爱上海419后花园论坛

The discovery of unknown yeasts hiding in lichens from six continents could shake up a basic idea of what makes up a lichen partnership.

For more than a century, biologists have described a lichen as a fungus growing intimately with some microbes (algae and/or cyanobacteria) that harvest solar energy. The fungus is treated as so important that its name serves as the name for the whole lichen.

Biologists have recognized that more than one fungus can show up in lichen close-ups, but their role hasn’t been clear. Now that may be on the brink of changing.
Fifty-two genera of lichens collected from around the world include a second fungus — single cells, called yeasts, of a previously unknown order now christened Cyphobasidiales. Toby Spribille of the University of Graz in Austria and colleagues report the finding online July 21 in Science.
The first example discovered illustrates why these yeasts might turn out to be more than parasites or mere hitchhikers, says study coauthor John McCutcheon of the University of Montana in Missoula. He and Spribille started the research out of curiosity. They wondered how the yellow, toxin-bearing, thready tangles of lichen called Bryoria tortuosa could have the same fungus and the same algal partner — and thus technically be the same species — as the brown, toxin-poor lichen traditionally called B. fremontii. The researchers looked to see which genes were active in each lichen in hopes that some discrepancy could explain the difference in forms. What the researchers found had nothing to do with the alga or previously known fungus. Instead, ample genetic activity of more abundant yeasts in the toxic B. tortuosa turned out to be the most striking disparity.

After five years of work, the research team now has microscope images of yeast cells embedded in the outer layer, or cortex, of B. tortuosa. Gene-activity results suggest that the yeasts could be what’s making the difference between the forms, maybe even synthesizing toxic vulpinic acid. The yeasts turning up across this widespread class of lichens might explain other mysteries, such as why researchers have largely failed to re-create lichen partnerships in the lab.
It’s a bold hypothesis, but lichenologist Robert Lücking of the Botanic Garden and Botanical Museum Berlin-Dahlem takes the idea of yeast partners seriously. “This will be a huge surprise to the lichenological and mycological community,” he says.

Wolves are having something of an identity crisis. Gray wolves and coyotes might be the only pure wild canine species in North America, a new genetic analysis suggests. Other wolves — like red wolves and eastern wolves — appear to be blends of gray wolf and coyote ancestry instead of their own distinct lineages.

Red wolves contain about 75 percent coyote genes and 25 percent wolf genes, an international team of scientists reports online July 27 in Science Advances. Eastern wolves have about 25 to 50 percent coyote ancestry.
That finding adds another twist to the ongoing battle over wolf protection and regulation in the United States: how to protect a population that’s not its own species but carries valuable genetic information.

Gray wolves used to roam much of North America — until they were hunted to near-extinction. Protection under the Endangered Species Act has helped them to rebound, but their current range is still far smaller than it used to be. Red wolves, found in the southeastern United States, and eastern wolves, found in the Great Lakes region, look similar to gray wolves but are often treated as distinct species. The two groups occupy territory where gray wolves are now scarcer (in the Great Lakes area) or completely gone (in the southeast).

The new study examined the entire genetic makeup, or genome, of 23 wild canines from around North America. The researchers compared the mixed genomes to those from pure coyotes and Eurasian wolves to figure out what percent of each animal’s genetic material came from the wolf and what part came from the coyote.

Red and eastern wolves have historically mated with coyotes, the team found. But gray wolves have recent coyote ancestry too, and neither eastern wolves nor red wolves differ genetically from gray wolves any more than from other individuals of their species. That suggests that these different groups of wolves are more evolutionarily intertwined than previously believed, says Robert Wayne, a biologist at UCLA who coauthored the study

Red wolves and eastern wolves probably arose when gray wolf populations in the eastern United States were hunted by early settlers, says Doug Smith, a biologist who leads the Wolf Restoration Program in Yellowstone National Park. That created room for coyotes to move east, where the struggling wolves bred with them. Mixing genes with coyotes probably helped wolves survive in lean times.
While their coyote genes make red wolves and eastern wolves look slightly different from gray wolves, “we don’t find anything incredibly unique in the red wolf that you can’t find in other canines,” says Bridgett vonHoldt, a biologist at Princeton University who worked with Wayne and collaborators. But they’re still important to protect, because “the wolf part of their genome might actually represent the last of the southeastern gray wolf.” It’s a similar story for the eastern wolf.

Blended species like these are hard to label, Smith says, because traditional species definitions assume clear boundaries that prevent gene sharing.

“Nothing isolates a wolf,” says Smith. “They’re just so capable of moving around.”

Right now, wolves in the United States are managed through a patchwork of federal and state regulations. Red wolves are federally listed as endangered; gray wolves are listed as endangered in some parts of the country, including in the upper Midwest. Genetic mixing makes designing appropriate regulations even more challenging.

“These animals don’t walk around with little name tags on them in the field,” says vonHoldt. “So hybrids or admixed animals don’t always look very different from a pure coyote or pure wolf.”

The only way to ensure that wolf genes stick around in certain areas would be to prohibit killing of both wolves and coyotes, vonHoldt says. But such a restriction would be nearly impossible to implement.

This study is an important step, but its conclusions aren’t definitive, says Paul Wilson, a biologist at Trent University in Ontario, Canada. His work still supports the idea that the eastern wolf is its own species. Comparison with DNA from ancient North American canids — before wolves and coyotes interbred at all — could help further clarify the debate, he says.

Mosquitoes in Miami now appear to be transmitting Zika virus.

Four cases of Zika infection in Florida were probably acquired via the bite of local mosquitoes, the state’s health department announced July 29. These are the first cases of local transmission of the virus in the continental United States.

“Zika is now here,” Tom Frieden, director of U.S. Centers for Disease Control and Prevention, said in a news briefing July 29.

No mosquitoes trapped yet have tested positive for the virus, but officials suspect Aedes aegypti mosquitoes in a several-block area in north Miami are to blame. “Everything we’ve seen so far indicates that this is mosquito-borne transmission,” Frieden said.

Florida’s small cluster of cases does not necessarily foreshadow an epidemic, he said. The four infected people probably were bitten in early July. Since then, Florida has stepped up efforts to stamp out mosquitoes — including going door-to-door to get rid of standing water and spraying insecticides by truck and by people on foot.

“We believe that widespread transmission in the continental U.S. is unlikely,” Frieden said. “But it’s not impossible.”

Two other mosquito-borne diseases, dengue and chikungunya, have spread locally in Florida in the past. But, Frieden said, those diseases generally dead-end after infecting just one person.

From 1863 to 1890, Leopold and Rudolf Blaschka made more than 10,000 sea creatures out of glass. There were anemones with tapered tentacles and pearled undersides, translucent jellyfish trailing the most delicate threads and feather stars more than worthy of their name despite their rigid composition. The intricate invertebrates, crafted by the father-son team at their studio in Dresden, Germany, were shipped across the world to serve as teaching models at universities and museums. In an era before marine surveys and underwater photography, before the rise of scuba diving resorts, the Blaschkas showed the world the wonders of the sea.

Over five dozen of their glass wonders are now on display at the Corning Museum of Glass in “Fragile Legacy.” Though the exhibit opens with glass eyeballs and a piece of jewelry — a nod to the Blaschkas’ pre-invertebrate business — the highlight is a darkened room set up like an aquarium, with sea creatures seemingly floating in blue. There’s a notable absence of museum placards and descriptions. “We really want people to look at the glassiness,” says Marvin Bolt, a curator of the exhibit, before pointing out the “Field Guide to Underwater Models.” The pamphlet contains each animal’s species name, as it was known in 1885 (when Cornell University acquired the pieces, now on loan to Corning) and as it is known today.
The aquarium offers a sense of the Blaschkas’ style, but it’s the room next door that provides the substance. Sketches and watercolors, bottles of colored powders, tweezers, pliers, scoops and wire, along with a demonstration video, give a fuller sense of how the Blaschkas did their work. Equally impressive are the matchboxes filled with kleine augen (“little eyes” in German) and other tiny but uniform component pieces, suggestive of an assembly line approach to handcrafting the final glass forms. A series of case studies explains how conservators stabilized the pieces, and a trailer for a related documentary, also titled Fragile Legacy, highlights the vulnerability, not of the glass, but of the real-world creatures living in warming seas.
There’s one thing you won’t find in this exhibit — the flowers that the Blaschkas are most famous for today, commissioned by Harvard beginning in 1886. But you’ll spot seeds of this later work in the sea animals’ slender stalks and garlands of orbs. As the Blaschkas moved on to new subjects, their artistry evolved from the forms they’d already mastered.

What had two puny arms, lived 90 million years ago and probably chowed down on other dinosaurs? (Hint: It’s not T. rex.)

A new dinosaur discovered in what is now Patagonia had the runty forelimbs of a Tyrannosaurus rex but is no cousin of the giant iconic predator, researchers report July 13 in PLOS ONE.

The new species, Gualicho shinyae, has a close relative in Africa, an analysis of fossils suggests. T. rex’s ancestors, on the other hand, came from Asia.
Gualicho is a “smaller, slimmer, trimmer version of a T. rex,” says study coauthor Peter Makovicky, a paleontologist at the Field Museum in Chicago. It probably weighed about a ton and was longer than a pickup truck.
In 2007, Makovicky’s team discovered Gualicho’s partial skeleton — including those impractical arms. The dinosaur probably caught prey with its huge head, Makovicky says. Though the researchers haven’t dug up a skull yet, tiny arms seem to be a trade-off for a big head. Finding Gualicho’s skull would help nail down that idea, he adds.

Gualicho may have fed on grazers called ornithopods, such as duck-billed dinosaurs. Or perhaps it fed on the long-necked, long-tailed sauropods, which were common in the region. But only the youngsters. Sauropod adults were gigantic, Makovicky says, definitely not prey for a (relatively) little guy like Gualicho.

It’s hard to pin down Stephen Wolfram’s scientific discipline. He is part mathematician, part computer scientist, part physicist. He’s also an inventor and entrepreneur, known for the mathematics software package Mathematica and a variety of other endeavors. And he blogs.

Among his blog posts and other essays and talks are commentaries on the lives of other prominent figures from science and math; some Wolfram knew personally, others he has researched extensively. In his new book Idea Makers, Wolfram has collected accounts of 16 such people, discussing their work and its meaning for the nature of science and the process of understanding math, computing and the physical world. Each entry provides a healthy dose of personal information as well.
Some of the people Wolfram discusses are widely known — Richard Feynman and Steve Jobs, for example. Others are relatively obscure, such as Russell Towle and Richard Crandall. But all have captivated Wolfram’s interest, either by way of friendship or their historical importance for the fields of study that Wolfram himself has contributed to.

On the historical side, Wolfram offers his views of the logician Kurt Gödel, computer scientist (perhaps the original computer scientist) Alan Turing and mathematicians John von Neumann and George Boole. Wolfram provides an especially extensive discussion of Ada Lovelace and her interactions with Charles Babbage as they contemplated the prospect of powerful computing engines a century ahead of their time.

Wolfram also dives into the story of Srinivasa Ramanujan, and the lessons his genius offers about the nature of math. With little formal training, Ramanujan discovered many surprising results that seemed at first glance to be a bunch of “random facts of mathematics.” But in recent decades, many have been linked to deep mathematical principles that he seems to have somehow perceived without knowing it. How did he do it? Wolfram suspects that he “had intuition and aesthetic criteria that in some sense captured some of the deeper principles we now know, even if he couldn’t express them directly.”

Personal style, whether as reflected in the subtle genius of Ramanujan or the boldness of vision-driven Jobs, plays an underappreciated role in the progress of science and technology. Wolfram has collected some illuminating examples of the ways the human side of scientific thinkers can enrich the work they do.

Zika may harm grown-up brains.

The virus, which can cause brain damage in infants infected in the womb, kills stem cells and stunts their numbers in the brains of adult mice, researchers report August 18 in Cell Stem Cell. Though scientists have considered Zika primarily a threat to unborn babies, the new findings suggest that the virus may cause unknown — and potentially long-term — damage to adults as well.

In adults, Zika has been linked to Guillain-Barré syndrome, a rare neurological disorder (SN: 4/2/16, p. 29). But for most people, infection is typically mild: a headache, fever and rash lasting up to a week, or no symptoms at all. In pregnant women, though, the virus can lodge in the brain of a fetus and kill off newly developing cells (SN: 4/13/16).
If Zika targets newborn brain cells, adults may be at risk, too, reasoned neuroscientist Joseph Gleeson of Rockefeller University in New York City and colleagues. Parts of the forebrain and the hippocampus, which plays a crucial role in learning and memory, continue to generate nerve cells in adult brains.

In mice infected with Zika, the virus hit these brain regions hard. Nerve cells died and the regions generated one-fifth to one-half as many new cells compared with those of uninfected mice. The results might not translate to humans; the mice were genetically engineered to have weak immune systems, making them susceptible to Zika.

But Zika could potentially harm immunocompromised people and perhaps even healthy people in a similar way, the authors write.

A blood cancer uses a secret weapon for tearing bone apart. That same mechanism may allow breast cancer and other types of tumors to spread to bones, a new study suggests.

In patients with the blood cancer multiple myeloma, an enzyme called thymidine phosphorylase sets off a chain reaction that leads to bone destruction, researchers report August 24 in Science Translational Medicine. Drugs that inhibit the enzyme caused mice to lose less bone.

The findings may lead to new therapies for stopping bone loss from multiple myeloma or other cancers that spread to bone. Halting bone destruction may even make bones less hospitable for tumors, stopping their growth, too, says Jing Yang, a cancer researcher at the University of Texas MD Anderson Cancer Center in Houston.
Multiple myeloma is a cancer that grows in bone marrow. Myeloma cells talk directly to bone-remodeling cells. The tumor cells’ messages send bone-building cells on permanent vacation while stimulating bone-demolishing cells. The result is weak bones, holes, fractures and bone pain.

Yang and colleagues had previously discovered that a biological process in myeloma cells that weakens bones also boosts production of thymidine phosphorylase. The enzyme was known to be more abundant in many types of cancers where it stimulates blood vessel growth to tumors and stops tumor cells from dying. No one knew it was involved in poking holes in bones.

Thymidine phosphorylase in myeloma cells kicks off a series of steps that convert a building block of DNA called thymidine into a small molecule called 2-deoxy-D-ribose, or 2DDR. Myeloma cells secrete 2DDR and bone cells pick it up, sending a signal to turn off genes that control bone cell activity. When bone-building cells called osteoblasts get the message, they stop working, Yang and colleagues discovered. But bone-eating cells called osteoclasts work harder. That tips the cycle of bone remodeling toward destruction.

Yang’s team injected myeloma cells into the femurs of mice. After the cancer was established, the researchers treated some of the mice with drugs that inhibit thymidine phosphorylase. Those mice lost less bone than untreated mice with myeloma did.

The drugs have already been approved for treating other types of cancer. If the results of the mouse study hold up in human clinical tests, the drugs may also preserve bone in myeloma patients and people with other cancers that have spread to their bones, Yang says. She hopes that the drugs may even help repair bone damage.
“We’re getting better at getting rid of myeloma cells,” says Rebecca Silbermann, a hematologist at Indiana University School of Medicine in Indianapolis. “But we have no way to heal those bone lesions at this point, even if a person’s myeloma is gone.”

Currently, drugs used to maintain bone strength slow bone-dissolving cells, but don’t put bone-building cells back to work, Silbermann says. Drugs like the thymidine phosphorylation inhibitors used in the study might have better results because they may prod bone-building cells to do their jobs again.

Because thymidine phosphorylase’s message passes through multiple receivers and transmitters, researchers also have multiple options for interrupting the relay, says Yibin Kang. That interference may one day allow doctors to stop or even reverse bone loss from cancer and maybe even from osteoporosis, says Kang, a cancer researcher at Princeton University who studies how breast cancer spreads to bone.

While the study provides important new clues about how myeloma breaks down bone, it’s not clear whether thymidine phosphorylase starts the process early in cancer or just helps perpetuate it later, says Qing Yi, a myeloma researcher at the Cleveland Clinic. It’s also too early to tell whether breast cancer and others use the same process for breaking down bone, he says. “This has a long way to go before it can ever reach the patient.”

A melting snow patch in Greenland has revealed what could be the oldest fossilized evidence of life on Earth. The 3.7-billion-year-old structures may help scientists retrace the rise of the first organisms relatively soon after Earth’s formation around 4.5 billion years ago (SN: 2/8/14, p. 16), the discoverers report online August 31 in Nature.

Unlike dinosaur bones, the new fossils are not preserved bits of an ancient critter. The Greenland fossils are mounds of minerals a few centimeters tall that may have been deposited by clusters of microbes several hundred million years after Earth formed. The shape and chemical composition of the mounds, called stromatolites, match those formed by modern bacterial communities living in shallow seawater, says a team led by geologist Allen Nutman of the University of Wollongong in Australia.

If confirmed, the fossils demonstrate that sophisticated, mound-building microbial life appeared early on in Earth’s history. That early start backs up previous genetic and chemical studies that place the advent of basic life on Earth before 4 billion years ago (SN Online: 10/19/15).

Hawaiian honeycreepers are a marvel of evolution. Millions of years ago, some finches arrived on the Hawaiian Islands and began to diversify. As the Pacific Plate moved over the Hawaiian hotspot and new islands formed and others shriveled away, these colorful songbirds evolved into more than 50 species that differed so much in what they ate, where they lived and how they looked that it took scientists quite a while to figure out that they were all related.

More than half of those species are now gone. “Many extinctions took place when the islands were first settled by Polynesian people,” notes Helen James, who, as curator of birds at Smithsonian’s National Museum of Natural History, has studied the birds’ evolutionary history. Then Westerners arrived and bird populations started to disappear more quickly due to a combination of threats, including habitat loss, introduction of invasive species and the arrival of diseases such as avian malaria.

Bird populations on Hawaii’s oldest island, Kauai, have been hit especially hard. Kauai lost at least eight species of honeycreepers — as well as several other “marvelous species” of birds, James notes — before people began keeping good records of the island’s fauna. And now a new study warns that the birds’ situation will get worse — and soon. The honeycreepers that are left on the island are declining fast, and some species could disappear in as little as a decade.

Eben Paxton of the U.S. Geological Survey Pacific Islands Ecosystems Research Center at Hawaii Volcanoes National Park and colleagues looked at population trends for seven species of native forest birds living on Kauai’s Alakai Plateau, the eroded crater of a long-extinct volcano. On other Hawaiian islands, only high-elevation areas have generally been cool enough to keep out the mosquitoes that spread avian diseases. But on lower-lying Kauai, its forests have tended to be cooler than similar-elevation regions on the other islands, so spots such as the Alakai Plateau have been disease-free refuges for native birds.
Or, they were. A 2014 study found that disease prevalence in birds had more than doubled there between 1994-1997 and 2007-2013. Climate change had warmed the plateau enough that disease-laden mosquitoes could spread.
In the new study, Paxton and his colleagues found that six of seven native forest birds surveyed (an eighth proved too wily for scientists to accurately count) are rapidly disappearing and their ranges contracting. All six are honeycreepers, and four are now found only in small, remote parts of the plateau. Fewer than 1,000 Akekee and fewer than 500 Akikiki remain, the team reports September 2 in Science Advances.

“If native species linearly decline at a rate similar to or greater than that of the past decade, then multiple extinctions are likely in the next decade,” the team writes.

James says that she hopes the new findings will be a call to action. “Their data show alarming declines in population and geographic ranges of endemic Hawaiian honeycreepers on the island of Kauai,” she says. The birds’ extinction “would be a tremendous loss.”

Even without avian diseases and climate change, the honeycreepers still face threats from habitat loss, introduced predators and competition with non-native birds (some of whom, such as the Japanese bush-warbler, are thriving on the plateau, the study finds). Reducing those threats could buy the honeycreepers some time to adapt to the growing threat of disease. Scientists can also help by developing genetically modified mosquitoes and figuring out why honeycreepers are so susceptible to avian malaria — and how to protect them from it, James notes.

“The Hawaiian honeycreepers are a classic example of adaptive radiation in animals, second only to Darwin’s finches,” she says. Losing Kauai’s endemic honeycreepers “would definitely cost us in terms of our opportunities to study, understand and appreciate nature.”