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Biologists Discover Animal that Lacks Mitochondrial Genome, Doesn't Need Oxygen to Live | Biology – Sci-News.com

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An international team of biologists has discovered that a tiny parasite of salmon called Henneguya salminicola has no mitochondrial genome and thus has lost the ability to perform aerobic respiration.

Henneguya salminicola, also known as Henneguya zschokkei, has large nuclei but surprisingly no mitochondrial nucleosomes. Image credit: Yahalomi et al, doi: 10.1073/pnas.1909907117.

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Although aerobic respiration is a hallmark of eukaryotes, a few unicellular lineages, growing in hypoxic environments, have secondarily lost this ability.

In the absence of oxygen, the mitochondria of these organisms have lost all or parts of their genomes and evolved into mitochondria-related organelles.

“Aerobic respiration was thought to be ubiquitous in animals, but now we confirmed that this is not the case,” said team leader Professor Dorothee Huchon, a researcher in the School of Zoology at Tel Aviv University and the Steinhardt Museum of Natural History.

“Our discovery shows that evolution can go in strange directions. Aerobic respiration is a major source of energy, and yet we found an animal that gave up this critical pathway.”

In the study, Professor Huchon and colleagues from the University of Kansas, Oregon State University and Tel Aviv University sequenced and analyzed the genome of Henneguya salminicola, a tiny, less than ten-celled parasite of salmonid fish.

The analyses suggest that the microscopic animal lost not only its mitochondrial genome but also nearly all nuclear genes involved in transcription and replication of the mitochondrial genome.

TEM image of Henneguya salminicola mitochondrion-related organelle (center) with few cristae. Image credit: Yahalomi et al, doi: 10.1073/pnas.1909907117.

TEM image of Henneguya salminicola mitochondrion-related organelle (center) with few cristae. Image credit: Yahalomi et al, doi: 10.1073/pnas.1909907117.

Until this discovery, there was debate regarding the possibility that organisms belonging to the animal kingdom could survive in anaerobic environments.

The assumption that all animals are breathing oxygen was based, among other things, on the fact that animals are multicellular, highly developed organisms, which first appeared on Earth when oxygen levels rose.

“It’s not yet clear to us how the parasite generates energy,” Professor Huchon said.

“It may be drawing it from the surrounding fish cells, or it may have a different type of respiration such as oxygen-free breathing, which typically characterizes anaerobic non-animal organisms.”

“The discovery bears enormous significance for evolutionary research,” she said.

“It is generally thought that during evolution, organisms become more and more complex, and that simple single-celled or few-celled organisms are the ancestors of complex organisms.”

“But here, right before us, is an animal whose evolutionary process is the opposite. Living in an oxygen-free environment, it has shed unnecessary genes responsible for aerobic respiration and become an even simpler organism.”

The discovery is reported in a paper in the Proceedings of the National Academy of Sciences.

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Dayana Yahalomi et al. A cnidarian parasite of salmon (Myxozoa: Henneguya) lacks a mitochondrial genome. PNAS, published online February 24, 2020; doi: 10.1073/pnas.1909907117

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New branch on tree of life includes ‘lions of the microbial world’

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There’s a new branch on the tree of life and it’s made up of predators that nibble their prey to death.

These microbial predators fall into two groups, one of which researchers have dubbed “nibblerids” because they, well, nibble chunks off their prey using tooth-like structures. The other group, nebulids, eat their prey whole. And both comprise a new ancient branch on the tree of life called “Provora,” according to a paper published today in Nature.

Microbial lions

Like lions, cheetahs, and more familiar predators, these microbes are numerically rare but important to the ecosystem, says senior author Dr. Patrick Keeling, professor in the UBC department of botany. “Imagine if you were an alien and sampled the Serengeti: you would get a lot of plants and maybe a gazelle, but no lions. But lions do matter, even if they are rare. These are lions of the microbial world.”

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Using water samples from marine habitats around the world, including the coral reefs of Curaçao, sediment from the Black and Red seas, and water from the northeast Pacific and Arctic oceans, the researchers discovered new microbes. “I noticed that in some water samples there were tiny organisms with two flagella, or tails, that convulsively spun in place or swam very quickly. Thus began my hunt for these microbes,” said first author Dr. Denis Tikhonenkov, senior researcher at the Institute for Biology of Inland Waters of the Russian Academy of Sciences.

Dr. Tikhonenkov, a long-time collaborator of the UBC co-authors, noticed that in samples where these microbes were present, almost all others disappeared after one to two days. They were being eaten. Dr. Tikhonenkov fed the voracious predators with pre-grown peaceful protozoa, cultivating the organisms in order to study their DNA.

“In the taxonomy of living organisms, we often use the gene ’18S rRNA’ to describe genetic difference. For example, humans differ from guinea pigs in this gene by only six nucleotides. We were surprised to find that these predatory microbes differ by 170 to 180 nucleotides in the 18S rRNA gene from every other living thing on Earth. It became clear that we had discovered something completely new and amazing,” Dr. Tikhonenkov said.

New branch of life

On the tree of life, the animal kingdom would be a twig growing from one of the boughs called “domains,” the highest category of life. But sitting under domains, and above kingdoms, are branches of creatures that biologists have taken to calling “supergroups.” About five to seven have been found, with the most recent in 2018 — until now.

Understanding more about these potentially undiscovered branches of life helps us understand the foundations of the living world and just how evolution works.

“Ignoring microbial ecosystems, like we often do, is like having a house that needs repair and just redecorating the kitchen, but ignoring the roof or the foundations,” said Dr. Keeling. “This is an ancient branch of the tree of life that is roughly as diverse as the animal and fungi kingdoms combined, and no one knew it was there.”

The researchers plan to sequence whole genomes of the organisms, as well as build 3D reconstructions of the cells, in order to learn about their molecular organization, structure and eating habits.

International culture

Culturing the microbial predators was no mean feat, since they require a mini-ecosystem with their food and their food’s food just to survive in the lab. A difficult process in itself, the cultures were initially grown in Canada and Russia, and both COVID and Russia’s war with Ukraine prevented Russian scientists from visiting the lab in Canada in recent years, slowing down the collaboration.

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How A Hellish Planet Made Of Diamonds Covered By A Lava Ocean Got Where It Is Today

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In recent decades it’s become clear that the universe is teeming with planets and astronomers have begun to catalog them by the hundreds. Most of the worlds we’ve discovered so far are remarkably inhospitable and the closer we look at some, the more hellacious they seem to appear.

Case in point is 55 Cancri e, also known as 55 Cnc or by its nickname, Janssen. This world orbits so close to its star, known as Copernicus or 55 Cnc, that a year on its surface passes in only 18 hours and temperatures can soar over 4,000 degrees Fahrenheit.

Enduring such extreme conditions for so long has led scientists to suggest that the scalding world could have an interior full of diamonds, covered by a surface ocean of molten lava.

Makes Mauna Loa seem almost minor league on the cosmic scale of volcanism.

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There’s a reason that we keep spotting so many relatively hot planets next to their stars. Call it an inherent bias of our existing tech: it’s just easier to see planets orbiting close in to their stars.

In fact, most exoplanets discovered and cataloged so far have a very good chance of being so-called “hot Jupiters” — giant planets orbiting close-in. Being massive and next to your local source of light makes you especially easy to spot.

So 55 Cancri e is actually an important exoplanet as one of the first small, rocky planets found orbiting extremely close to its star.

Now researchers have made use of a new tool called EXPRES (for EXtreme PREcision Spectrometer) at the Lowell Discovery Telescope in Arizona to make ultra-precise measurements that helped them determine the orbit of this hellish world in more detail.

They found that the planet orbits Copernicus right along the equator of the star and that it likely originally orbited further out and was slowly pulled into its current alignment by the gravitational pull of the star and other objects in the unusual star system.

The system is located only 40 light years from Earth and consists of main-sequence star Copernicus paired with a red dwarf star. The binary duo also count at least five exoplanets that all have very different orbits among their cosmic family.

The new research, led by Lily Zhao at Flatiron Institute’s Center for Computational Astrophysics and published in Nature Astronomy, posits that the interactions between these oddball family members shifted Janssen to its current, insufferable orbit.

Although it was pushed, pulled and prodded into its current position, Zhao says that even in its original orbit, the planet “was likely so hot that nothing we’re aware of would be able to survive on the surface.”

What a waste of so much diamond.

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Rare Mars eclipse by the full moon wows stargazers with occultation

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On Wednesday (Dec. 7), skywatchers around the world were treated to a celestial show as the full moon eclipsed Mars in the night sky.

The rare event, known as a lunar occultation, refers to one celestial body — in this case, Mars — appearing to disappear or hide behind another — in this case, the moon. This occultation was particularly noteworthy because Mars was at opposition, meaning Earth was directly between it and the sun, making the Red Planet appear particularly bright in the night sky.

Last night’s occultation of Mars by the full moon produced some gorgeous images from observers around the world. The Griffith Observatory in California had a great view of the moon and Mars joining up on Dec. 7 and caught a time-lapse of the Red Planet disappearing behind Earth’s celestial companion as seen in the video above.

In addition, skywatchers around the world have been posting gorgeous images of the lunar occultation of Mars on social media, offering a look at one of the year’s most-watched celestial events.

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Astrophotographer Andrew McCarthy caught Mars and the full moon (opens in new tab) in a beautiful close-up:

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Spaceflight photographer John Kraus caught a stunning shot of Mars (opens in new tab) as it appeared behind the moon following occultation:

Amateur astrophotographer Tom Williams produced a gorgeous image of the moon and Mars by combining multiple photographs, and offered an explanation of how he made the image (opens in new tab) on Twitter.

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Amateur astronomer and photographer Tom Glenn produced a breathtaking image of Mars (opens in new tab) rising above the moon by stacking 15 different photograph frames.

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Astronomer and science communicator Phil Plait caught Mars creeping behind the moon (opens in new tab) just prior to occultation.

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The lunar occultation of Mars by the full Cold Moon was particularly noteworthy because the Red Planet only appears at opposition every 26 months, so the next opposition won’t occur until January 2025.

Mars was also especially close to Earth during this event, which occurred while the planet was at perigee, or its closest point to Earth in its orbit. The record for closest approach between Mars and Earth was set in 2003 at just 34.8 million miles (56 million kilometers); according to NASA, Mars and Earth won’t be this close for another 265 years, until 2287.

Editor’s Note: If you snap a great photo of either Mars at opposition or the lunar occultation and would like to share it with Space.com’s readers, send your photo(s), comments, and your name and location to spacephotos@space.com

Editor’s Note: This piece was updated at 4:30 p.m. EST (2130 GMT) on Dec. 8 to indicate that the record for Mars’ closest approach to Earth was set in 2003.

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