Harnessing Microbial Tools: Escherichia coli as a Vehicle for Neuropeptide Functional Analysis in Caenorhabditis elegans.

Animals respond to changes in their environment and internal states via neuromodulation. Neuropeptides modulate neural circuits with flexibility because one gene can produce either multiple copies of the same neuropeptide or different neuropeptides. However, with this architectural complexity, the function of discrete and active neuropeptides is muddled. Here, we design a genetic tool that facilitates functional analysis of individual peptides. We engineered Escherichia  coli bacteria to express active peptides, fed loss-of-function Caenorhabditis elegans, and rescued the activity of genes with varying lengths and functions: pdf-1, flp-3, ins-6, and ins-22. Some peptides were functionally redundant, while others exhibit unique and previously uncharacterized functions. We postulate our rescue-by-feeding approach can elucidate the functional landscape of neuropeptides, identifying the circuits and complex peptidergic pathways that regulate different behavioral and physiological processes.