A Shotgun Metagenomic Sequencing Exploration of Cabernet Sauvignon Grape Must Reveals Yeast Hydrolytic Enzymes
Abstract
Shotgun sequencing was employed to explore the community structure (phylotyping of rRNA genes) and
functional potential of Cabernet Sauvignon grape must microbiome. A metagenomic library, representing
92.6 Mb of genetic information, was generated from DNA obtained from Cabernet Sauvignon grape
must.. Fungi were identified as the dominant domain (59.5%) followed by Streptophyta (39%). Among
the 84 fungal species, 22 were yeasts of various genera. Additionally, grapevine endophytes such as
Davidiella sp., Botryotinia fuckeliana, Alternaria sp., and Cladosporium sp. were identified. An unusually
high prevalence of Mucor spp. was evidenced. Functional annotation revealed sequences of genes
involved in metabolism (35.6%), followed by poorly characterized categories (28.3%), cellular processes
and signalling (18.4%), and finally information storage (17.8%). Among the former, glycosidases were
abundant followed by glycogen debranching enzyme, 6-phosphofructokinase and trehalose-6-phosphate
synthase. Furthermore, the taxonomic analysis of the functional sequence data exhibited the eukaryotic
gene pool that predominantly contains sequences derived from Streptophyta (mainly Vitis vinifera) 60% >
Ascomycota (32%) > Basidiomycota (5%) > Bacteria (2.5%). Finally, sequences of a variety of hydrolytic
enzymes of potential oenological relevance were retrieved, thereby confirming that grape juice is a rich
reservoir for valuable biocatalysts that should be explored further.
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