Nematodes: The most abundant organism on Earth
N-NOSE is a cancer screening system that takes advantage of the characteristics of nematodes.
Nematode, or roundworm, is the common name for animals constituting the phylum Nematoda, which inhabit environments ranging broadly from soil to marine water to within other organisms.
Of all organisms living on Earth, nematodes are believed to have the largest species count. Some estimates say as many as 100 million nematodes exist, far outnumbering the estimated 5–10 million insects.
(N-NOSE uses the species of nematode called C. elegans.)
Characteristics of C. elegans
- Transparent, about 1 mm in length
- Has a brain and nervous, digestive, and reproductive systems
- Grown inexpensively on the coliform bacterium E. coli
- Hermaphrodite that readily generates genetically identical progeny
- All cells of a live specimen can be observed with a microscope
What are nematodes?
Takayuki Uozumi, Research and Development Leader, Hirotsu Bio Science Inc.
At Hirotsu Bio Science Inc., we are conducting research into the cancer screening system N-NOSE, which takes advantage of the high olfactory sensitivity of a certain organism.
This organism is the nematode C. elegans.
Few may be familiar with this species.
Let’s take a look at its characteristics.
Nematodes, or roundworms, constitute a diverse animal phylum that includes Ascaris lumbricoides (giant roundworm) Bursaphelenchus xylophilus (pine wood nematode), and Heterodera glycines (soybean cyst nematode).
The nematode we use is a species called Caenorhabditis elegans, abbreviated as C. elegans, which is studied extensively as a model organism for understanding biological phenomena.
C. elegans is a transparent nematode about 1 millimeter in length. In nature, it lives in soil.
Because it has no eyes or ears, it relies on olfaction for navigating the environment and detecting food. C. elegans is known to have a well-developed sense of smell.
C. elegans is a hermaphrodite capable of self-fertilization.
That is, a single specimen can produce both egg cells and sperm cells for generating progeny.
Each worm lays as many as 300 eggs, making it easy to grow C. elegans populations.
Hatched eggs develop into adults through four larval stages, L1 through L4, each marked by a molt of cuticle.
The speed of growth from egg to adult is affected by temperature. At 16°C it takes about 8 days, and at 20°C about 3.5 days.
Owing to these characteristics, C. elegans is a popular model organism in biological research.
(Model organisms are selected as a subject of extensive research in the various fields of biology. With the infinite number of organisms that exist, biologist cannot possibly study them all. So they select a few as model organisms with an eye to elucidating universal phenomena.)
Thanks to characteristics such as readiness to breed and grow, and ease of observation despite being a multicellular organism, C. elegans has been the subject of a great many studies.
And as a result of these studies, C. elegans is the first organism to have its whole genome sequenced as well as be the subject of three Nobel Prize-winning projects.