In the age of connectomics, it is increasingly important to understand how the nodes and edges of a brain's anatomical network, or "connectome," gives rise to neural signaling and neural function. I will present the first comprehensive brain-wide cell-resolved causal measurements of how neurons signal to one another in response to stimulation in the nematode C. elegans. I will compare this signal propagation atlas to the worm's known connectome to address fundamental questions of structure and function in the brain.

Animals modify their behavioral outputs in response to changes in external and internal environments. We use the nematode, C. elegans to probe the pathways linking changes in internal states like hunger with behavior. We find that acute food deprivation alters the localization of two transcription factors, likely releasing an insulin-like peptide from the intestine, which in turn modifies chemosensory neurons and alters behavior. These results present a model for how inter-tissue signals to generate flexible behaviors via gut-brain signaling.

In this talk I will discuss our recent findings that sensory signals from the brain adjust the physiology and behavior of the nematode C. elegans, enabling this animal to deal with the lethal threat of hydrogen peroxide. Hydrogen peroxide (H2O2) is the most common chemical threat in the microbial battlefield. Prevention and repair of the damage that hydrogen peroxide inflicts on macromolecules are critical for health and survival. In the first part of the talk, I will discuss our findings that C. elegans represses their own H2O2 defenses in response to sensory perception of Escherichia coli, the nematode’s food source, because E. coli can deplete H2O2 from the local environment and thereby protect the nematodes. Thus, the E. coli self-defense mechanisms create a public good, an environment safe from the threat of H2O2, that benefits C. elegans. In the second part of the talk, I will discuss how the modulation of C. elegans’ sensory perception by the interplay of hydrogen peroxide and bacteria adjusts the nematode’s behavior to improve the nematode’s chances of finding a niche that provides both food and protection from hydrogen peroxide.

Microbes have shaped the evolution of eukaryotes and contribute significantly to the physiology and behavior of animals. Some of these traits are inherited by the progenies. Despite the vast importance of microbe-host communication, we still do not know how bacteria change short term traits or long-term decisions in individuals or communities. In this seminar I will present our work on how commensal and pathogenic bacteria impact specific neuronal phenotypes and decision making. The traits we specifically study are the degeneration and regeneration of neurons and survival behaviors in animals. We use the nematode Caenorhabditis elegans and its dietary bacteria as model organisms. Both nematode and bacteria are genetically tractable, simplifying the detection of specific molecules and their effect on measurable characteristics. To identify these molecules we analyze their genomes, transcriptomes and metabolomes, followed by functional in vivo validation. We found that specific bacterial RNAs and bacterially produced neurotransmitters are key to trigger a survival behavioral and neuronal protection respectively. While RNAs cause responses that lasts for many generations we are still investigating whether bacterial metabolites are capable of inducing long lasting phenotypic changes.

Traumatic injury in the nervous system leads to devastating consequences such as paralysis. The regenerative capacity of the nervous system is limited in adulthood. In this talk, Dr. Anindya would be sharing how the simple nematode C. elegans with its known connectome can inform us about the biology of nervous system repair.