“…However, sampling intracellular metabolites without either changing their relative concentrations or introducing contamination from supernatant metabolites is not straightforward, and research methods are still under active development by different groups (7,12,15,59,62). In contrast, exometabolome or supernatant profiling ("metabolic footprinting") is simple, and extracellular metabolites can exhibit very large changes in pool size (1,27,40,45). These multiple advantages mean that exometabolome analysis has already been used for a number of diverse applications, such as phenotyping of both single-gene deletion mutants and isolates from natural populations, although thus far mostly for fungi rather than bacteria (1,2,9,25,40,48).…”