Grapevine Microbiomics: Bacterial Diversity on Grape Leaves and Berries Revealed by High-Throughput Sequence Analysis of 16S rRNA Amplicons

We used the culture-independent method of high-throughput pyrosequencing of 16S ribosomal RNA (rRNA) gene amplicons to analyze the diversity of bacteria associated with the leaf and berry surfaces of 'Chardonnay' grape in a vineyard close to harvest. Combined, more than half of all bacterial sequences were classified as Proteobacteria. Other well-represented phyla were the Firmicutes, Bacteroidetes, and Actinobacteria. The most abundantly represented genera were Sphingomonas, Hymenobacter, Bacillus, Pseudomonas, Skermanella, Leuconostoc, Massilia, Methylobacterium, Cellvibrio, and Curtobacterium. Together, these top 10 genera accounted for almost one-third of all sequences. We observed differences in the composition of bacterial communities between leaves and berries. Members of the genera Sphingomonas, Hymenobacter and Methylobacterium were abundant on foliage, whereas Achromobacter, Flavobacterium and Cellvibrio were typical for the fruit. Moreover, certain Pseudomonas species appeared to associate exclusively with leaf surfaces, while others were found more frequently on berries. Unanticipated was the discovery of a novel Proteobacterium that dominated the bacterial community on berry surfaces. Our results form the basis for future investigations into the relationship between the structure of microbial communities on grape leaves and berries and the ecosystem (dis)services that these communities provide to grape growers at different pre- and post-harvest stages of production.