Before the arrival of the first Europeans in Australia, Aboriginal people reportedly produced several fermented drinks including mangaitch from flowering cones of Banksia and way-a-linah from Eucalyptus tree sap. In the case of more familiar fermented beverages, numerous microorganisms, including fungi, yeast and bacteria, present on the surface of fruits and grains are responsible for the conversion of the sugars in these materials into ethanol. Here we describe native microbial communities associated with the spontaneous fermentation of sap from the cider gum Eucalyptus gunnii, a Eucalyptus tree native to the remote Central Plateau of Tasmania. Amplicon-based phylotyping showed numerous microbial species in cider gum samples, with fungal species differing greatly to those associated with winemaking. Phylotyping also revealed several fungal sequences which do not match known fungal genomes suggesting novel yeast species. These findings highlight the vast microbial diversity associated with the Australian Eucalyptus gunnii and the native alcoholic beverage way-a-linah.