Temporal and Functional Profiling of the Microbiome of High and Low Nitrogen Content Barley Seed in Silo Storage

Barley grain quality is influenced by nitrogen content and storage conditions; however, their impact on the composition and function of the grain microbiome is not well understood. This study combined metataxonomic (16S rRNA and ITS) profiling, metagenome sequencing, and metaproteome analyses to characterize the structure and function of the barley grain microbiome. Grains with high (> 1.5%) and low (< 1.5%) nitrogen content from a single barley cultivar (Kadie) were sampled at harvest and after 3, 6, and 9 months of storage. Amplicon sequencing revealed a community dominated by Proteobacteria, Firmicutes, and Ascomycota, while metagenomics confirmed the abundance of genera such as Erwinia, Pantoea, and Pseudomonas, aligning with previous reports of barley endophytes. While a consistent set of core microbial genera was identified, their relative abundances varied throughout storage. Metagenomic analysis revealed the high-nitrogen grain microbiome had potential for rapid metabolic activity that declined post-harvest, whereas the low nitrogen grain community sustained prolonged metabolic potential. Metaproteomics confirmed that these functional shifts revealed a temporal transition from active growth to stress tolerance. Findings from this work contribute to a better understanding of the barley grain microbiome during prolonged storage, offering insights that could help optimize storage for malting and brewing.