Bite size of regulates feeding, satiety and development on a diet of live yeast.

In the wild, the nematode primarily feeds on microbes, which are abundant in rotting vegetation. Studies show that several gram-positive and gram-negative bacterial populations predominantly constitute the gut microbiome, but surprisingly lack any yeast species. To understand the lack of yeast in the intestine of , we studied the behaviour of worms on pathogenic and non-pathogenic yeast diets. We show that displays low satiety on a yeast diet of , or . We find that the average size of cells of budding yeast is much larger than that of , which constitute the laboratory diet of . We have shown that yeast cells cause pharyngeal obstruction, diminished feeding, and lower level of neutral lipids in adult . Using scanning electron microscopy, we show that the mouth size of larvae is smaller than the average yeast cell. The larvae have no detectable yeast in their alimentary canal, and they undergo delayed development on a yeast diet. We propose that microbial cell size or bite size could be crucial factors in the regulation of feeding in , and the composition of the microbiome in its intestine.