Prevalent reliance of bacterioplankton on exogenous vitamin B1 and precursor availability

Significance Virtually all organisms require vitamin B1, including bacterioplankton that impact nutrient cycling and productivity in aquatic systems and Earth’s climate. Here, we show that B1 auxotrophy, the need for exogenous B1 or precursors for survival, is widespread among wild bacterioplankton. Genetic analyses of wild bacterioplankton revealed that most are B1 auxotrophs and the abundance of several B1-related genotypes changes temporally at an estuarine monitoring station, suggesting that B1/precursor availability influences bacterioplankton succession. Complementarily, in-field nutrient-amendment experiments and bioassays indicate that B1/precursor bioavailability periodically limits bulk growth of bacterioplankton. Together the presented data highlight the prevalent reliance of bacterioplankton upon exogenous B1/precursors and suggest a hitherto overlooked influence of B1/precursor availability on aquatic biochemical cycling.