Genes for Vitamin B Synthesis and Their Distribution in Microbial Producers

B vitamins (VBs) are essential micronutrients, yet their microbial production across natural habitats remains poorly understood. We analyzed 126,931 metagenome-assembled genomes to map the distribution of VB producers and constructed a database of 87 VB synthesis genes, identifying VB-independent producers and their environmental drivers. Soil and freshwater habitats harbored the greatest diversity of VB₁, VB₂, VB₇, VB₉, and VB₁₂ producers, whereas marine systems contained fewer. Biosynthetic capacity was rare for VB₅ and was limited for VB₃ and VB₆. Gammaproteobacteria are prolific producers, synthesizing up to eight VB types. Soil sulfur content and conductivity significantly enhanced VB production potential, linking beneficial microbes to improved soil health. We further validated VB₃ and VB₇ synthesis in Acinetobacter kookii, supporting our predictive framework. Because the identified producers include both beneficial and pathogenic taxa, careful evaluation is required. This work provides a robust gene database and a foundation for optimizing microbial VB production in agriculture and biotechnology.