Meteorite analysis shows reduced salt is key in Earth's new recipe

This is a reflected light image of a metal-sulphide clast in the enstatite chondrite ALH 77295. The central portion of the clast is a mineral called djerfisherite, an important host for chlorine in these meteorites.

Scientists have found the halogen levels in the meteorites that formed the Earth billions of years ago are much lower than previously thought.

The research was carried out by international team of researchers, led by the Universities of Manchester and Oxford, and has recently been published in Nature.

Halogens such as Chlorine, Bromine and Iodine, form naturally occurring salts which are essential for most life forms -- but too much can prohibit life. When previously comparing halogen levels in meteorites that formed the planet, the Earth should have unhealthy levels of salt.

Many theories have been put forward to explain the mystery of why, instead, Earth salt concentrations are 'just right'. The answer turns out to be quite simple -- previous estimates meteorites were just too high.

Using a new analytical technique, the team looked at different kinds of chondrite meteorites, a type of primitive meteorite approximately 4.6 billion years old.

Dr Patricia Clay, lead author of the study from the University of Manchester's School of Earth and Environmental Sciences (SEES), said: 'These kinds of meteorites are remnants of the solar nebula, a molecular cloud made up of interstellar dust and hydrogen gas that predates our Solar System. Studying them provides important clues for our understanding of the origin and age of the Solar System.'

How the Earth acquired its volatile elements has long interested scientists. To answer the question the team re-examined one of the largest collection of meteorites assembled for this type of study.

They found that previous estimates of halogen levels in meteorites were too high, but the technique used by the team helped them avoid contaminated sources.

Dr Clay explains: "No single model of Earth formation using the old meteorite measurements could easily account for the halogens we see today. Some of these models needed catastrophic planetary wide removal of halogens without affecting related elements -- which just didn't make sense."

Professor Ray Burgess, co-author and also from The University of Manchester, added: "The new simplified model we have developed is a big step forward in understanding how key ingredients essential for life were brought to our planet, including water that probably helped distribute the halogens between the planetary interior and surface."

The results were a huge surprise, and time after time each meteorite measured was found to have halogen levels far lower than previously thought, and remarkably consistent between different types of meteorites.

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Engineers 3-D print a 'living tattoo'

MIT engineers have devised a 3-D printing technique that uses a new kind of ink made from genetically programmed living cells.

MIT engineers have devised a 3-D printing technique that uses a new kind of ink made from genetically programmed living cells.

The cells are engineered to light up in response to a variety of stimuli. When mixed with a slurry of hydrogel and nutrients, the cells can be printed, layer by layer, to form three-dimensional, interactive structures and devices.

The team has then demonstrated its technique by printing a "living tattoo" -- a thin, transparent patch patterned with live bacteria cells in the shape of a tree. Each branch of the tree is lined with cells sensitive to a different chemical or molecular compound. When the patch is adhered to skin that has been exposed to the same compounds, corresponding regions of the tree light up in response.

The researchers, led by Xuanhe Zhao, the Noyce Career Development Professor in MIT's Department of Mechanical Engineering, and Timothy Lu, associate professor of biological engineering and of electrical engineering and computer science, say that their technique can be used to fabricate "active" materials for wearable sensors and interactive displays. Such materials can be patterned with live cells engineered to sense environmental chemicals and pollutants as well as changes in pH and temperature.

What's more, the team developed a model to predict the interactions between cells within a given 3-D-printed structure, under a variety of conditions. The team says researchers can use the model as a guide in designing responsive living materials.

Zhao, Lu, and their colleagues have published their results today in the journal Advanced Materials. The paper's co-authors are graduate students Xinyue Liu, Hyunwoo Yuk, Shaoting Lin, German Alberto Parada, Tzu-Chieh Tang, Eléonore Tham, and postdoc Cesar de la Fuente-Nunez.

A hardy alternative

In recent years, scientists have explored a variety of responsive materials as the basis for 3D-printed inks. For instance, scientists have used inks made from temperature-sensitive polymers to print heat-responsive shape-shifting objects. Others have printed photoactivated structures from polymers that shrink and stretch in response to light.

Zhao's team, working with bioengineers in Lu's lab, realized that live cells might also serve as responsive materials for 3D-printed inks, particularly as they can be genetically engineered to respond to a variety of stimuli. The researchers are not the first to consider 3-D printing genetically engineered cells; others have attempted to do so using live mammalian cells, but with little success.

"It turns out those cells were dying during the printing process, because mammalian cells are basically lipid bilayer balloons," Yuk says. "They are too weak, and they easily rupture."

Instead, the team identified a hardier cell type in bacteria. Bacterial cells have tough cell walls that are able to survive relatively harsh conditions, such as the forces applied to ink as it is pushed through a printer's nozzle. Furthermore, bacteria, unlike mammalian cells, are compatible with most hydrogels -- gel-like materials that are made from a mix of mostly water and a bit of polymer. The group found that hydrogels can provide an aqueous environment that can support living bacteria.

The researchers carried out a screening test to identify the type of hydrogel that would best host bacterial cells. After an extensive search, a hydrogel with pluronic acid was found to be the most compatible material. The hydrogel also exhibited an ideal consistency for 3-D printing.

"This hydrogel has ideal flow characteristics for printing through a nozzle," Zhao says. "It's like squeezing out toothpaste. You need [the ink] to flow out of a nozzle like toothpaste, and it can maintain its shape after it's printed."

From tattoos to living computers

Lu provided the team with bacterial cells engineered to light up in response to a variety of chemical stimuli. The researchers then came up with a recipe for their 3-D ink, using a combination of bacteria, hydrogel, and nutrients to sustain the cells and maintain their functionality.

"We found this new ink formula works very well and can print at a high resolution of about 30 micrometers per feature," Zhao says. "That means each line we print contains only a few cells. We can also print relatively large-scale structures, measuring several centimeters."

They printed the ink using a custom 3-D printer that they built using standard elements combined with fixtures they machined themselves. To demonstrate the technique, the team printed a pattern of hydrogel with cells in the shape of a tree on an elastomer layer. After printing, they solidified, or cured, the patch by exposing it to ultraviolet radiation. They then adhere the transparent elastomer layer with the living patterns on it, to skin.

To test the patch, the researchers smeared several chemical compounds onto the back of a test subject's hand, then pressed the hydrogel patch over the exposed skin. Over several hours, branches of the patch's tree lit up when bacteria sensed their corresponding chemical stimuli.

The researchers also engineered bacteria to communicate with each other; for instance they programmed some cells to light up only when they receive a certain signal from another cell. To test this type of communication in a 3-D structure, they printed a thin sheet of hydrogel filaments with "input," or signal-producing bacteria and chemicals, overlaid with another layer of filaments of an "output," or signal-receiving bacteria. They found the output filaments lit up only when they overlapped and received input signals from corresponding bacteria .

Yuk says in the future, researchers may use the team's technique to print "living computers" -- structures with multiple types of cells that communicate with each other, passing signals back and forth, much like transistors on a microchip.

"This is very future work, but we expect to be able to print living computational platforms that could be wearable," Yuk says.

For more near-term applications, the researchers are aiming to fabricate customized sensors, in the form of flexible patches and stickers that could be engineered to detect a variety of chemical and molecular compounds. They also envision their technique may be used to manufacture drug capsules and surgical implants, containing cells engineered produce compounds such as glucose, to be released therapeutically over time.

Read more at Science Daily

Two Super-Earths around red dwarf K2-18

The ESO 3.6-metre telescope at La Silla.

New research using data collected by the European Southern Observatory (ESO) has revealed that a little-known exoplanet called K2-18b could well be a scaled-up version of Earth.

Just as exciting, the same researchers also discovered for the first time that the planet has a neighbor.

"Being able to measure the mass and density of K2-18b was tremendous, but to discover a new exoplanet was lucky and equally exciting," says lead author Ryan Cloutier, a PhD student in U of T Scarborough's Centre for Planet Science, U of T's Department of Astronomy and Astrophysics, and Université de Montréal Institute for research on exoplanets (iREx).

Both planets orbit K2-18, a red-dwarf star located about 111 light years away in the constellation Leo. When the planet K2-18b was first discovered in 2015, it was found to be orbiting within the star's habitable zone, making it an ideal candidate to have liquid surface water, a key element in harbouring conditions for life as we know it.

The data set used by the researchers came from the High Accuracy Radial Velocity Planet Searcher (HARPS) using the ESO's 3.6m telescope at La Silla Observatory, in Chile. HARPS allows for measurements of radial velocities of stars, which can be affected by the presence of nearby planets, to be taken with the highest accuracy currently available. The instrument makes it possible to detect very small planets orbiting those stars.

In order to figure out whether K2-18b was a scaled-up version of Earth (mostly rock), or a scaled-down version of Neptune (mostly gas), researchers had to first figure out the planet's mass, using radial velocity measurements taken with HARPS.

"If you can get the mass and radius, you can measure the bulk density of the planet and that can tell you what the bulk of the planet is made of," says Cloutier.

After using a machine-learning approach to figure out the mass measurement, Cloutier and his team were able to determine the planet is either a mostly rocky planet with a small gaseous atmosphere -- like Earth, but bigger -- or a mostly water planet with a thick layer of ice on top of it.

"With the current data, we can't distinguish between those two possibilities," he says. "But with the James Webb Space Telescope (JWST) we can probe the atmosphere and see whether it has an extensive atmosphere or it's a planet covered in water."

The JWST, which will be launched in 2019, will be instrumental in collecting a range of data for studying the solar system, early universe and exoplanets.

"There's a lot of demand to use this telescope, so you have to be meticulous in choosing which exoplanets to look at," says René Doyon, a co-author on the paper who is also the principal investigator for NIRISS, the Canadian Space Agency instrument on board JWST.

"K2-18b is now one of the best targets for atmospheric study, it's going to the near top of the list."

It was while looking through the data of K2-18b that Cloutier noticed something unusual. In addition to a signal occurring every 39 days from the rotation of K2-18, and one taking place every 33 days from the orbit of K2-18b, he noticed a different signal occurring every nine days.

"When we first threw the data on the table we were trying to figure out what it was. You have to ensure the signal isn't just noise, and you need to do careful analysis to verify it, but seeing that initial signal was a good indication there was another planet," Cloutier says.

Cloutier collaborated with an international team of researchers from the Observatoire Astronomique de l'Universite? de Gene?ve, the Institute for research on exoplanets (iREx), Universite? de Grenoble, U of T Scarborough, and Universidade do Porto.

While the newly described planet K2-18c is closer to its star, and probably too hot to be in the habitable zone, like K2-18b it also appears to be a Super-Earth meaning it has a mass similar to Earth. Cloutier, who had set the goal of discovering a new exoplanet within his PhD, considers himself very lucky to have discovered it in this dataset.

Read more at Science Daily

Earthworms Appear to Be Thriving in Simulated Martian Soil

Mars gardens simulation

In what could be an important milestone for future farmers on Mars, two healthy baby worms were recently born in simulated Martian soil. The births took place in an experiment that is helping scientists understand how human settlers might one day grow crops on the Red Planet.

Wieger Wamelink, a biologist at Wageningen University and Research Center in the Netherlands, is running plant growth experiments in a mixture of NASA-made Martian soil simulants — made from volcanic terrestrial rocks — and pig manure, to which he added live adult worms. University officials said in a statement that the infant worms are the first offspring of adult worms to be born in a Mars soil simulant.

Mars is not a naturally habitable environment for life as we know it, so if humans want to live there long term, Red Planet settlers will have to establish closed ecosystem models. (These are essentially large terrariums where factors like temperature and atmospheric moisture can be controlled.) According to the statement, those ecosystems will ideally utilize available waste materials, including human excrement and dead organic matter. That's where the worms come in.

Worms begin the breakdown of organic matter, which is continued by bacteria. That leads to the release into the soil of such vital plant nutrients as nitrogen, phosphorous, and potassium, according to the statement from Wageningen University and Research Center.

Illustration of potential appearance of a closed agricultural ecosystem on Mars

The researchers also found that the holes that worms dig in the soil aerate the mixture and improve the soil's structure, making it easier for water to penetrate the soil and nourish plants.

The appearance of baby worms seems to indicate that at least in the short term, the worms are thriving in these closed ecosystems.

The goal of the experiment is to find out how well worms break down old waste to produce food for bacteria and plants in the mixture of soil simulant and pig slurry (or manure). Various flowering plants were allowed to germinate in several pots of this mix, and adult worms were then added.

Simulated "Martian gardens" allow NASA scientists to test which plants can be grown on Mars. This photo shows the results of a preliminary study on lettuce. From left to right: lettuce seeds grown in potting soil, the Martian simulant with added nutrients, and the simulant without nutrients.

A crowdfunding campaign has been launched to continue experiments on these hardy worms. "Worms for Mars" has already raised more than half their funding goal of €10K, and with the public's help, Wageningen University and Research hopes to continue testing out different crops along with their crawling assistants. There is the possibility that sharp edges in non-Earth soil could damage the guts of the critters, the researchers said in another statement.

Read more at Seeker

Amniotic fluid is a rich source of stem cells that can now be harvested

Culturing cells in tissue culture plates.

Amniotic fluid, the protective liquid surrounding an unborn baby, is discarded as medical waste during caesarean section deliveries. However, there is increasing evidence that this fluid is a source of valuable biological material, including stem cells with the potential for use in cell therapy and regenerative medicine. A team of scientists and clinicians at Lund University in Sweden have now developed a multi-step method, including a unique collection device and new cell harvesting and processing techniques, that enables term amniotic fluid to be safely harvested for large quantities of cells.

The new method is used in combination with full-term caesarean section deliveries, and with millions of caesarean sections performed worldwide each year, it opens the potential for an unexploited reserve of stem cells and valuable bioactive molecules in the fluid surrounding the baby to be utilized.

"We showed that using our device, we can collect up to a litre of amniotic fluid at full-term caesarean deliveries. The collection added on average 90 seconds to the operation, and was safe for both mother and child," says Associate Professor Andreas Herbst, lead clinician and a corresponding author of the study.

The collection device, which has been constructed with bio-inert plastics and 3D-printing techniques, forms a seal with the fetal cavity, enabling gentle and sterile collection of large volumes of amniotic fluid, while being completely safe for mother and baby. The collected fluid contains specialized cells with high therapeutic potential. The cell type that the current protocol purifies is called a Mesenchymal Stem Cell (MSC).

MSCs can obtained from other tissues in the body, and have already demonstrated therapeutic potential for immune and inflammatory-mediated diseases, for example, cardiovascular disease, diabetes, arthritis, and neurodegenerative disorders. However, the difficulty in acquiring sufficient numbers of these cells limits their broad use in cell therapy and tissue repair applications. "Full term amniotic fluid, being an easily obtainable and abundant tissue source, may be the solution for MSC based cell therapy and regenerative medicine applications," says Associate Professor Niels-Bjarne Woods, a corresponding author in the study.

Since the collections involve planned Caesarean sections, no additional invasive medical procedures are needed for the MSC isolation, in contrast to MSC isolation from bone marrow.

The research group has also shown another potential use for MSCs purified from full-term amniotic fluid. By converting these cells to an embryonic-like stem cell state, they can potentially give rise to all different cell types of the body, including neural cells, blood cells and heart cells, among others.

"The combination of this novel device and the coupled cellular selection and cultivation methods could be transformative for the stem cell field, as large quantities of newborn-MSC's can be provided by utilizing this waste material. The safety standards we adhere to are also a central component for gaining clinical acceptance. The obvious next step would be to evaluate these cells further in the laboratory and, if successful, in disease models," says Dr Marcus Larsson, clinician and a corresponding author on the publication.

The long-term goal is that amniotic fluid collection will be adopted in clinics worldwide, and by doing so, the numbers of suitably matched MSCs obtained would rapidly increase to finally be sufficient to treat any genetically matched person in need of individualized MSC based therapy.

Read more at Science Daily

Invasive plants have unprecedented ability to pioneer new continents and climates

Velvetleaf represents one of the many invasive plant species that was tested by Dan Atwater and Jacob Barney.

It's no secret that globalization, aided by climate change, is helping invasive species gain a foothold across the planet. What came as something of a surprise to Virginia Tech researchers was just how mutable these invaders are.

The scientists discovered that invasive plant species are not only highly adaptive, they are essentially able to change in order to thrive on new continents and in different types of climates, challenging the assumption that species occupy the same environment in native and invasive ranges.

The study, by Jacob Barney, an associate professor in the College of Agriculture and Life Sciences' Department of Plant Pathology, Physiology, and Weed Science and Dan Atwater, a lecturer in the Department of Biological Sciences at North Carolina State University and Barney's former post-doctoral advisee, was published Tuesday in Nature Ecology and Evolution, an online journal.

"This is important for both changing how we think about species and where they grow," said Barney, who is also a fellow in the Fralin Life Science Institute and an affiliate of the Global Change Center. "The findings also change our ability to predict where they will grow, and how they may respond in a changing climate. This could be a game-changer for invasive species risk assessment and conservation."

Atwater used data compiled by undergraduate Carissa Ervine, also an author on the paper, to test a long-held assumption in ecology -- that the climate limitations of plants do not change, which means we can predict where they will grow. Small studies supported this supposition. However, the Virginia Tech researchers blew this assumption away by testing more than 800 species using new models developed by Atwater and Barney.

"Some people would say that invasive species have different distributions in a new climate. But we found they are occupying a wider range of new climates," said Atwater. "Species are changing in their ecology when they move from one continent to another. We should expect species to change, possibly permanently, when they cross continents."

The results have major consequences for applying environmental niche models to assess the risk of invasive species and for predicting species' responses to climate change. Species capable of changing their ecology and the climates they call home may pose a challenge to researchers using native range data to forecast the distribution of invasive species.

The driver behind the study was a desire to forecast the future distribution of invasive species which pose a serious threat to human, environmental, and economic health. The researchers began by posing the question: Do invasive species occupy the same climate in invasive range that they do in their native range? To find out, they compared native and invasive species.

Barney and Atwater examined 815 terrestrial plant species from every continent, along with millions of occurrence points, or locations where the plants have been known to occur, and compared models in the largest global invasive species study to date. They found evidence of climatic niche shifts in all of the 815 plant species introduced across five continents. A climatic niche refers to the set of climates in which a species has a stable or growing population.

Generally, their findings suggest that niche shifts reflect changes in climate availability at the continent scale and were the largest in long-lived and cultivated species. If species move to a warmer continent, for instance, they tend to shift towards occupying warmer climates. In short, cultivated plants with long lifespans are particularly adept at making themselves home in brand new climates.

"There are not only implications for predicting where invasive species will occur, there are management repercussions as well," said Barney. "As an example, for certain species we use biocontrol, introducing one organism to control another, an approach that may not be effective or safe if the targeted species undergoes ecological change. When we do climate modeling, we assume the climate niche may be the same when it may not be. So, there are a broad range of implications in a broad range of fields."

Barney raised another concern.

"By cultivating species -- bending them for agricultural or ornamental purposes and selecting for traits such as cold-hardiness, we push them into environments they would not have occupied," he said. "Those selection pressures in breeding, plus the environments we put them in, may exaggerate this change. Short-lived species, for example, go into dryer climates. So the take home is that different species' traits influence the direction of a niche shift."

Once Atwater and Barney understand these drivers more fully, they hope to be able to predict how the geographic range of an invasive species will increase in order to pinpoint areas likely to be invaded.

"The other piece layered onto this is the assumption that the climate is stable, which is not the case," said Atwater. "We have also relied on the assumption that a species is a species and its ecological tendencies remain constant. This too is not the case. Species vary in space and time. They behave differently on different continents and in different climates. Consequently, the concept of a species climatic niche is less stable and less clearly defined."

Read more at Science Daily

Possibility of plate tectonics on Jupiter's moon Europa bolstered

Previous studies had hinted that something like subduction may have been happening on Jupiter's moon, Europa. A new study provides geophysical evidence that it could indeed be happening on the moon's icy shell.

A Brown University study provides new evidence that the icy shell of Jupiter's moon Europa may have plate tectonics similar to those on Earth. The presence of plate tectonic activity could have important implications for the possibility of life in the ocean thought to exist beneath the moon's surface.

The study, published in Journal of Geophysical Research: Planets, uses computer modeling to show that subduction -- when a tectonic plate slides underneath another and sinks deep into a planet's interior -- is physically possible in Europa's ice shell. The findings bolster earlier studies of Europa's surface geology that found regions where the moon's ice shell looks to be expanding in a way that's similar to the mid-ocean spreading ridges on Earth. The possibility of subduction adds another piece to the tectonic puzzle.

"We have this evidence of extension and spreading, so the question becomes where does that material go?" said Brandon Johnson, an assistant professor in Brown's Department of Earth, Environmental and Planetary Sciences and a lead author of the study. "On Earth, the answer is subduction zones. What we show is that under reasonable assumptions for conditions on Europa, subduction could be happening there as well, which is really exciting."

Part of the excitement, Johnson says, is that surface crust is enriched with oxidants and other chemical food for life. Subduction provides a means for that food to come into contact with the subsurface ocean scientists think probably exists under Europa's ice.

"If indeed there's life in that ocean, subduction offers a way to supply the nutrients it would need," Johnson said.

Subduction on ice

On Earth, subduction is driven largely by differences in temperature between a descending slab and the surrounding mantle. Crustal material is much cooler than mantle material, and therefore denser. That increased density provides the negative buoyancy needed to sink a slab deep into the mantle.

Though previous geological studies had hinted that something like subduction could be happening on Europa, it wasn't clear exactly how that process would work on an icy world. There's evidence, Johnson says, that Europa's ice shell has a two layers: a thin outer lid of very cold ice that sits atop a layer of slightly warmer, convecting ice. If a plate from the outer ice lid was pushed down into the warmer ice below, its temperature would quickly warm to that of the surrounding ice. At the point, the slab would have the same density of the surrounding ice and would therefore stop descending.

But the model developed by Johnson and his colleagues showed a way that subduction could happen on Europa, regardless of temperature differences. The model showed that if there were varying amounts of salt in the surface ice shell, it could provide the necessary density differences for a slab to subduct.

"Adding salt to an ice slab would be like adding little weights to it because salt is denser than ice," Johnson said. "So rather than temperature, we show that differences in the salt content of the ice could enable subduction to happen on Europa."

And there's good reason to suspect that variations in salt content do exist on Europa. There's geological evidence for occasional water upwelling from Europa's subsurface ocean -- a process similar to the upwelling of magma from Earth's mantle. That upwelling would leave high salt content in the crust under which it rises. There's also a possibility of cryovolcanism, where salty ocean contents actually spray out onto the surface.

In addition to bolstering the case for a habitable ocean on Europa, Johnson says, the research also suggests a new place in the solar system to study a process that's played a crucial role in the evolution of our own planet.

"It's fascinating to think that we might have plate tectonics somewhere other than Earth," he said. "Thinking from the standpoint of comparative planetology, if we can now study plate tectonics in this very different place, it might be able to help us understand how plate tectonics got started on the Earth."

Read more at Science Daily

Surprise in the kangaroo family tree

The swamp wallaby (Wallabia bicolor) is more closely related to the remaining wallaby species and the large red and grey kangaroos and wallaroos than previously assumed.

Ironically, it is jumping genes that indicate the need for a reorganization of the kangaroos' phylogenetic tree. According to a new study by a Senckenberg scientist, published recently in the journal "Scientific Reports," the swamp wallaby is more closely related to the remaining wallaby species and the large red and grey kangaroos and wallaroos than previously assumed. Together with her Australian colleagues from QUT in Brisbane, the researcher was the first to examine the relationships within the kangaroo genus Macropus on the basis of retrotransposons, genes that literally jump across the genetic material.

Like their larger relatives, the kangaroos, the smaller wallabies are an iconic part of the fauna "down under." Even the Australian National Rugby Team is named after them. However, one wallaby stands out among the rest -- the swamp wallaby. It is the only marsupial that is able to switch to "turbo speed" during reproduction, becoming pregnant again before giving birth to the first set of offspring. The animal, which is widespread on the east coast of Australia, also differs from the other wallabies in its appearance, e.g., the shape of its teeth and its more crouched hop.

Until now, the swamp wallaby was placed in its own genus, Wallabia, which only comprises one single species. However, this outsider role is actually not justified -- as recently shown by the molecular-genetic studies at the Senckenberg Biodiversity and Climate Research Centre.

"At the genetic level, the swamp wallaby does not represent a sister genus to the other wallabies, but it belongs to the genus Macropus, like all remaining wallaby species. Thus, it is not only more closely related to the other wallabies than previously thought, but also to Australia's icons, the large red and grey kangaroos and the wallaroos," explains Dr. Maria Nilsson, head of the study.

Of all things, it was retrotransposons -- genes that literally jump across the genetic material -- that shed new light on the relationships among wallabies and kangaroos. These mobile genetic elements are able to make copies of themselves and reinsert these at a different location in the genome. If they occur in the same areas in different species, these species have a common ancestry.

Nilsson elaborates: "Therefore, such jumping genes are also referred to as molecular fossils, which allow inferences on the phylogenetic history. They occur in almost all organisms; due to their properties, they have gained an increasing importance in evolutionary research in recent years."

According to the analysis, the modern subgenera of the kangaroo genus Macropus as well as the swamp wallaby subsequently evolved from a common ancestor approximately five to seven million years ago. During this time period, the forests in Australia began to open up, many later being replaced by spreading grasslands. This habitat was colonized by new species of large red and grey kangaroos and wallaroos. "The wallabies and the swamp wallaby arose at a later date, and they inhabit woodlands," says Nilsson.

Even in this genetic analysis, the swamp wallaby retains a special status. Although it now falls within the genus Macropus, it constitutes a subgenus within it -- and, not surprisingly, this subgenus only consists of one lone species.

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Harmful effects of being overweight underestimated

Weight scale

The harmful effects of being overweight have been underestimated, according to a new study that analysed body mass index (BMI), health and mortality data in around 60,000 parents and their children, to establish how obesity actually influences risk of death. The University of Bristol study is published in the International Journal of Epidemiology (Dec. 1).

Previous studies have suggested that the optimum BMI, at which the risk of death is minimised, appears to be above the range normally recommended by doctors, leading to claims it is good for health to be mildly overweight. However, scientists suspect these studies do not reflect the true effect of BMI on health, because early stages of illness, health-damaging behaviours, such as cigarette smoking, and other factors can lead to both lower BMI and increased risk of death. This makes it difficult to estimate how BMI actually influences risk of death (the causal effect), as opposed to the observed association between BMI and risk of death. This aim of this study was to assess the causal link between BMI and risk of death.

Using HUNT, a Norwegian population-based health cohort study based in a rural county with 130,000 residents, the Bristol Medical School team, with co-workers from the Norwegian University of Science and Technology, were able to see how mortality in the parents related to both their own BMI (the conventional approach) and to the BMI of their adult children. Because BMI of parents and their offspring is related, due to genetic factors, offspring BMI is an indicator of the BMI of the parents. The BMI of adult children is not influenced by illness among the parents, therefore using offspring BMI avoids the problems inherent in simply relating the BMI of the parents to their risk of death.

The health records of around 30,000 mother and child pairs and 30,000 father and child pairs were assessed to examine the extent to which BMI may influence mortality risk in a situation that is not biased by "reverse causation" -- illness leading to low BMI rather than BMI influencing illness.

The team found that when offspring BMI was used instead of the parent's own BMI, the apparent harmful effects of low BMI were reduced and the harmful effects of high BMI were greater than those found in the conventional analyses. Importantly, the results suggest that previous studies have underestimated the harmful effects of being overweight.

The current advice from doctors to maintain a BMI of between 18.5 and 25 is supported by this study, and the widely reported suggestion that being overweight may be healthy is shown to be incorrect.

Dr David Carslake, the study's lead author and Senior Research Associate from the MRC Integrative Epidemiology Unit (IEU) at the University of Bristol, said: "An alarming increase in obesity levels across the world which have risen from 105 million in 1975 to 641 million in 2014, according to a recent Lancet study, create concern about the implications for public health.

"This study demonstrates that correlation is not causation and that when it comes to public health recommendations we need to be cautious interpreting data based on associations alone. We found that previous studies have underestimated the impact of being overweight on mortality and our findings support current advice to maintain a BMI of between 18.5 and 25."

Read more at Science Daily

Rise of ampicillin resistance began years before human use

Low doses of penicillin routinely fed to livestock in the 1950s in North America and Europe may have encouraged antibiotic-resistant bacteria to evolve and spread.

Bacteria that can pass on genes resistant to ampicillin, one of the most commonly used antibiotics today, emerged several years before the widespread use of this antibiotic in humans, according to new research published in The Lancet Infectious Diseases.

Molecular analysis of historical samples of Salmonella by researchers at the Institut Pasteur (Paris, France) suggests that the ampicillin resistance gene (blaTEM-1) emerged in humans in the 1950s, several years before the antibiotic was released onto the pharmaceutical market. The findings also indicate that a possible cause was the common practice of adding low doses of penicillin to animal feed in the 1950s and 60s.

The study comes just weeks after WHO called for the end to routine antibiotic use to promote growth and prevent disease in healthy farm animals.

"Our findings suggest that antibiotic residues in farming environments such as soil, waste water, and manure may have a much greater impact on the spread of resistance than previously thought," says Dr Francois-Xavier Weill, Institut Pasteur, who led the study.

Antibiotic resistance kills around 25,000 people a year in Europe, and this is predicted to rise to over 10 million people worldwide by 2050. Many bacteria that cause serious infections in humans like Salmonella, have already developed resistance to common antibiotics.

Ampicillin, the first broad-spectrum penicillin for the treatment of infections due to Enterobacteria, was released on the market in the UK in 1961. Shortly after (in 1962-1964), the first outbreaks of disease in humans caused by ampicillin-resistant strains of the common zoonotic (which cause disease that can be spread between animals and humans) bacterium, Salmonella enterica var Typhimurium (S. Typhimurium), were identified in the UK.

This short timeline prompted the researchers to investigate the emergence of ampicillin resistance. In this study, they tested 288 historical samples of S. Typhimurium collected from humans, animals, and food and feed in Europe, Asia, Africa, and America between 1911 and 1969. Samples were tested for antibiotic susceptibility and were analysed by whole genome sequencing, in order to identify the mechanisms of resistance to ampicillin.

The researchers found various ampicillin-resistance genes in 11 isolates (3..8%) from human samples. Importantly, the blaTEM-1 gene was found on plasmids (mobile DNA that can be easily copied and transferred between different bacteria) in three isolates taken from humans in France and Tunisia in 1959 and 1960.

The authors note that despite the close proximity between the countries, the vectors of ampicillin resistance (mostly from France) differed from those in the strains responsible for the first outbreaks in the UK in the 1960s. Dr Weill says: "This indicates that the early emergence of ampicillin resistance was due to multiple independent acquisitions of these resistant genes by different bacterial populations and their varying spread across several countries."

"The genetic diversity of these ampicillin-resistant isolates, their resistance mechanisms, and their geographic distribution, indicate that ampicillin resistance had already spread in this prominent zoonotic bacterium in the late 1950s, several years before ampicillin became commercially available."

A report from the UK Central Public Health Laboratory in 1965 raised the idea that low doses of the narrow-spectrum antibiotic penicillin G (also known as benzylpenicillin), routinely added to animal feed, may have contributed to the emergence of ampicillin resistance in humans in the UK (a practice that was banned in the UK in 1969).

In further analyses, the authors confirm that ampicillin resistance genes can be successfully transferred between wild type S. Typhimurium strains after exposure to relatively low levels of penicillin G, similar to those found in the litter of chickens fed with antibiotics in the USA in the 1970s.

The authors note some limitations of this study, particularly the highly selective nature of the available historical isolates that were predominately from France and former French colonies in Africa and Asia.

According to Dr Weill, "Although our study cannot identify a causal link between the use of penicillin G and the emergence of transmissible ampicillin-resistance in livestock, our results suggest that the non-clinical use of penicillins like benzylpenicillin may have encouraged the evolution of resistance genes in the late 1950s. There is an urgent need to re-evaluate the use of antibiotics in animals and for a 'one health' approach to tackling resistance, recognising that bacteria know no borders. This must include close international monitoring and surveillance of resistance in both human and animal health."

Writing in a linked Comment, Dr Sandra Van Puyvelde and colleagues from the Institute of Tropical Medicine Antwerp, Belgium say, "Antibiotic growth promoters have been gradually banned in Europe since 1996 (with a complete ban in 2006), without adverse effects on animal production, but resulting in a decrease in antibiotic resistance in pigs and poultry. Extensive use of antibiotics, however, continues in low-income and middle-income countries and in booming economies, particularly in intense farming such as that of fish and shellfish."

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