Review Finds Vineyard Microbes Help Give Wines Their Regional Character

A review published July 20 in the journal Applied and Environmental Microbiology says microbes living in vineyards and wineries appear to be an important part of terroir, the set of local factors that gives wines their distinctive character. The paper argues that bacteria, fungi and yeasts linked to a place can help shape fermentation and influence aroma, flavor and other sensory traits, alongside better-known factors such as soil, climate, topography, grape variety and human practices.

The review, written by Lena Flörl, Reid Griggs and Nicholas A. Bokulich, examines research on what scientists call “microbial terroir.” The idea is that regional microbial communities, both before and after harvest, contribute to differences between wines from different places. The authors say the field has moved quickly in the past decade and now includes evidence from all major wine-growing regions, although important questions remain about causation, year-to-year variation and the exact role of individual strains.

The paper traces a turning point to 2014, when DNA sequencing studies began to show that the microbes found on wine grapes varied by region, grape variety and climate. Later work linked regional yeast diversity and the microbiota on grapes before fermentation to differences in wine chemistry. Since then, the review says, many studies have supported the view that these microbial patterns matter not only in wine, but also in other traditional fermented foods such as cheese and cured ham.

The authors stress that microbial terroir does not replace the traditional meaning of terroir. Instead, they describe microbes as one more layer in a larger system. In vineyards, microorganisms move through the environment by wind, insects, animals and human activity. Whether they persist depends on local conditions that select which microbes can survive and grow. That means nearby places can still host different microbial communities, and wines from the same place can show shifts from one vintage to another.

According to the review, soil is a major microbial reservoir in vineyards. It helps repopulate short-lived plant parts such as leaves, flowers and berries each season. Bark also appears to be an important source. Microbes on grape skins matter because they can enter the grape must and help start fermentation as fruit moves from the vineyard to the winery. The review says soil and bark tend to host more stable communities over time, while berries and leaves are more variable because they are exposed to weather, insects and other changing conditions.

The article also describes strong evidence that site-specific environmental conditions are the main driver of differences in vineyard microbiomes. Soil chemistry, pH, slope, altitude, temperature and water availability all appear to influence which microbes dominate. In some cases, the authors note, small differences within a single vineyard can produce more microbial variation than the distance between two vineyards. They say this is one reason researchers must be careful not to treat microbial terroir as something that lines up neatly with human-drawn regional borders.

Year-to-year variation, often raised by critics as a challenge to the theory, is treated in the review as part of the point rather than a contradiction. Wine quality already changes with vintage because weather changes. The authors say microbial communities appear to respond to those same annual shifts. Studies have found that berry microbiomes can differ across vintages, though some regions show less change than others. The review says this makes long-term and repeated sampling essential, especially as climate patterns continue to shift.

The grapevine itself is another factor. Different grape cultivars can host different microbial communities on berries, leaves and roots. Grafting adds more complexity because one vine can combine two genotypes, the rootstock and the scion, which may influence microbial recruitment in different ways. The review says the effect of plant genetics is not fixed and depends on local conditions and the vine’s stage of growth. As berries ripen, for example, their chemistry changes, acidity falls and sugars rise, and the microbial community shifts toward lower diversity and more fermentative organisms.

Human decisions in the vineyard also appear to shape microbial diversity, though the review says the effects are often hard to separate from local environmental conditions. Tillage, cover crops, fertilizers, fungicides, irrigation and even the orientation of vine rows can alter soil conditions, moisture, light or temperature and, in turn, microbial communities. Some studies find direct effects on soil microbes, while links to the microbes on fruit are less consistent. The authors also note that nearby dust, road traffic and other minor disturbances can influence the berry microbiome.

On wine quality, the review says the strongest evidence points to fungi and yeasts as major contributors to regional character. Alcoholic fermentation is driven mainly by yeast, and fungal communities often show clearer geographic patterning than bacteria. Studies of spontaneous fermentations have found that fungal diversity is more closely tied than bacterial diversity to differences in aroma and wine chemistry. The review also highlights the role of non-Saccharomyces yeasts, a broad group of species that can be present early in fermentation and may add aromatic complexity even if they do not dominate by the end.

The paper says Saccharomyces cerevisiae still takes over most wine fermentations, but the starting community matters. Even low-abundance microbes can release compounds or enzymes that affect aroma. Strain-level differences are especially important, the authors say, because different strains of the same species can behave differently in fermentation and produce different sensory outcomes. One problem for researchers is that many studies still rely on sequencing methods that identify organisms only at broad taxonomic levels, making it difficult to separate one strain from another.

The review also expands the idea of terroir beyond the vineyard. Winery surfaces, equipment and indoor conditions can act as reservoirs for microbes that carry over from one batch or one year to the next. Studies cited in the paper suggest that resident winery microbes do not erase the site-specific signature of grapes from different vineyards, but they do influence fermentation. Practices such as adding commercial yeast, using sulfur dioxide, controlling fermentation temperature, cold soaking and sanitation can either suppress or enhance the expression of local microbial communities.

The authors point to practical uses for this line of research, including better control of spoilage, improved fermentation starters and more sustainable vineyard management. They also say more rigorous study designs are needed, especially repeated sampling over time, better attention to vineyard layout and plant age, and newer sequencing methods that can identify microbes and their functions with much higher precision. The paper notes that some of the hardest questions now involve tracing how microbes move between soil, vine, fruit and winery, and measuring how much each stage contributes to the wine that reaches the bottle.