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Figure 1. Gut microbiota as a source of B-group vitamins and vitamin K. (A) Occurrence of de novo biosynthetic pathways for B-group vitamins across major gut bacterial phyla, assessed from > 2,000 reference genomes. Error bars indicate 95% Wilson confidence intervals; (B) Relative abundance of individual vitamin biosynthetic pathways in the human gut microbiota, based on > 4,000 adult gut metagenomes. Error bars represent the interquartile range (IQR); (C) Vitamin-specific variability scores across microbial taxa within each taxonomic rank, reflecting diversity in biosynthetic potential, calculated as described by Rodionov et al.^[37]; (D) Schematic illustrating absorption of microbially derived B vitamins in the human colon Vitamin availability is shaped by microbe-microbe interactions (competition and cooperation) and host factors such as age, diet, and geographic origin. Created in BioRender. Mancabelli, L. (2025).