Metagenomic insights into viral dynamics and funcation in Baijiu

Baijiu fermentation represents a sophisticated microbial-driven biochemical process mediated by complex microbial consortium. Despite extensive characterization of bacterial and fungal roles in fermentation systems, the virus remains a critical knowledge gap. In this study,we employed metagenomics to profile the dynamics of viral community in fermented grains across five stages (day 0, 5, 10, 20 and 30) of a Baijiu fermentation. The metagenomics revealed 101 viral families, dominated by Metaviridae, Parvoviridae, Aliceevansviridae, Herelleviridae, Geminiviridae, Iridoviridae, and Genomoviridae, and lactic acid bacteria was identified as primary phage hosts. The results revealed that ssRNA viruses and ssDNA viruses were more abundant during 0-5 days, dsDNA viruses became dominant during 10-30 days. Multivariate analysis indicated that the viral community dynamics during the fermentation were primarily governed by microbes in succession, environmental factors (temperature,pH, moisture and glucose) and metabolites (lactic acid, acetate and ethanol) in the biosystem. Notably, predicting phages exhibited strong positive correlations with their respective hosts (P < 0.01, r > 0.6). We have identified viral auxiliary metabolic genes (AMGs) related to amino acid metabolism and vitamin biosynthesis. At 30 days of fermentation, the number and abundance of AMGs significantly increased. Our findings provide novel insights into the viral ecology in complex Baijiu fermentation ecosystem, shedding light on the intricate interactions within fermentation microbial communities.