Small Molecule Extracellular Electron Shuttles: A Link between Primary and Secondary Metabolism

Microbial natural products exhibit a wide range of ecological functions including antibacterial, iron scavenging, and quorum sensing capabilities. However, these molecules can also play tangential roles in primary metabolism. Bacterial respiration occurs in many different forms, often subject to the availability of terminal electron acceptors such as oxygen. However, when terminal electron acceptors become scarce, the electron transport chain locks up and energy production stops. Interestingly, some bacteria have evolved methods of extending their central metabolism outside of the cell in order to access distant terminal electron acceptors, stabilizing their electron transport chain. One observed method of extracellular electron transport involves the secretion of redox active small molecule electron shuttles, which are capable of extracellularly extending the cells redox capabilities. These natural products play a crucial physiological role that allows aerobic bacteria to survive in oxygen limited environments. This thesis explores our current understanding of this relatively underexplored function of small molecule natural products, with a focus on how they may play a role in marine sediments. Moreover, information on their environmental distribution, biosynthesis, phylogeny, physiological roles, and biotechnological applications is also provided