Different methods of killing bacteria diets differentially influence Caenorhabditis elegans physiology

Across species, diet plays a critical role in most, if not all life history traits. Caenorhabditis elegans is an important and facile organism for research across modalities, but the use of live bacteria as sources of nutrition can exert pleiotropic outcomes that stem from the action of host-pathogen defenses. Recently, a powerful new approach to readily generate dead and metabolically inactive Escherichia coli was developed that enabled reproducible measures of health across the lifespan. Here we further characterize additional comparisons of developmental and physiological parameters of animals fed either bacteria killed by treatment with ultraviolet (UV) light and bactericidal antibiotics or low-dose paraformaldehyde (PFA). Unlike bacteria killed by UV/Antibiotic treatment, PFA-killed diets resulted in a 25% reduction in body size just prior to adulthood and an overall reduction in stored intracellular lipids. Moreover, a small but reproducible number of animals fed PFA-killed bacteria display age-dependent depletion of somatic lipids, which does not normally occur on live bacteria or bacteria killed by UV/antibiotics. Lastly, animals fed PFA-treated, but not UV-antibiotic treated bacteria display a 10% increase in crawling speed. Taken together, these new data more thoroughly define the physiological impact two methodologies to prepare C. elegans diets that should be considered during experimental design.