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Giant viruses found on Greenland ice sheet
![Giant viruses found on Greenland ice sheet Giant viruses found on Greenland ice sheet](https://www.sciencedaily.com/images/scidaily-icon.png)
Every spring when the sun rises in the Arctic after months of darkness, life returns. The polar bears pop up from their winter lairs, the arctic tern soar back from their long journey south and the musk oxen wade north.
When the ice blackens it’s ability to reflect the sun diminishes and this accelerates the melting of the ice. Increased melting exacerbates global warming.
But researchers might have found a way to control the snow algae growth — and maybe in the long run reduce some of the ice from melting. Living on the ice alongside the algae, postdoc Laura Perini from the Department of Environmental Science at Aarhus University and her colleagues, have found giant viruses.
She suspects that the viruses feed on the snow algae and could work as a natural control mechanism on the algae blooms.
“We don’t know a lot about the viruses, but I think they could be useful as a way of alleviating ice melting caused by algal blooms. How specific they are and how efficient it would be, we do not know yet. But by exploring them further, we hope to answer some of those questions,” she says.
Bigger than bacteria
Viruses are normally much smaller than bacteria. Regular viruses measure 20-200 nanometers in size, whereas a typical bacteria is 2-3 micrometers. In other words a normal virus is around 1000 times smaller than a bacteria.
That is not the case with giant viruses though.
Giant viruses grow to the size of 2.5 micrometers. That is bigger than most bacteria.
But the giant viruses are not only bigger in size. Their genome is much bigger than regular viruses. Bacteriophages — virus infecting bacteria — have between 100,000 and 200,000 letters in their genome. Giant viruses have around 2,500,000.
Never found on the ice before
Giant viruses were first discovered in 1981, when researchers found them in the ocean. These viruses had specialized in infecting green algae in the sea. Later, giant viruses were found in soil on land and even in humans.
But it’s the first time that giant viruses have been found living on the surface ice and snow dominated by microalgae, Laura Perini explains.
“We analyzed samples from dark ice, red snow and melting holes (cryoconite). In both the dark ice and red snow we found signatures of active giant viruses. And that is the first time they’ve been found on surface ice and snow containing a high abundance of pigmented microalgae.
“A few years ago everyone thought this part of the world to be barren and devoid of life. But today we know that several microorganisms live there — including the giant viruses.”
“There’s a whole ecosystem surrounding the algae. Besides bacteria, filamentous fungi and yeasts, there are protists eating the algae, different species of fungi parasitizing them and the giant viruses that we found, infecting them.
“In order to understand the biological controls acting on the algal blooms, we need to study these last three groups.”
Haven’t seen them with the naked eye
Even though the viruses are giant, they can’t be seen with the naked eye. Laura Perini hasn’t even seen them with a light microscope yet. But she hopes to do so in the future.
“The way we discovered the viruses was by analyzing all the DNA in the samples we took. By sifting through this huge dataset looking for specific marker genes, we found sequences that have high similarity to known giant viruses,” she explains.
To make sure that the viral DNA didn’t come from long dead microorganisms, but from living and active viruses, they also extracted all the mRNA from the sample.
When the sequences of the DNA that form genes are activated, they are transcribed into single stranded pieces called mRNA. These pieces work as recipes for building the proteins the virus needs. If they are present the virus is alive.
“In the total mRNA sequenced from the samples, we found the same markers as in the total DNA, so we know they have been transcribed. It means that the viruses are living and active on the ice,” she says.
DNA and RNA in viruses
At the center of the giant viruses is a cluster of DNA. That DNA contains all the genetic information or recipes needed to create proteins — the chemical compounds that are doing most of the work in the virus.
But in order to use those recipes, the virus needs to transcribe them from double-stranded DNA to single stranded mRNA.
Normal viruses can’t do that. Instead they have strands of RNA floating around in the cell waiting to be activated, when the virus infects an organism and hijacks its cellular production facilities.
Giant viruses can do that themselves which makes them very different from normal viruses.
Whereas DNA from dead viruses can be found in samples, mRNA is broken down much faster. mRNA is therefore an important marker of viral activity. In other words mRNA-recipes of certain proteins show that the viruses are alive and kicking.
Not sure exactly how they work
Because giant viruses are a relatively new discovery not a lot is known about them. In contrast to most other viruses they have a lot of active genes that enable them to repair, replicate, transcribe and translate DNA.
But why that is and exactly what they use it for is not known.
“Which hosts the giant viruses infect, we can’t link exactly. Some of them may be infecting protists while others attack the snow algae. We simply can’t be sure yet,” Laura Perini says.
She’s working hard on discovering more about the giant viruses and has more research coming out soon.
“We keep studying the giant viruses to learn more about their interactions and what is exactly is their role in the ecosystem. Later this year we’ll release another scientific with some more info on giant viruses infecting a cultivated microalgae thriving on the surface ice of the Greenland Ice Sheet,” she concludes.
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‘Ice bucket challenge’ reveals that bacteria can anticipate the seasons
![Giant viruses found on Greenland ice sheet Giant viruses found on Greenland ice sheet](https://www.sciencedaily.com/images/scidaily-icon.png)
Bacteria use their internal 24-hour clocks to anticipate the arrival of new seasons, according to research carried out with the assistance of an ‘ice bucket challenge.’
The team behind the findings gave populations of blue-green algae (cyanobacteria) different artificial day lengths at a constant warm temperature. Samples on plates received either short days, equinox days (equal light and dark), or long days, for eight days.
After this treatment, the blue-green algae were plunged into ice for two hours and survival rates monitored.
Samples that had been exposed to a succession of short days (eight hours light and 16 hours dark) in preparation for the icy challenge achieved survival rates of 75%, up to three times higher than colonies that had not been primed in this way.
One short day was not enough to increase the bacteria’s resistance to cold. Only after several short days, and optimally six to eight days, did the bacteria’s life chances significantly improve.
In cyanobacteria which had genes that make up their biological clock removed, survival rates were the same regardless of day lengths. This indicates that photoperiodism (the ability to measure the day-night cycle and change one’s physiology in anticipation of the upcoming season) is critical in preparing bacteria for longer-term environmental changes such as a new season or shifts in climate.
“The findings indicate that bacteria in nature use their internal clocks to measure day length and when the number of short days reaches a certain point, as they do in autumn/fall, they ‘switch’ to a different physiology in anticipation of the wintry challenges that lie ahead,” explained first author of the study, Dr Luísa Jabbur, who was a researcher at Vanderbilt University, Tennessee, in the laboratory of Prof. Carl Johnson when this study took place, and is now a BBSRC Discovery Fellow at the John Innes Centre.
The Johnson lab has a long history of studying the circadian clock of cyanobacteria, both from a mechanistic and an ecological perspective.
Previous studies have shown that bacteria have a version of a biological clock, which could allow them to measure differences in day-night length, offering an evolutionary advantage.
This study, which appears in Science, is the first time that anyone has shown that photoperiodism in bacteria has evolved to anticipate seasonal cues.
Based on these findings a whole new horizon of scientific exploration awaits. A key question is: how does an organism with a lifespan of between six and 24 hours evolve a mechanism that enables it not merely to react to, but to anticipate, future conditions?
“It’s like they are signalling to their daughter cells and their granddaughter cells, passing information that the days are getting short, you need to do something,” said Dr Jabbur.
Dr Jabbur and colleagues at the John Innes Centre will, as part of her BBSRC Discovery Fellowship, use cyanobacteria as a fast-reproducing model species to understand how photoperiodic responses might evolve in other species during climate change, with hopeful applications to major crops.
A key part of this work will be to understand more about the molecular memory systems by which information is passed from generation to generation in species. Research will investigate the possibility that an accumulation of compounds during the night on short days acts as a molecular switch that triggers change to a different physiology or phenotype.
For Dr Jabbur the findings amount to an early-career scientific breakthrough in the face of initial scepticism from her scientific mentor and the corresponding author of the paper, Professor Carl Johnson.
“As well as being a fascinating person and an inspiration, Carl sings in the Nashville Symphony Chorus, and he has an operatic laugh! It echoed round the department when I first outlined my idea for the icy challenge, to see if photoperiod was a cue for cyanobacteria in their natural element,” said Dr Jabbur.
“To be fair he told me to go away and try it, and as I went, he showed me a sign on his door with the Frank Westheimer quote: ‘Progress is made by young scientists who carry out experiments that old scientists say would not work.’
“It did work, first time. Then I repeated the experiments. There is something very precious about looking at a set of plates with bacteria on them and realizing that in that moment you know something that nobody else knows.”
Bacteria can anticipate the seasons: Photoperiodism in cyanobacteria appears in Science.
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New filtration material could remove long-lasting chemicals from water
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Water contamination by the chemicals used in today’s technology is a rapidly growing problem globally. A recent studyby the U.S. Centers for Disease Control found that 98 percent of people tested had detectable levels of PFAS, a family of particularly long-lasting compounds, also known as forever chemicals, in their bloodstream.
The findings are described in the journal ACS Nano, in a paper by MIT postdoc Yilin Zhang, professor of civil and environmental engineering Benedetto Marelli, and four others from MIT.
PFAS chemicals are present in a wide range of products, including cosmetics, food packaging, water-resistant clothing, firefighting foams, and antistick coating for cookware. A recent study identified 57,000 sites contaminated by these chemicals in the U.S. alone. The U.S. Environmental Protection Agency has estimated that PFAS remediation will cost $1.5 billion per year, in order to meet new regulations that call for limiting the compound to less than 7 parts per trillion in drinking water.
Contamination by PFAS and similar compounds “is actually a very big deal, and current solutions may only partially resolve this problem very efficiently or economically,” Zhang says. “That’s why we came up with this protein and cellulose-based, fully natural solution,” he says.
“We came to the project by chance,” Marelli notes. The initial technology that made the filtration material possible was developed by his group for a completely unrelated purpose — as a way to make a labelling system to counter the spread of counterfeit seeds, which are often of inferior quality. His team devised a way of processing silk proteins into uniform nanoscale crystals, or “nanofibrils,” through an environmentally benign, water-based drop-casting method at room temperature.
Zhang suggested that their new nanofibrillar material might be effective at filtering contaminants, but initial attempts with the silk nanofibrils alone didn’t work. The team decided to try adding another material: cellulose, which is abundantly available and can be obtained from agricultural wood pulp waste. The researchers used a self-assembly method in which the silk fibroin protein is suspended in water and then templated into nanofibrils by inserting “seeds” of cellulose nanocrystals. This causes the previously disordered silk molecules to line up together along the seeds, forming the basis of a hybrid material with distinct new properties.
By integrating cellulose into the silk-based fibrils that could be formed into a thin membrane, and then tuning the electrical charge of the cellulose, the researchers produced a material that was highly effective at removing contaminants in lab tests.
The electrical charge of the cellulose, they found, also gave it strong antimicrobial properties. This is a significant advantage, since one of the primary causes of failure in filtration membranes is fouling by bacteria and fungi. The antimicrobial properties of this material should greatly reduce that fouling issue, the researchers say.
“These materials can really compete with the current standard materials in water filtration when it comes to extracting metal ions and these emerging contaminants, and they can also outperform some of them currently,” Marelli says. In lab tests, the materials were able to extract orders of magnitude more of the contaminants from water than the currently used standard materials, activated carbon or granular activated carbon.
While the new work serves as a proof of principle, Marelli says, the team plans to continue working on improving the material, especially in terms of durability and availability of source materials. While the silk proteins used can be available as a byproduct of the silk textile industry, if this material were to be scaled up to address the global needs for water filtration, the supply might be insufficient. Also, alternative protein materials may turn out to perform the same function at lower cost.
Initially, the material would likely be used as a point-of-use filter, something that could be attached to a kitchen faucet, Zhang says. Eventually, it could be scaled up to provide filtration for municipal water supplies, but only after testing demonstrates that this would not pose any risk of introducing any contamination into the water supply. But one big advantage of the material, he says, is that both the silk and the cellulose constituents are considered food-grade substances, so any contamination is unlikely.
“Most of the normal materials available today are focusing on one class of contaminants or solving single problems,” Zhang says. “I think we are among the first to address all of these simultaneously.”
The research team included MIT postdocs Hui Sun and Meng Li, graduate student Maxwell Kalinowski, and recent graduate Yunteng Cao PhD ’22, now a postdoc at Yale. The work was supported by the Office of Naval Research, the National Science Foundation, and the Singapore-MIT Alliance for Research and Technology.
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‘Some pterosaurs would flap, others would soar’ — new study further confirms the flight capability of these giants of the skies
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Some species of pterosaurs flew by flapping their wings while others soared like vultures, demonstrates a new study published in the peer-reviewed Journal of Vertebrate Paleontology.
However, “remarkable” and “rare” three-dimensional fossils of two different large-bodied azhdarchoid pterosaur species — including one new-to-science — have enabled scientists to hypothesize that not only could the largest pterosaurs take to the air, but their flight styles could differ too.
The new findings are led by experts from the University of Michigan, in the US, the Natural Resources Authority and Yarmouk University, in Jordan, and the Saudi Geological Survey, in Saudi Arabia.
Their paper details how these fossils — which date back to the latest Cretaceous period (approximately 72 to 66 million years ago) — were remarkably three-dimensionally preserved within the two different sites that preserve a nearshore environment on the margin of Afro-Arabia, an ancient landmass that included both Africa and the Arabian Peninsula. The research team used high-resolution computed tomography (CT) scans to then analyze the internal structure of the wing bones.
“The dig team was extremely surprised to find three-dimensionally preserved pterosaur bones, this is a very rare occurrence,” explains lead author Dr Kierstin Rosenbach, from the Department of Earth and Environmental Sciences of the University of Michigan.
“Since pterosaur bones are hollow, they are very fragile and are more likely to be found flattened like a pancake, if they are preserved at all.
“With 3D preservation being so rare, we do not have a lot of information about what pterosaur bones look like on the inside, so I wanted to CT scan them.
“It was entirely possible that nothing was preserved inside, or that CT scanners were not sensitive enough to differentiate fossil bone tissue from the surrounding matrix.”
Luckily, though, what the team uncovered was “remarkable,” via “exciting internal structures not only preserved, but visible in the CT scanner.”
CT scans reveal one soars; one flaps!
Newly collected specimens of the already-known giant pterosaur, Arambourgiania philadelphiae, confirm its 10-meter wingspan and provide the first details of its bone structure. CT images revealed that the interior of its humerus, which is hollow, contains a series of ridges that spiral up and down the bone.
This resembles structures in the interior of wing bones of vultures. The spiral ridges are hypothesized to resist the torsional loadings associated with soaring (sustained powered flight that requires launch and maintenance flapping).
The other specimen analyzed was the new-to-science Inabtanin alarabia, which had a five-meter wingspan. The team named it after the place where it was excavated — near a large grape-colored hill, called Tal Inab. The generic name combines the Arabic words “inab,” for grape, and “tanin” for dragon. ‘Alarabia’ refers to the Arabian Peninsula.
Inabtanin is one of the most complete pterosaurs ever recovered from Afro-Arabia, and the CT scans revealed the structure of its flight bones was completely different from that of Arambourgiania.
The interior of the flight bones were crisscrossed by arrangement with struts that match those found in the wing bones of modern flapping birds.
This indicates it was adapted to resist bending loads associated with flapping flight, and so it is likely that Inabtanin flew this way — although this does not preclude occasional use of other flight styles too.
“The struts found in Inabtanin were cool to see, though not unusual,” says Dr Rosenbach.
“The ridges in Arambourgiania were completely unexpected, we weren’t sure what we were seeing at first!
“Being able to see the full 3D model of Arambourgiania’s humerus lined with helical ridges was just so exciting.”
What explains this difference?
The discovery of diverse flight styles in differently-sized pterosaurs is “exciting,” the experts state, because it opens a window into how these animals lived. It also poses interesting questions, like to what extent flight style is correlated with body size and which flight style is more common among pterosaurs.
“There is such limited information on the internal bone structure of pterosaurs across time, it is difficult to say with certainty which flight style came first,” Dr Rosenbach adds.
“If we look to other flying vertebrate groups, birds and bats, we can see that flapping is by far the most common flight behavior.
“Even birds that soar or glide require some flapping to get in the air and maintain flight.
“This leads me to believe that flapping flight is the default condition, and that the behavior of soaring would perhaps evolve later if it were advantageous for the pterosaur population in a specific environment; in this case the open ocean.”
Co-author Professor Jeff Wilson Mantilla, Curator at Michigan’s Museum of Paleontology, and Dr Iyad Zalmout, from the Saudi Geological Survey, found these specimens in 2007 at sites in the north and south of Jordan.
Professor Jeff Wilson Mantilla says the “variations likely reflect responses to mechanical forces applied on the pterosaurs’ wings during flight.”
Enabling further study of vertebrate flight
Concluding, Dr Rosenbach states: “Pterosaurs were the earliest and largest vertebrates to evolve powered flight, but they are the only major volant group that has gone extinct.
“Attempts to-date to understand their flight mechanics have relied on aerodynamic principles and analogy with extant birds and bats.
“This study provides a framework for further investigation of the correlation between internal bone structure and flight capacity and behavior, and will hopefully lead to broader sampling of flight bone structure in pterosaur specimens.”
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