“Mitochondria are the powerhouses of the cell.” Repeated incessantly in high school biology textbooks, this slogan reminds students that these organelles, found in the cells of humans, plants, fungi and myriad other organisms, fuel vast swaths of biology, making use of abundant oxygen.
But researchers in this week’s Proceedings of the National Academy of Science report that a tiny parasitic cousin of jellyfish, which under a microscope looks something like the head of an archetypal bigheaded and dark-eyed alien, is bucking the trend: It has no mitochondria, suggesting it does not use oxygen for respiration. It appears to get its energy from some other source that remains mysterious.
Mitochondria, which are likely remnants of bacteria that took up residence in larger cells, have their own small genomes, separate from the genetic warehouse of the organism they are a part of. The researchers were hoping to compare the mitochondrial genomes in two species of these parasites, said Dorothée Huchon, a molecular geneticist at Tel Aviv University and an author of the new study. But when they looked at their data, they saw no sign of one in Henneguya salminicola, a parasite that lives inside the muscles of salmon and other fish.
“OK, something went wrong,” Dr. Huchon said she thought.
Running the analysis again brought the same results. Some of the genes in the organism’s genome that normally aid the mitochondria were also suspiciously missing or damaged. Further tests confirmed it — there was no mitochondrial genome at all, and hence no chance of the organism functioning the way researchers had expected, although there did seem to be a loose sac that might once have been the organelle.
This is not the first time researchers have found creatures that have ditched their mitochondria. Giardia, a parasite that causes gut troubles in people, and Trichomonas vaginalis, a parasite that drives the sexually transmitted infection trichomoniasis, have just a vestige of the original organelle, a sac that does not perform the traditional energy-producing role. It does do other things for the parasites — mitochondria have lesser-known jobs involving metabolism, for instance — but energy production is shifted to another set of enzymes.
What H. salminicola might be using instead to power itself is not clear, however, Dr. Huchon said. It does not have the same setup as Giardia and T. vaginalis. But the researchers think that the absence of a functioning mitochondrion might be linked to the peculiar environment where the parasite lives — fish muscle.
Mitochondria rely on the presence of oxygen to generate energy, and when there is no oxygen around, evolution might lead an organism to develop other ways of fueling itself. Other mitochondria-less organisms live in oxygen-poor environments, Dr. Huchon said.
“Our hypothesis is that this parasite is also in an oxygen-poor environment,” she said. “It’s in the muscle — it’s known that fish muscle is extremely poor in oxygen.”
But if it is anything like closely related parasites, it probably also spends part of its life cycle in a still-elusive worm species. The researchers are hoping to pinpoint which worm this might be. They are also curious whether the parasite might be siphoning some of its energy from its host, and whether it will still behave normally when deprived of oxygen in the lab.
The missing mitochondrial genome has opened up many questions for the group, Dr. Huchon said. It’s a reminder that though we tend to think of creatures gaining new functions rather than abandoning old ones, that is far from the reality.
“Evolution can go in strange directions,” she said.
2020-02-28 10:00:00Z
https://news.google.com/__i/rss/rd/articles/CBMiTGh0dHBzOi8vd3d3Lm55dGltZXMuY29tLzIwMjAvMDIvMjgvc2NpZW5jZS9wYXJhc2l0ZS1veHlnZW4tbWl0b2Nob25kcmlhLmh0bWzSAVBodHRwczovL3d3dy5ueXRpbWVzLmNvbS8yMDIwLzAyLzI4L3NjaWVuY2UvcGFyYXNpdGUtb3h5Z2VuLW1pdG9jaG9uZHJpYS5hbXAuaHRtbA?oc=5
Read Next >>>>
Bagikan Berita Ini
0 Response to "This Parasite Doesn’t Need Oxygen to Survive - The New York Times"
Post a Comment