Weissella as a core member of the Gir cow milk microbiome: functional insights

Gir cow (Bos indicus) milk is widely valued for its nutritional quality, digestibility, and A2 β-casein content; however, the microbial determinants contributing to these attributes remain insufficiently characterized. In this study, dominant lactic acid bacteria (LAB) associated with Gir cow milk were isolated and evaluated using an integrated phenotypic and genome-based approach to elucidate their functional relevance. Raw milk samples were analyzed to isolate LAB, which were characterized through morphological, biochemical, and molecular analyses. Predominant isolates were identified as Weissella cibaria and Weissella confusa. Selected isolates exhibited strain-dependent tolerance to acidic pH, bile salts, and phenolic stress, along with auto-aggregation ability, cholesterol assimilation, and antagonistic activity against enteric pathogens. Survival under simulated gastrointestinal conditions was further validated by viable cell count analysis. Whole-genome sequencing of W. cibaria revealed a high-quality draft genome of approximately 2.43 Mb with a GC content of 44.97%, assembled into 21 contigs, encoding 2,282 protein-coding sequences, 11 rRNA genes, and 72 tRNA genes. Functional annotation indicated enrichment of genes associated with carbohydrate metabolism, stress adaptation, and membrane transport, while screening confirmed the absence of known virulence determinants and transferable antibiotic resistance genes, supporting its safety profile. The consistent predominance of Weissella spp. in Gir cow milk suggests a breed-associated microbial signature that may contribute to the functional characteristics of this indigenous dairy system. Collectively, these findings position Weissella as a promising functional component of the Gir cow milk microbiome and provide a genomic framework supporting its potential application in probiotic and functional dairy research.