Potential bacterial isolation by dosing metabolites in cross-feedings

Metabolic cross-feeding, in which species use metabolites of other members to promote their own growth, is vital for bacterial growth and survival. Thus, whether the unculturable bacteria can be isolated or purified from consortia by adding these essential metabolites remains elusive. In this study, mass spectrometry imaging vividly pictured symbionts supplied folate and gluconate to anammox bacteria to support their growth. After dosing folate and gluconate, the relative abundance and activity of anammox bacteria were substantially improved. Such enhancement is originated from the added folate and gluconate significantly eased metabolic burden of anammox bacteria as they no longer secreted the extracellular public goods to others for "resource exchange" during cross-feedings. On the other hand, the decreased supplement of extracellular "public goods" lead to the decay of symbionts with high demand for these metabolites in the consortia. This also deservedly increased the relative abundance of anammox bacteria. This study provides a new dimension to isolate specific functional bacteria based on metabolic cross-feedings.