Neuronal basis and diverse mechanisms of pathogen avoidance in Caenorhabditis elegans

Abstract

Pathogen avoidance behaviour has been observed across animal taxa as a vital host-microbe interaction mechanism. The nematode Caenorhabditis elegans has evolved multiple diverse mechanisms for pathogen avoidance under natural selection pressure. We summarise the current knowledge of the stimuli that trigger pathogen avoidance, including alterations in aerotaxis, intestinal bloating, and metabolites. We then survey the neural circuits involved in pathogen avoidance, transgenerational epigenetic inheritance of pathogen avoidance, signalling crosstalk between pathogen avoidance and innate immunity, and C. elegans avoidance of non-Pseudomonas bacteria. In this review, we highlight the latest advances in understanding host-microbe interactions and the gut-brain axis.

Keywords: aerotaxis; innate immunity; metabolites; neural circuit; pathogen avoidance; reactive oxygen species.

Figure 1

Mechanisms of pathogen avoidance. A variety of comprehensive mechanisms are in place to regulate pathogens avoidance, which include those caused by the alteration of aerotaxis, intestinal bloating, metabolites, transgenerational epigenetic inheritance, and crosstalk with innate immunity.

Figure 2

Essential neuronal basis of pathogen avoidance. (A) Several neural circuits contribute to the intricate process of pathogen avoidance. In essence, these circuits form a three-layer structure composed of ciliated sensory neurons, interneurons, and motor neurons. The sensory neurons play distinct roles: some are tasked with naïve preference, others with learned avoidance, and a select few handle both. (B) The regulation of pathogen avoidance is a collaborative effort between neurotransmitters and neuromodulators. Working in unison, they meticulously calibrate the process of pathogen avoidance.