Caenorhabditis elegans is one of the most commonly used model organisms in biology and genetic research. Its transparent body and simple life history readouts make it an ideal tool for studying interactions with the microbiome. The worm has an elongated cylindrical body tapered at both ends, no segmentation, smooth skin, and no appendages. Adults grow to approximately 1mm in length and contain 959 somatic cells.

The nematode's body and nervous system are highly similar to those of mammals, and it also contains about 65% of human disease genes. It is also easy to manipulate and has an efficient, rapid, and reliable life cycle. This is important for research on many diseases including those that have a short or non-sudden mortality, such as Parkinson's disease.

In contrast, the mammalian model elicits a complex and often unpredictable response to environmental stressors. This is due in part to the high level of mutations that occur during development. Moreover, mammalian animals do not exhibit the same kind of complex behavior and body structure as C. elegans (Edgley, 1999; Corsi & Wightman, 2015).

Despite these differences, there is considerable overlap in the nematode's body structure, nervous system, and behavioral readouts with mammals. This has resulted in many advances in the field of nematode-inspired science, including: artificial intelligence, machine learning, and computational techniques (Edgley, 1999; Corsi, Wightman, Chalfie & Shapira, 2015; Greer et al., 2017).

Nematode in vivo Probiota longevity science research

The probiota of the nematode C. elegans includes a broad range of bacterial phyla that are common across natural, lab-enriched, and microcosm substrates. These bacterial families are known to support various processes in the worm, such as nutrient cycling, immunity, and metabolome optimization. In addition, some bacteria may provide a range of non-nutritional benefits to the host.

It is unknown, however, how the nematode acquires the different members of the characteristic gut microbiota. Although it has been shown that nematode-specific symbionts are acquired through natural environments and in a predictable manner, it is not clear why the host selects them and how they influence physiology. The acquisition of symbionts in a more diverse environment is likely mediated by mechanisms that permit partner choice or check for partner fidelity, but identifying the symbiotic bacterial taxa that are most beneficial to the worm remains elusive.

There are also a large number of non-symbiotic bacterial groups that have been found to support the worm in ways that are unrelated to nutrient regulation or immune function. Among these are bacteria that increase worm lifespan and reproduction, and reduce pathogen colonization in the intestines by increasing epithelial integrity. A recent study found that a non-pathogenic strain of the bacterium MYb11 slowed down the growth of enteropathogenic Escherichia coli by inhibiting intestinal cell death in the worm's digestive tract. Similarly, a non-pathogenic Pseudomonad has been shown to protect against nematode toxicity and reduce inflammation in the nematode's lungs (Dirksen et al., 2016).

Currently, it is unclear whether the worm's gut microbiota is derived from its environment or if it evolved in the absence of environmental microorganisms. Therefore, understanding the role of the nematode's gut microbiome in the worm's life history is an essential step towards elucidating the underlying mechanisms that govern its biology and contribute to its unique traits. Ultimately, this knowledge could help scientists understand the impact of different biotic and abiotic stresses on C. elegans, which in turn could lead to new and improved therapeutic approaches.

Author:

Kerry C.

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