The nematode Caenorhabditis elegans is one of the premier experimental model organisms today. In the laboratory, they display characteristic development, fertility, and behaviors in a two dimensional habitat. In nature, however, C. elegans is found in three dimensional environments such as rotting fruit. To investigate the biology of C. elegans in a 3D controlled environment we designed a nematode cultivation habitat which we term the nematode growth tube or NGT-3D. NGT-3D allows for the growth of both nematodes and the bacteria they consume. Worms show comparable rates of growth, reproduction and lifespan when bacterial colonies in the 3D matrix are abundant. However, when bacteria are sparse, growth and brood size fail to reach levels observed in standard 2D plates. Using NGT-3D we observe drastic deficits in fertility in a sensory mutant in 3D compared to 2D, and this defect was likely due to an inability to locate bacteria. Overall, NGT-3D will sharpen our understanding of nematode biology and allow scientists to investigate questions of nematode ecology and evolutionary fitness in the laboratory.

As space flight becomes more accessible in the future, humans will be exposed to gravity conditions other than our 1G environment on Earth. Our bodies and physiology, however, are adapted for life at 1G gravity. Altering gravity can have profound effects on the body, particularly the development of muscles, but the reasons and biology behind gravity’s effect are not fully known. We asked whether increasing gravity had effects on the development of motor neurons that innervate and control muscle, a relatively unexplored area of gravity biology. Using the nematode model organism Caenorhabditis elegans, we examined changes in response to hypergravity in the development of the 19 GABAergic DD/VD motor neurons that innervate body muscle. We found that a high gravity force above 10G significantly increases the number of animals with defects in the development of axonal projections from the DD/VD neurons. We showed that a critical period of hypergravity exposure during the embryonic/early larval stage was sufficient to induce defects. While characterizing the nature of the axonal defects, we found that in normal 1G gravity conditions, DD/VD axonal defects occasionally occurred, with the majority of defects occurring on the dorsal side of the animal and in the mid-body region, and a significantly higher rate of error in the 13 VD axons than the 6 DD axons. Hypergravity exposure increased the rate of DD/VD axonal defects, but did not change the distribution or the characteristics of the defects. Our study demonstrates that altering gravity can impact motor neuron development.

The growing enthusiasm for cancer immunotherapies and adoptive cell therapies has prompted increasing interest in biomaterials development mimicking natural antigen‐presenting cells (APCs) for T‐cell expansion. In contrast to conventional bottom‐up approaches aimed at layering synthetic substrates with T‐cell activation cues, transformation of live dendritic cells (DCs) into artificial APCs (aAPCs) is demonstrated herein using a facile and minimally disruptive hydrogelation technique. Through direct intracellular permeation of poly(ethylene glycol) diacrylate (PEG‐DA) hydrogel monomer and UV‐activated radical polymerization, intracellular hydrogelation is rapidly accomplished on DCs with minimal influence on cellular morphology and surface antigen display, yielding highly robust and modular cell–gel hybrid constructs amenable to peptide antigen exchange, storable by freezing and lyophilization, and functionalizable with cytokine‐releasing carriers for T‐cell modulation. The DC‐derived aAPCs are shown to induce prolonged T‐cell expansion and improve anticancer efficacy of adoptive T‐cell therapy in mice compared to nonexpanded control T cells, and the gelation technique is further demonstrated to stabilize primary DCs derived from human donors. The work presents a versatile approach for generating a new class of cell‐mimicking biomaterials and opens new venues for immunological interrogation and immunoengineering.

Animals sense an enormous number of cues in their environments, and, over time, can form learned associations and memories with some of these. The nervous system remarkably maintains the specificity of learning and memory to each of the cues. Here we asked whether the nematode Caenorhabditis elegans adjusts the temporal dynamics of adaptation and aversive learning depending on the specific odor sensed. C. elegans senses a multitude of odors, and adaptation and learned associations to many of these odors requires activity of the cGMP-dependent protein kinase EGL-4 in the AWC sensory neuron. We identified a panel of 17 attractive odors, some of which have not been tested before, and determined that the majority of these odors require the AWC primary sensory neuron for sensation. We then devised a novel assay to assess odor behavior over time for a single population of animals. We used this assay to evaluate the temporal dynamics of adaptation and aversive learning to 13 odors and find that behavior change occurs early in some odors and later in others. We then examined EGL-4 localization in early-trending and late-trending odors over time. We found that the timing of these behavior changes correlated with the timing of nuclear accumulation of EGL-4 in the AWC neuron suggesting that temporal changes in behavior may be mediated by aversive learning mechanisms. We demonstrate that temporal dynamics of adaptation and aversive learning in C. elegans can be used as a model to study the timing of memory formation to different sensory cues.

Maternal behaviors benefit the survival of young, contributing directly to the mother's reproductive fitness. An extreme form of this is seen in matriphagy, when a mother performs the ultimate sacrifice and offers her body as a meal for her young. Whether matriphagy offers only a single energy-rich meal or another possible benefit to the young is unknown. Here, we characterized the toxicity of a bacterial secondary metabolite, namely, violacein, in Caenorhabditis elegans and found it is not only toxic towards adults, but also arrests growth and development of C. elegans larvae. To counteract this, C. elegans resorted to matriphagy, with the mothers holding their eggs within their bodies and hatching the young larvae internally, which eventually led to the mothers' death. This violacein-induced matriphagy alleviated some of the toxic effects of violacein, allowing a portion of the internally-hatched young to bypass developmental arrest. Using genetic and pharmacological experiments, we found the consumption of oleate, a monounsaturated fatty acid produced by the mother, during matriphagy is partially responsible. As such, our study provides experimental evidence of why such a drastic and peculiar maternal behavior may have arisen in nematode natural habitats. Animals go to extraordinary lengths to increase the survival and reproductive fitness of their young. Matriphagy, which occurs when organisms consume their own mother, is an extreme adaptation that is observed in some animals. For instance, in the spider species Diaea ergandros and Amaurobius ferox, mothers willingly and, in the case of A. ferox, actively invite their young to devour them 1. Although matriphagy eliminates the mother's ability to provide for and protect their brood, or even reproduce again, the nutritional benefit to the young outweighs these deficiencies 1. Predators of bacteria are a major factor controlling the death and survival of bacteria in their native environments 7. In response, microbes have evolved diverse methods to combat predation, including the synthesis of toxic secondary metabolites 8. One such compound that decreases the survival of microbial predators is violacein 9,10. Violacein is a bis-indole secondary metabolite produced in a diverse array of bacteria 2 , where its production is regulated by quorum-sensing mechanisms 3,4. Violacein is toxic to many organisms including Gram-positive bacteria 4 , fungi 5 , and protozoa 6,7. Violacein production, which is an energy expensive process due to being a derivative of two tryptophan molecules 8 , is considered an adapted defense mechanism to protozoal grazing of bacteria 9. Animals are not free from the effects of violacein either: the free-living hermaphroditic nematode Caenorhabditis elegans is also susceptible to violacein toxicity. C. elegans feeding on a strain of E. coli engineered to produce violacein had decreased survival 10 , and learned to avoid violacein-producing E. coli 11 .