Bite size ofCaenorhabditis elegansregulates feeding, satiety and development on yeast diet
ABSTRACTIn the wild, the soil dwellingnematode Caenorhabditis elegansprimarily feeds on microbes which are abundant in rotting vegetation. Recent published studies showthat several Gram-positive and Gram-negative bacterial populations predominantly constitutes theC. elegansgut microbiome but surprisingly lack any yeast species. Here, we show thatC. elegansdisplay low satiety on yeast diet ofCryptococcus neoformans, C. laurentiiorS. cerevisiae. We found that average size of budding yeast cells is much larger thanE. colicells. Yeast cells also cause pharyngeal obstruction, diminished feeding, and lower level of neutral lipids in adultC. elegans. Using scanning electron microscopy, we show that the mouth size ofC. eleganslarvae is smaller than average yeast cell. The larvae have no detectable yeast in their alimentary canal and they undergo delayed development on yeast diet. We propose that microbial cell size or bite size could be one of the crucial factors in regulation of feeding inC. elegans.IMPORTANCEThe microbiome inC. elegansgut is composed of diverse genera of bacteria but it lacks yeast and other fungi. In this study, we provide evidence that yeast cell size is bigger than the mouth size ofC. eleganslarvae. We propose that “bigger than the bite’’ size of yeast cells is one possible reason for low satiety on yeast diet, reduced feeding, lower stored lipids and delayed development. The bite size threshold imposed byC. elegansmouth can, partly, explain absence of yeast inC. elegansnative gut microbiome and “bite size’’ can be studied further as a determinant of microbiome diversity in other animals.