Do bacteria affect the quality of wine?

EMBARGOED UNTIL: Monday 5/20, 3 PM MDT

(Symposium Session 147)

Iratxe Zarraonaindia
Argonne National Laboratory
Lemont, chicago, IL, United States
Phone: 6302525007
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Grapevine is a widely cultivated fruit crop with high economic relevance, bringing >$30 B/yr into the US economy and employing ~30,000 people. It is broadly accepted that microbes living in soil surrounding the roots, on/inside plant roots and organs impact in the health and productivity of plants. We have shown that the bacterial communities that live on the flowers, leaves and grapes of merlot plants are very different from those living in the soil and on the roots. These above ground organs are poor in nutrients and suffer from acute temperature/humidity changes and UV light irradiation in contrast to the comparatively weak abiotic condition changes prevailing the root surrounding soils. Taxa surviving/adapted in this harsh above ground niches belonged to Sphingomonas, Pseudomonas, and Enterobacteria. Sphingomonas has been suggested to contribute to plant health by suppressing disease symptoms and Pseudomonas seem to promote biofilm-like structures on grape surfaces, which might protect bacteria from water stress and bactericides. In addition, Enterobacter might play a role in wine flavor/composition as has been reported to be resistant to wine fermentation being prevalent in all the stages of winemaking. As previously reported by other authors, the bacteria living on the flowers, leaves and grapes showed high variability within plant replicates making it difficult to find clear patterns, but the microbes in the soil and roots did showed differences related to the soil type or the clonal variety of the plant. Strikingly, the bacteria associated with the roots of clones 6 and 181 were very different when compared to clones 1 and 3, and interestingly, the flavor and complexity of the wines from those clones are very different to clones 1 and 3. We hypothesize that the bacteria living on the roots of the plants are providing metabolites to the plant that affect the complexity and flavor of the grapes; e.g some denitrifying members of Acidobacteria (e.g genera Koribacteraceae) are significantly more abundant in clone 181 roots which might has its impact in the flavor of the wine, however, this waits to be tested. If true, this could affect the way in which viticulture is performed, by including bacteria in the goal to create the complex flavors that we crave in fine wines.

This project is a collaborative study between Argonne National Laboratory/University of Chicago, The Research Triangle Institute (RTI) International in North Carolina and the Sparkling Pointe wineries in Southold New York. The study is embedded in the Earth Microbiome Project (http://www.earthmicrobiome.org) led by Jack A. Gilbert (Argonne National Laboratory), Rob Knight (University of Colorado) and Janet Janssen (Lawrence Berkeley National Laboratory), which is a multidisciplinary effort to characterize the global microbial taxonomic and functional diversity.

Studies conducted in Arabidopsis, Potato, Poplar etc. revealed that the composition and abundances of bacteria interacting with plants varies with edaphic factors (e.g soil type) and plant species. Interestingly, winemaking industry has been selectively growing cultivars with different traits (grape size, shape, color, flavor, yield of fruit etc) for a long time. In addition, old varieties such as Merlot, Cabernet Sauvignon, Chardone etc. contain many different clonal types that can differ considerably in their viticultural characteristics and so can be exploited to improve the yield. The present study aims to characterize the bacteria that are associated with grapevines and how these bacterial communities change between clonal varieties of Merlot, different soil types, and over time. We characterized the bacteria that lived with these plants by using a powerful sequencing technology (Illumina) to sequence a gene from each bacterium that enables us to identify the species name. We characterized the abundance of each species in 480 samples collected over different seasons from the bulk soil, root zone, roots, leaves and flowers/grapes of 4 Merlot clonal varieties (Clone 1, 3, 6 and 181) growing in 2 soil types (Raven and Riverhead) in Long Island, NY. This project represents the first attempt to determine whether the bacteria that live with grapevines have any relationship to the productivity of the vines and quality of the wine. This work will potentially leading to novel synthetic biology solutions for increasing plant productivity and disease suppression.