Anin vivomicrofluidic study of bacterial transit inC. elegansnematodes

Caenorhabditis elegans(C. elegans) constitutes an important model organism for use in nutrition and aging studies. We report a novel method for studying the dynamics ofEscherichia coli(E. coli) bacterial transit through the worms' intestine. A microfluidic chip was designed for alternatingC. eleganson-chip culture and immobilization, thereby enabling periodic high-resolution time-lapse imaging at single-worm resolution over several days. Immobilization was achieved in a reversible way using arrays of tapered channels suitable for assay parallelization. DedicatedC. elegansfeeding protocols were applied. TwoE. colibacterial strains, HT115 and OP50, respectively labeled with green fluorescent protein (GFP) and red fluorescent protein (RFP), were used as food source and imaged with fluorescence microscopy techniques to measure relevant parameters of the bacterial transit process. Feeding behavior andE. colitransit dynamics in the whole intestinal tract of the worms were characterized in an automated way over the first 3 days of adulthood, revealing both fast transit phenomena and variations in microbial accumulation. In particular, we studied the bacterial food transit periodicity in wild-type andeat-2(ad465) mutantC. elegansstrains in both trapped and free-swimming conditions. In order to further demonstrate the versatility of our microfluidic platform, we also studied drug-induced modifications of the bacterial transit by measuring the response of the worms' intestine to exposure to the neurotransmitter serotonin