Formate is an attractive one-carbon (C1) feedstock for biomanufacturing due to its low cost, high solubility, and compatibility with electricity-driven CO₂ reduction. However, natural assimilation of formate is limited to a few bacterial species. I will discuss the engineering of the soil bacterium Pseudomonas putida to assimilate formate as its sole carbon and energy source via the linear reductive glycine pathway. Through a combination of rational design and adaptive laboratory evolution (ALE), initial strains were optimized for mixotrophic growth, leading to mutations in promoter regions of synthetic genes and the native genome that facilitated metabolic integration. Strict formatotrophy was established by introducing a formate dehydrogenase gene and applying growth-coupled selection. Building on this platform, microbial growth was linked to the biosynthesis of complex metabolites. As an example, a formatotrophic P. putida strain was engineered to couple xanthommatin production—a color-shifting animal pigment—with growth by creating a 5,10-methylenetetrahydrofolate auxotrophy dependent on endogenous formate levels. This modular system was further refined through ALE, enabling efficient, gram-scale pigment biosynthesis. These findings establish P. putida as the first strictly formatotrophic member of its genus and highlight its potential as a robust host for scalable, growth-coupled production of high-value compounds from C1 substrates.