The costs associated with extracellular enzyme production must ultimately be recovered from the substrates targeted by the enzymes. In other words, natural selection should force microbes to earn a “profit” from enzyme production. We are testing whether some substrates are simply too rare or dilute in the environment to be profitable targets for extracellular enzymes. Microbes may fail to evolve or express enzymes to degrade rare substrates, leading to slow turnover times for these compounds. We are using advanced mass-spectrometry approaches to characterize the structures and abundances of potential enzyme substrates. In the laboratory, we are using microcosms to determine how substrate concentration affects extracellular enzyme expression and evolution.
Funded by NSF Advancing Theory in Biology