Some truths about the Universe and our experience in it seem immutable. The sky is up. Gravity sucks. Nothing can travel faster than light. Multicellular life needs oxygen to live. Except we might need to rethink that last one.
Scientists have just discovered that a jellyfish-like parasite doesn’t have a mitochondrial genome – the first multicellular organism known to have this absence. That means it doesn’t breathe; in fact, it lives its life completely free of oxygen dependency.
This discovery isn’t just changing our understanding of how life can work here on Earth – it could also have implications for the search for extraterrestrial life.
Life started to develop the ability to metabolise oxygen – that is, respirate – sometime over 1.45 billion years ago. A larger archaeon engulfed a smaller bacterium, and somehow the bacterium’s new home was beneficial to both parties, and the two stayed together.
That symbiotic relationship resulted in the two organisms evolving together, and eventually those bacteria ensconced within became organelles called mitochondria. Every cell in your body except red blood cells has large numbers of mitochondria, and these are essential for the respiration process.
They break down oxygen to produce a molecule called adenosine triphosphate, which multicellular organisms use to power cellular processes.
We know there are adaptations that allow some organisms to thrive in low-oxygen, or hypoxic, conditions. Some single-celled organisms have evolved mitochondria-related organelles for anaerobic metabolism; but the possibility of exclusively anaerobic multicellular organisms has been the subject of some scientific debate.
That is, until a team of researchers led by Dayana Yahalomi of Tel Aviv University in Israel decided to take another look at a common salmon parasite called Henneguya salminicola.
It’s a cnidarian, belonging to the same phylum as corals, jellyfish and anemones. Although the cysts it creates in the fish’s flesh are unsightly, the parasites are not harmful, and will live with the salmon for its entire life cycle.
Tucked away inside its host, the tiny cnidarian can survive quite hypoxic conditions. But exactly how it does so is difficult to know without looking at the creature’s DNA – so that’s what the researchers did.
They used deep sequencing and fluorescence microscopy to conduct a close study of H. salminicola, and found that it has lost its mitochondrial genome. In addition, it’s also lost the capacity for aerobic respiration, and almost all of the nuclear genes involved in transcribing and replicating mitochondria.
Like the single-celled organisms, it had evolved mitochondria-related organelles, but these are unusual too – they have folds in the inner membrane not usually seen.
The same sequencing and microscopic methods in a closely related cnidarian fish parasite, Myxobolus squamalis, was used as a control, and clearly showed a mitochondrial genome.
These results show that here, at last, is a multicellular organism that doesn’t need oxygen to survive.
Exactly how it survives is still something of a mystery. It could be leeching adenosine triphosphate from its host, but that’s yet to be determined.
But the loss is pretty consistent with an overall trend in these creatures – one of genetic simplification. Over many, many years, they have basically devolved from a free-living jellyfish ancestor into the much more simple parasite we see today.
They’ve lost most of the original jellyfish genome, but retaining – oddly – a complex structure resembling jellyfish stinging cells. They don’t use these to sting, but to cling to their hosts: an evolutionary adaptation from the free-living jellyfish’s needs to the parasite’s. You can see them in the image above – they’re the things that look like eyes.
The discovery could help fisheries adapt their strategies for dealing with the parasite; although it’s harmless to humans, no one wants to buy salmon riddled with tiny weird jellyfish.
But it’s also a heck of a discovery for helping us to understand how life works.
“Our discovery confirms that adaptation to an anaerobic environment is not unique to single-celled eukaryotes, but has also evolved in a multicellular, parasitic animal,” the researchers wrote in their paper.
“Hence, H. salminicola provides an opportunity for understanding the evolutionary transition from an aerobic to an exclusive anaerobic metabolism.”
The research has been published in PNAS.
Elon Musk’s Starlink Is Causing More Streaks to Appear in Space Images – Gizmodo
Researchers at the Zwicky Transient Facility in California have analyzed the degree to which SpaceX’s Starlink satellite constellation is affecting ground-based astronomical observations. The results are mixed.
The new paper, published in The Astrophysical Journal Letters and led by former Caltech postdoctoral scholar Przemek Mróz, offers some good news and some bad news. The good news is that Starlink is not currently causing problems for scientists at the Zwicky Transient Facility (ZTF), which operates out of Caltech’s Palomar Observatory near San Diego. ZTF, using both optical and infrared wavelengths, scans the entire night sky once every two days in an effort to detect sudden changes in space, such as previously unseen asteroids and comets, stars that suddenly go dim, or colliding neutron stars.
But that doesn’t mean Starlink satellites, which provide broadband internet from low Earth orbit, aren’t having an impact. The newly completed study, which reviewed archival data from November 2019 to September 2021, found 5,301 satellite streaks directly attributable to Starlink. Not surprisingly, “the number of affected images is increasing with time as SpaceX deploys more satellites,” but, so far, science operations at ZTF “have not yet been severely affected by satellite streaks, despite the increase in their number observed during the analyzed period,” the astronomers write in their study.
The bad news has to do with the future situation and how satellite megaconstellations, whether Starlink or some other fleet, will affect astronomical observations in the years to come, particularly observations made during the twilight hours. Indeed, images most affected by Starlink were those taken at dawn or dusk. In 2019, this meant satellite streaks in less than 0.5% of all twilight images, but by August 2019 this had escalated to 18%. Starlink satellites orbit at a low altitude of around 324 miles (550 km), causing them to reflect more sunlight during sunset and sunrise, which creates a problem for observatories at twilight.
Astronomers perform observations at dawn and dusk when searching for near-Earth asteroids that might appear next to the Sun from our perspective. Two years ago, ZTF astronomers used this technique to detect 2020 AV2—the first asteroid entirely within the orbit of Venus. A concern expressed in the new paper is that, when Starlink gets to 10,000 satellites—which SpaceX expects to achieve by 2027—all ZTF images taken during twilight will contain at least one satellite streak. Following yesterday’s launch of a Falcon 9 rocket, the Starlink megaconstellation consists of over 2,000 satellites.
In a Caltech press release, Mróz, now at the University of Warsaw in Poland, said he doesn’t “expect Starlink satellites to affect non-twilight images, but if the satellite constellation of other companies goes into higher orbits, this could cause problems for non-twilight observations.” A pending satellite constellation managed by OneWeb, a UK-based telecommunications firm, will orbit at an operational altitude of 745 miles (1,200 km), for example.
The researchers also estimated the fraction of pixels that are lost as a result of a single satellite streak, finding it to be “not large.” By “not large” they mean 0.1% of all pixels in a single ZTF image.
That said, “simply counting pixels affected by satellite streaks does not capture the entirety of the problem, for example resources that are required to identify satellite streaks and mask them out or the chance of missing a first detection of an object,” the scientists write. Indeed, as Thomas Prince, an astronomer at Caltech and a co-author of the study pointed out in the press release, a “small chance” exists that “we would miss an asteroid or another event hidden behind a satellite streak, but compared to the impact of weather, such as a cloudy sky, these are rather small effects for ZTF.”
SpaceX has not responded to our request for comment.
The scientists also looked into the measures taken by SpaceX to reduce the brightness of Starlink satellites. Implemented in 2020, these measures include visors that prevent sunlight from illuminating too much of the satellite’s surface. These measures have served to reduce the brightness of Starlink satellites by a factor of 4.6, which means they’re now at a 6.8 magnitude (for reference, the brightest stars shine at a magnitude 1, and human eyes can’t see objects much dimmer than 6.0). This marks a major improvement, but it’s still not great, as members of the 2020 Satellite Constellations 1 workshop asked that satellites in LEO have magnitudes above 7.
The current study only considered the impacts of Starlink on the Zwicky Transient Facility. Every observatory will be affected differently by Starlink and other satellites, including the upcoming Vera C. Rubin Observatory, which is expected to be badly affected by megaconstellations. Observatories are also expected to experience problems as a result of radio interference, the appearance of ghost-like artifacts, among other potential issues.
Earth's core is rapidly cooling, study reveals. Is our planet becoming 'inactive'? – USA TODAY
Planet Earth hits 6th warmest year on record
Earth simmered to the sixth hottest year on record in 2021, according to several newly released temperature measurements. (Jan. 13)
Earth’s interior is cooling faster than we previously estimated, according to a recent study, prompting questions about how long people can live on the planet.
There’s no exact timetable on the cooling process, which could eventually turn Earth solid, similar to Mars. But results from a new study, published in the peer-reviewed journal Earth and Planetary Science Letters, focuses on how quickly the core may cool by studying bridgmanite, a heat-conducting mineral commonly found at the boundary between the Earth’s core and mantle.
“Our results could give us a new perspective on the evolution of the Earth’s dynamics,” ETH Zurich professor Motohiko Murakami, the lead author of the study, said in a press release. “They suggest that Earth, like the other rocky planets Mercury and Mars, is cooling and becoming inactive much faster than expected.”
While the process may be moving quicker than previously thought, it’s a timeline that “should be hundreds of millions or even billions of years,” Murakami told USA TODAY.
The boundary between the Earth’s outer core and mantle is where the planet’s internal heat interaction exists. The scientific team studied how much bridgmanite conducts from the Earth’s core and found higher heat flow is coming from the core into the mantle, dissipating the overall heat and cooling much faster than initially thought.
“This measurement system let us show that the thermal conductivity of bridgmanite is about 1.5 times higher than assumed,” Murakami said in the press release. “We still don’t know enough about these kinds of events to pin down their timing.”
Owning, not doing: my transition from master's to PhD student – Nature.com
One of the most important lessons I learnt from my seven years of graduate studies is the difference between simply ‘doing’ a research project and ‘owning’ one and how to make the transition from a doer to a researcher.
I started as very much a doer. During my master’s-degree work studying proteins involved in Alzheimer’s disease, at Wuhan University, China, I relied on my supervisor — biochemist Yi Liang — to assign me to a research project, to propose ideas and sometimes to plan out sets of experiments for me. I simply had to follow protocols and produce data. I would read papers, but just the most relevant ones on the particular protein I was studying, or those involving the same methods that I was using. When I read those papers, it was to benefit my own experiments: I wasn’t looking for any deeper knowledge or understanding.
There are advantages to this approach: once everything had been mapped out for me, I was well on my way to getting my name on a paper, thanks to the data contributions I’d made. But following instructions without developing a deep understanding is not how students become successful scientists, even if they get their name on a paper.
Doing versus owning a research project
My interest in protein structures continued during my PhD programme at the University of Western Ontario in London, Canada. At first, I maintained the mindset I had while pursuing my master’s: I devoted myself to laboratory work and generating data. My PhD supervisor, structural biologist Gary Shaw, didn’t give me the step-by-step instructions I was used to, however. This often confused me and made it hard for me to find an obvious way forward. Our discussions on the project always remained ‘open ended’, leaving uncertainties for me to solve and decisions for me to make.
So, instead of being told what to do next, I learnt how to think about what confused me. I tried to answer my questions by myself, and to increasingly dictate the path of my own research. My PhD supervisor constantly encouraged and empowered me to come up with ideas, proposals and experiments. He told me, “You should own your research project instead of just doing it. By the time you graduate, your goal is to be the most knowledgeable person about your research in the whole world.”
Road to owning your research
Owning my research project in this way was deeply intimidating at first: I no longer had a decision-maker with more experience to follow. But as I developed as a scientist by reading and thinking at a deeper level, and as my excitement grew from following my own curiosity, I overcame this feeling. By the time I ended the second year of my PhD programme, I felt much more confident in my abilities as a researcher — not just as a data-gatherer.
Owning my project triggered some deep thinking that further inspired me to establish hypotheses, methodologies and collaborations with researchers around the world. In the last year of my PhD programme, I e-mailed neuroscientist Sandra Cooper at the University of Sydney, Australia, to discuss a few technical questions about her 2017 publication in the Journal of Biological Chemistry1. She kindly connected me to computational biologist Bradley Williams at the Jain Foundation in Seattle, Washington.
This was the start of a long-term collaboration between our labs, and I got to learn a lot about computational biology from them. The collaboration changed the direction of my project to some extent and brought a completely new perspective to my research and my lab.
Here are some tips I’d give anyone who wants to learn to own their research project.
1. Think beyond day-to-day bench work. Even if most of your time is allocated to doing lab work, don’t let it take over and become the core of your work. Instead, spend time thinking about why you’re doing particular experiments. What are you trying to achieve? What can you learn? What information is missing? All lab work should be driven by a clear rationale based on the literature, and motivated by a desire to answer scientific questions.
2. Make short- and long-term plans. Your supervisor might plan for you sometimes, but it’s important to be your own pilot. Make to-do lists for each day, week and month, so you know what you’re expecting and what you should prioritize. By doing this, you will learn how to make adjustments and better manage your time. Set goals along the way and enjoy every achievement — big and small.
3. Use all available resources. Science should not be a lone battle. Your supervisor, your lab mates and people from other labs are all resources that can help you with your research. There’s also a rich store of online advice and tools you can use to support yourself. For example, I found great help from Q&A forums on ResearchGate, a social-networking website for scientists. Don’t shy away from initiating conversations with researchers outside your department or institution if you think they could be helpful.
4. Communicate your research. Discussing your research at seminars and conferences, and with members of the public, requires your full understanding of it: I found that speaking at conferences helped me to discover what I didn’t understand in my field. Communication sparks collaboration and allows you to look at your research in contexts you might have not considered, which could in turn inspire ideas.
Of course, self-directed research has downsides. It won’t always give you the best results. You’re also likely to go through more trial and error. Not all the data you collect will be publishable — and some of it might feel like it’s downright useless. Certainly, the road to get my PhD work published was a winding, bumpy one. But nothing is more rewarding than owning up to your failures, pushing past each obstacle and finding a way to move forward.
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