fig2

Figure 2. Schematic overview of the key methodological approaches used to assess microbial vitamin biosynthesis, interspecies interactions, and physiological relevance in vivo. The diagram illustrates culture-independent methods (metagenomics, transcriptomics), culture-dependent strategies (isolation, genome sequencing, microbiological assays), and host-associated models (e.g., murine systems). Analytical chemistry and metabolomics methods can complement and be integrated across all these approaches to directly detect and quantify vitamin production and exchange.