MAY 13, 2016 06:24 AM PDT

Eukaryote Found That Lacks Mitochondria Powerhouse

WRITTEN BY: Carmen Leitch
Mitochondria have long been thought to be the normal engine of a eukaryotic cell and one that was essential for the survival of fungi, plants, animals and other organisms. Now, a single-cell microbe has been discovered that does not contain one. It was once thought that Giardia intestinalis, a microbe that causes diarrhea, was without a mitochondria but upon closer inspection, both it and other candidates were only false alarms and turned out to contain modified versions of the organelles. Mitochondria have undergone many changes over the course of evolution, with some becoming basically derivatives of one. The organelles themselves are the remnants of bacteria that integrated into primordial cells and eventually become the workhorse for their hosts.
The endosymbiotic origin of mitochondria
Researchers at Charles University in Prague have now investigated a new prospective candidate, a single-celled organism that lives in the intestines of a chinchilla, one that also happens to be a pet of a lab member. This microbe was selected because it is part of the genus Monocercomonoides, a group suggested to be lacking mitochondria.

First they sequenced the genome of the Monocercomonoides and saw that it did not contain any genes from mitochondrial DNA (mitochondria contain their own genome.) On further investigation, they were not able to detect any of the proteins that are critical for the function of the organelle. “The definition of eukaryotic cells is that they have mitochondria,” said Anna Karnkowska, the lead author of the study. “We overturn this definition.”
A Monocercomonoides cell
It’s possible that because of its typical environment, chinchilla guts, where oxygen is scarce and nutrients are abundant, it has no need for mitochondria. The researchers suggest that it harbors special cytoplasmic enzymes that allow it to metabolize food and generate energy. To fulfill other needs normally serviced by mitochondria, it has bacterial genes for those such as the synthesis of iron and sulfur clusters required for protein function.
How does a cell jettison a mitochondria?
Evolutionary genomicist B. Franz Lang of the University of Montreal in Canada commented, “It’s a very solid paper experimentally. If you’d like me to bet, I’d give them 90% probability that they are correct.” He would like to see the researchers strengthen their case by performing a very detailed microscopic analysis to confirm the absence of the organelles. Mark van der Giezen, an evolutionary biochemist of the University of Exeter in the United Kingdom, would also like to see further evidence that Monocercomonoides doesn’t contain rudimentary mitochondria. Regardless, he says, this study broadens our view of eukaryotes’ capabilities. “It shows that eukaryotic life is more flexible than what the textbooks say.” Monocercomonoides is not some ancient microbe hailing from times of the earliest eukaryotes, Karnkowska says. The closest relatives it has still contain small mitochondria, so it may have jettisoned the organelles in fairly recent evolutionary terms. She and her colleagues think that there are other mitochondria-free eukaryotes awaiting discovery. “This is one striking example, and I hope we can find others,” she says.

Sources: Science, Cell
About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
NOV 05, 2018
Neuroscience
NOV 05, 2018
Stress: Men Vs. Women
Undersatnding the gender specific differences in response to stress...
NOV 19, 2018
Cell & Molecular Biology
NOV 19, 2018
How Mitochondria can Help the Cell Fight Pathogens
Some pathogens can get around out bodies' natural defense mechanisms. So our body developed a Plan B....
NOV 20, 2018
Videos
NOV 20, 2018
A Major Grant Aims to Improve our Understanding of Age-related Cognitive Decline
The American Heart Association has teamed up with the Allen Initiative in Brain Health and Cognitive Impairment to award the Salk Institute $19.2 million....
NOV 19, 2018
Neuroscience
NOV 19, 2018
Thalamus plays a role in cognitive flexibility
Cognitive flexibility is our brain's ability to shift from thinking about one thing to another. The higher your speed of moving gears, the greater your cognitive flexibility....
DEC 05, 2018
Videos
DEC 05, 2018
Promising Results From Early Trials of Gene Therapy for Sickle Cell Anemia
More than 90,000 Americans and millions of people around the world have SCA....
DEC 08, 2018
Cardiology
DEC 08, 2018
Adaptations Of The Heart To Chronic Exercise
We have all heard that exercise is good for us, particularly for the heart, but many don’t understand precisely how regular, long-term activity affec...
Loading Comments...