Review links vineyard microbiomes to wine’s regional character

Microbes as a layer of terroir

A review published on July 20 in Applied and Environmental Microbiology identifies microorganisms living in vineyards and wineries as a potentially important element of terroir. Authors Lena Flörl, Reid Griggs and Nicholas A. Bokulich argue that place-associated bacteria, fungi and yeasts can help shape fermentation and affect aroma, flavor and other sensory characteristics alongside soil, climate, topography, grape variety and human practices.¹

The review examines “microbial terroir”: the proposition that regional microbial communities present before and after harvest contribute to differences among wines from different places. Research has expanded rapidly over the past decade and now covers all major wine-growing regions, but the authors say causal relationships, changes between years and the functions of individual strains remain insufficiently understood.¹

The authors identify 2014 as a turning point, when DNA-sequencing studies showed that microorganisms on wine grapes varied with region, cultivar and climate. Subsequent studies connected regional yeast diversity and pre-fermentation grape microbiota with differences in wine chemistry. Comparable microbial patterns have also been reported in traditional fermented foods including cheese and cured ham.¹

Microbial terroir is presented as an addition to, rather than a replacement for, the established concept of terroir. Wind, insects, animals and human activity move microorganisms through vineyards, while local conditions determine which ones persist. Consequently, neighboring sites may support distinct communities, and the microbiome of one location may change between vintages.¹

Where vineyard communities originate and how they vary

Soil is described as a major vineyard reservoir that replenishes seasonal plant structures such as leaves, flowers and berries; vine bark is another important source. Organisms on grape skins can enter the must and participate in the beginning of fermentation as harvested fruit reaches the winery. Communities in soil and bark tend to remain more stable over time than those on berries and leaves, which are more exposed to weather, insects and other variable influences.¹

The strongest evidence reviewed attributes differences among vineyard microbiomes primarily to site-specific environmental conditions. Soil chemistry and pH, slope, altitude, temperature and water availability can all affect which organisms dominate. Variation between small areas of the same vineyard can sometimes exceed that between two separate vineyards, so microbial patterns do not necessarily correspond to administrative or human-defined regional boundaries.¹

The review treats vintage variation as an expected feature of microbial terroir rather than evidence against it. Just as changing weather affects wine quality from year to year, microbial communities respond to annual conditions. Berry microbiomes have differed among vintages in some studies, although the degree of change varies by region. The authors therefore call for repeated, long-term sampling, particularly as climate patterns shift.¹

Grapevine genetics also contribute to microbial variation. Cultivars may support different communities on their berries, leaves and roots, while grafted vines combine a rootstock and scion whose genotypes may recruit microorganisms differently. These genetic effects depend on the environment and the vine’s growth stage. During ripening, declining acidity and rising sugar levels are accompanied by lower microbial diversity and a shift toward organisms associated with fermentation.¹

Vineyard management may alter microbial diversity, although its effects can be difficult to distinguish from environmental influences. Tillage, cover crops, fertilizers, fungicides, irrigation and row orientation can change soil, moisture, light or temperature. Direct effects on soil communities appear in some studies, but evidence concerning fruit-associated microbes is less consistent. Dust, road traffic and other localized disturbances may also affect berry microbiomes.¹

Fermentation, wineries and wine character

Fungi and yeasts provide the strongest evidence for a microbial contribution to regional wine character. Yeasts conduct most alcoholic fermentation, and fungal communities often display clearer geographical patterns than bacterial communities. In spontaneous fermentations, fungal diversity has shown closer associations with aroma and wine chemistry than bacterial diversity. Non-Saccharomyces yeasts may contribute aromatic complexity early in fermentation even when they are no longer dominant at its conclusion.¹

Saccharomyces cerevisiae ultimately dominates most wine fermentations, but the initial microbial population can still affect the result. Organisms present in small numbers may release aroma-active compounds or enzymes, and strains within the same species can behave differently and produce distinct sensory effects. Many sequencing methods identify microorganisms only at broader taxonomic levels, limiting researchers’ ability to distinguish these strain-specific roles.¹

The review extends microbial terroir into the winery, where surfaces, equipment and indoor conditions can preserve communities between batches or years. The cited studies indicate that resident winery organisms influence fermentation without necessarily eliminating the vineyard-specific signature carried by grapes. Commercial yeast inoculation, sulfur dioxide, fermentation-temperature control, cold soaking and sanitation may suppress or support the expression of local microbial communities.¹

Research and practical applications

Potential applications include better spoilage control, improved fermentation starters and more sustainable vineyard management. The authors call for stronger study designs with repeated sampling, closer consideration of vineyard layout and vine age, and sequencing methods capable of identifying microorganisms and their functions more precisely. Major unresolved questions include how microbes travel among soil, vines, fruit and wineries, and how much each stage contributes to the finished bottled wine.¹