CeMM-WormTracker: long-term, single-worm level tracking and phenotyping of <i>C. elegans</i> cultivated in CeMM on an integrated and enclosed microfluidic device

<i>Caenorhabditis elegans</i> (<i>C. elegans</i>) is a typical model organism that has predominantly relied on growth using a bacterial diet, presenting limitations for automated experimentations (mainly due to the requirement of periodic transfer to new plates), and accuracy of results (because of possible interference by bacterial metabolism in liquid media), which makes flexible manipulation and long-term tracking difficult. <i>C. elegans</i> Maintenance Medium (CeMM), a chemically defined sterile liquid medium, holds the potential to solve these problems. Population-level studies of <i>C. elegans</i> cultured in CeMM have shown that nematode development slows, fecundity declines, lifespan increases, lipid and protein stores decrease, and gene expression changes relative to that on a bacterial diet. However, automated cultivation of <i>C. elegans</i> in CeMM, long-term tracking and phenotyping at single-worm level remains challenging. Here, we developed a chamber-array chip (WormChip-1.8) and an integrated and enclosed microfluidic device, CeMM-WormTracker, with the capability of automating fluid control and worm manipulation for single-worm level tracking and phenotyping of <i>C. elegans</i> grown in CeMM. By using a microscope, the CeMM-WormTracker allows for observation of <i>C. elegans</i> development, motility, reproduction, and survival for a long period of time. Our data demonstrate that it is possible to longitudinally track and phenotype the growth and development of nematodes at single-worm level for at least 75 days within the device, enabling comprehensive monitoring of the whole reproductive period and lifespan in sterile liquid culture, which is difficult for well plate-based experiments. Comparing with the results from 96-well plates, the development, activity, and reproduction of nematodes in the microfluidic device seems more stable. Thus, the CeMM-WormTracker provides feasible solutions for automated and high-throughput experimentations in studies of <i>C. elegans</i>, both on the ground and in orbit.