Did Exploding Stars Help Life On Earth to Thrive?

Research by a Danish physicist suggests that the explosion of massive stars -- supernovae -- near the Solar System has strongly influenced the development of life. Prof. Henrik Svensmark of the Technical University of Denmark (DTU) sets out his novel work in a paper in the journal Monthly Notices of the Royal Astronomical Society.

When the most massive stars exhaust their available fuel and reach the end of their lives, they explode as supernovae, tremendously powerful explosions that are briefly brighter than an entire galaxy of normal stars. The remnants of these dramatic events also release vast numbers of high-energy charged particles known as galactic cosmic rays (GCR). If a supernova is close enough to the Solar System, the enhanced GCR levels can have a direct impact on the atmosphere of Earth.

Prof. Svensmark looked back through 500 million years of geological and astronomical data and considered the proximity of the Sun to supernovae as it moves around our Galaxy, the Milky Way. In particular, when the Sun is passing through the spiral arms of the Milky Way, it encounters newly forming clusters of stars. These so-called open clusters, which disperse over time, have a range of ages and sizes and will have started with a small proportion of stars massive enough to explode as supernovae. From the data on open clusters, Prof. Svensmark was able to deduce how the rate at which supernovae exploded near the Solar System varied over time.

Comparing this with the geological record, he found that the changing frequency of nearby supernovae seems to have strongly shaped the conditions for life on Earth. Whenever the Sun and its planets have visited regions of enhanced star formation in the Milky Way Galaxy, where exploding stars are most common, life has prospered. Prof. Svensmark remarks in the paper, "The biosphere seems to contain a reflection of the sky, in that the evolution of life mirrors the evolution of the Galaxy."

In the new work, the diversity of life over the last 500 million years seems remarkably well explained by tectonics affecting the sea-level together with variations in the supernova rate, and virtually nothing else. To obtain this result on the variety of life, or biodiversity, he followed the changing fortunes of the best-recorded fossils. These are from invertebrate animals in the sea, such as shrimps and octopuses, or the extinct trilobites and ammonites.

They tended to be richest in their variety when continents were drifting apart and sea levels were high and less varied when the land masses gathered 250 million years ago into the supercontinent called Pangaea and the sea-level was lower. But this geophysical effect was not the whole story. When it is removed from the record of biodiversity, what remains corresponds closely to the changing rate of nearby stellar explosions, with the variety of life being greatest when supernovae are plentiful. A likely reason, according to Prof. Svensmark, is that the cold climate associated with high supernova rates brings a greater variety of habitats between polar and equatorial regions, while the associated stresses of life prevent the ecosystems becoming too set in their ways.

He also notices that most geological periods seem to begin and end with either an upturn or a downturn in the supernova rate. The changes in typical species that define a period, in the transition from one to the next, could then be the result of a major change in the astrophysical environment.

Life's prosperity, or global bioproductivity, can be tracked by the amount of carbon dioxide in the air at various times in the past as set out in the geological record. When supernova rates were high, carbon dioxide was scarce, suggesting that flourishing microbial and plant life in the oceans consumed it greedily to grow. Support for this idea comes from the fact that microbes and plants dislike carbon dioxide molecules that contain a heavy form of carbon atom, carbon-13. As a result, the ocean water is left enriched by carbon-13. The geological evidence shows high carbon-13 when supernovae were commonest -- again pointing to high productivity. As to why this should be, Prof. Svensmark notes that growth is limited by available nutrients, especially phosphorus and nitrogen, and that cold conditions favour the recycling of the nutrients by vigorously mixing the oceans.

Although the new analysis suggests, perhaps surprisingly, that supernovae are on the whole good for life, high supernova rates can bring the cold and changeable climate of prolonged glacial episodes. And they can have nasty shocks in store. Geoscientists have long been puzzled by many relatively brief falls in sea-level by 25 metres or more that show up in seismic soundings as eroded beaches. Prof. Svensmark finds that they are what can be expected when chilling due to very close supernovae causes short-lived glacial episodes. With frozen water temporarily bottled up on land, the sea-level drops.

Read more at Science Daily

Why We're Drawn to Fire

As America's $2 billion candle industry attests, there is something mesmerizing about a flickering flame. Most people love to feel fire's warmth, to test its limits, and to watch the way it consumes fuel. When there's a candle or bonfire around, why can't we help staring?

A dancing fire is pretty, as well as tantalizingly dangerous, but there may be a much deeper reason for our attraction to it. Daniel Fessler, an evolutionary anthropologist at the University of California, Los Angeles, has conducted research that indicates an adult's fascination with fire is a direct consequence of not having mastered it as a child. Fire has been crucial to human survival for around one million years, and in that time, Fessler argues, humans have evolved psychological mechanisms specifically dedicated to controlling it. But because most Westerners no longer learn how to start, maintain and use fire during childhood, we instead wind up with a curious attraction to it -- a burning desire left to languish.

"My preliminary findings indicate that humans are not universally fascinated by fire," Fessler told Life's Little Mysteries. "On the contrary, this fascination is a consequence of inadequate experience with fire during development."

In societies where fire is traditionally used daily as a tool, Fessler has found that children are only interested by fire until such point as they attain mastery of it. After that point -- usually at age 7 -- people display little interest in fire and merely use it as one would use any ordinary tool. "Hence, the modern Western fascination with fire may reflect the unnatural prolongation into adulthood of a motivational system that normally serves to spur children to master an important skill during maturation," Fessler wrote in an email.

Unlike a spider that inherently knows how to weave a web, humans don't instinctively know how to produce and control fire. The ability must be learned during childhood. This may be because there was no universal method of fire building and control among our ancestors, who lived in diverse environments, and so there was no single method for evolution to ingrain in us. Instead, "fire learning" became the instinct. As Fessler put it in an article in the Journal of Cognition and Culture, "The only avenue open to selection processes operating on a species as wide-ranging as ourselves was to rely on learning for the acquisition of the requisite behaviors."

Children are universally fascinated by predatory animals in a similar manner in which they are fascinated by fire. Because both could seriously harm or kill them, evolution requires that they be interested in those subjects, Fessler argues, as a way of ensuring that they pay special attention to information obtained about them. For example, children are naturally curious about which animals are dangerous and which aren't, as well as which materials are flammable and which aren't, and what the consequences are of adding, removing and rearranging objects in a fire. Our brains soak up this predator and fire knowledge.

In the United States, children's natural inclination to learn about fire is evidenced by the hundreds of deaths that occur each year due to "fire play," or the deliberate setting of a fire for no purpose beyond the fire itself. A study by the psychiatrist David Kolko of the University of Pittsburgh found that about three-quarters of children set a play fire during the three-year window of the study (1999-2001). Prior studies found that curiosity was the primary motive for the behavior, which, fire department records show, peaks at age 12.

Read more at Discovery News

Are Pet Psychics Real?

We can all name at least a handful of fictional characters who can communicate with animals: Tarzan, Aquaman, the Horse Whisperer (a character appearing in a Nichols Evans novel and Robert Redford film), Dr. Doolittle and others.

Of course, most people communicate with animals all the time; pet lovers are famous for cooing baby talk to their animals and repeatedly asking banal, rhetorical questions like, "Do you want some food?" or "Who's a good boy? Who's a good boy?"

But pet psychics claim to do something more remarkable: They speak to animals and get information back. This is done, they say, by some sort of interspecies psychic power or telepathy.

Of course, psychic communication between humans has never been scientifically proven, so claims of psychic communication between animals and humans begins on very shaky ground. At least humans can share a common language; how a psychic could possibly translate the thoughts and intentions of a parakeet, fish, hamster, horse, spider or any other animal into human language is a mystery.

Yet thousands of people in real life claim to have exactly such a remarkable ability. For example, a Canadian woman named Lauren Bode claims she's a real-life horse whisperer.

Bode says that several horses at Toronto's Far Enough Farm telepathically told her that they are upset about plans to move them from their current location to another farm nearby. They are anxious about the June 30 move and worried about whether they will like their new home.

Bode did not explain how exactly the horses told her this, nor how they got wind of the news about the planned relocation; perhaps they learned enough English to eavesdrop on their trainers' conversations. If so, it would not be the first time that a horse was able to fool humans into believing it could understand languages.

Human-Animal Communication

A 2008 poll found that 67 percent of pet owners say they understand their animals' purrs, barks and other noises, and 62 percent said that when they speak, their pet understands them (or at least their intent).

One in five owners claim that they and their pets understand each other completely. One-quarter of cat owners said they completely understood their pets' sounds, while only 16 percent of dog owners said they were fluent in barks. This is not necessarily psychic power, but intuition, guessing and common sense.

Even something as simple as tone of voice carries a huge amount of information about intent; sharp, loud phrases like "Stop!" convey a clearly different meaning than a smooth, sing-song phrase like, "Hey buddy!"

Most animals (including humans) pick up plenty of accurate nonverbal cues about each other's intents. And, of course, just because pet owners (or psychics) think they communicate great with their pets doesn't mean that the other party feels the same way; just ask any couple.

Testing Pet Psychics

One major problem with trying to prove pet psychic abilities is that usually there's no way to know if the information they give is accurate or not. For example, if a concerned pet owner consults a psychic about her kitty's unusual behavior and is told that her cat says he's acting out because he doesn't like the color of the new drapes in the living room, or a neighbor dog looked at him menacingly, or he senses tension in the marriage, who's to say the psychic is wrong? The psychic could be misunderstanding the cat's messages -- or even making it all up -- and there's no way to prove otherwise.

Read more at Discovery News

Minivan-sized Asteroid Exploded Over California

The source of loud "booms" accompanied by a bright object traveling through the skies of Nevada and California on Sunday morning has been confirmed: It was a meteor. A big one.

It is thought to have been a small asteroid that slammed into the atmosphere at a speed of 15 kilometers per second (33,500 mph), turning into a fireball, and delivering an energy of 3.8 kilotons of TNT as it broke up over California's Sierra Nevada mountains. Bill Cooke, head of NASA's Meteoroid Environment Office, classified it as a "big event."

"I am not saying there was a 3.8 kiloton explosion on the ground in California," Cooke told Spaceweather.com. "I am saying that the meteor possessed this amount of energy before it broke apart in the atmosphere. (The map) shows the location of the atmospheric breakup, not impact with the ground."

Cooke went on to say that the meteor likely penetrated very deep into the atmosphere, producing the powerful sonic booms that rattled homes across the region. According to Reuters, car alarms in Carson City, Nev., were even triggered.

After some rough calculations, Cooke has been able to estimate the mass of the incoming object -- around 70 metric tons. This was a fairly hefty piece of space rock. From this estimate he was also able to arrive at an approximate size of the meteor: "Hazarding a further guess at the density of 3 grams per cubic centimeter (solid rock), I calculate a size of about 3-4 meters, or about the size of a minivan."

Although there were numerous reports of sightings in Nevada and California, there was few immediate clues as to where the fireball ended its journey. But with the help of two infrasound stations, the source of the explosion could be resolved.

"Elizabeth Silber at Western University has searched for infrasound signals from the explosion," said Cooke. "Infrasound is very low frequency sound which can travel great distances. There were strong signals at 2 stations, enabling a triangulation of the energy source at 37.6N, 120.5W. This is marked by a yellow flag in the map (above)."

Interestingly, the estimated size of the California fireball is bigger than the small 3-meter-wide asteroid that exploded over Sudan in 2008. That one delivered an energy of 1.1–2.1 kilotons of TNT. Asteroid 2008 TC3 was actually the first-ever space rock to be detected before it hit the Earth's atmosphere. With astonishing accuracy, astronomers at Mount Lemmon telescope in Arizona managed to spot the tiny asteroid and infrasound stations in Kenya triangulated the location where the asteroid hit. Using this information, meteorite hunters were able to recover fragments of the impact.

Read more at Discovery News

The Search Is On For Elusive White Whale

A team of Russian scientists say they will embark on a quest next week to observe the only all-white, adult killer whale ever spotted -- a majestic and elusive bull they have named Iceberg.

The researchers from the universities of Moscow and Saint Petersburg first spotted the orca's towering, two-metre (about six feet) dorsal fin break the surface near the Commander Islands in the North Pacific in August 2010.

Living in a pod with 12 other family members, Iceberg was deemed to be at least 16 years old, given the size of his dorsal fin, said Erich Hoyt, co-director of the Far East Russia Orca Project (FEROP).

"This is the first time we have ever seen an all-white, mature male orca," Hoyt told AFP. "It is a breathtakingly beautiful animal."

The scientists decided to hold back on releasing photographs of Iceberg until they were able to study him further, "but we have been looking for him ever since," said Hoyt.

Orcas can travel thousands of miles.

The scientists would like to establish whether Iceberg is albino -- a genetic condition that leaves animals unable to produce melanin, a dark pigment of skin, hair and the eye's retina and iris.

Many albino animals never grow into adulthood. Their visibility is a disadvantage in the hunt for food and protection against predators.

Two other white orcas are known to live in the waters where Iceberg was spotted, east of Kamtchatka peninsula in Russia's far-east, but they are juveniles.

Read more at Discovery News

Costs of 'Dirty Bomb' Attack in Los Angeles

A dirty bomb attack centered on downtown Los Angeles' financial district could severely impact the region's economy to the tune of nearly $16 billion, fueled primarily by psychological effects that could persist for a decade.

The study, published by a team of internationally recognized economists and decision scientists in the current issue of Risk Analysis, monetized the effects of fear and risk perception and incorporated them into a state-of-the-art macroeconomic model.

"We decided to study a terrorist attack on Los Angeles not to scare people, but to alert policymakers just how large the impact of the public's reaction might be," said study co-author William Burns, a research scientist at Decision Research in Eugene, Ore. "This underscores the importance of risk communication before and after a major disaster to reduce economic losses."

Economists most often focus on the immediate economic costs of a terrorist event, such as injuries, cleanup and business closures. In this scenario, those initial costs would total just over $1 billion.

"Terrorism can have a much larger impact than first believed," said study co-author Adam Rose, a research professor with the USC Price School of Public Policy and USC's Center for Risk and Economic Analysis of Terrorism Events (CREATE). "The economic effects of the public's change in behavior are 15 times more costly than the immediate damage in the wake of a disaster."

"These findings illustrate that because the costs of modern disasters are so large, even small changes in public perception and behaviors may significantly affect the economic impact," said Rose, who has published economic estimates of the 9/11 attacks, the Northridge Earthquake and other major disasters.

To estimate how fear and risk perception ripple through the economy after a major terrorist event, the researchers surveyed 625 people nationwide after showing them a mock newspaper article and newscasts about the hypothetical dirty bomb attack to gauge the public's reticence to return to normal life in the financial district.

The study translated these survey results into estimates of what economic premiums would be put on wages and what discounts shoppers would likely require in the aftermath of a terrorist attack.

After six months, 41 percent of those surveyed said they would still not consider shopping or dining in the financial district. And, on average, employees would demand a 25 percent increase in wages to return to their jobs.

"The stigma generated by dirty bomb radiation could generate large changes in the perceived risk of doing business in the region," said co-author James Giesecke of the Centre of Policy Studies at Monash University. "However, with regional economies in competition with one another for customers, businesses, and employees, it takes only small changes in perceived risk to generate big losses in economic activity."

The paper relied on one of 15 planning scenarios -- the detonation of a dirty bomb in a city center -- identified by the Department of Homeland Security in an effort to focus anti-terrorism spending nationwide.

Read more at Science Daily

Marco Polo Really Did Go To China, Maybe

A meticulous description of currency and salt production could restore Marco Polo's honor by proving  that he really did go to China, a new study into the explorer's accounts of the Far East suggests.

"Polo was not a swindler," said Hans Ulrich Vogel, Professor of Chinese Studies at the German University of Tübingen.

Vogel reexamines the great Venetian traveler in a new book entitled "Marco Polo Was in China."

"The strongest evidence is that he provided complex and detailed information about monetary conditions, salt production, public revenues and administrative geography which have been overlooked so far, but are fully corroborated in Chinese sources," Vogel told Discovery News.

The historian noted that these Chinese sources were collated or translated long after Marco Polo’s time.

"So he could not have drawn on them. He could not even read Chinese," he said.

Although there is no doubt Polo existed -- traces of his family home are still around in Venice -- many have questioned whether the 13th-century traveler actually made it to China.

Skeptics argue that his famous travelogue Description of the World, commonly called The Travels of Marco Polo, does not mention several distinctive features of the Chinese society.

Born around 1254 in the Venetian Republic, Polo claimed that he reached China with his merchant father and uncle in 1275, at age 17. He would spend the next 24 years venturing into the Far East China, serving for some years in the court of Mongol emperor Kublai Khan.

The story of the explorer's return to Venice in 1295 and of the subsequent coup de theater when he threw back his Tartar clothes and allowed precious stones to cascade over the floor, has become part of the Polo legend.

Since the mid-eighteenth century, doubts have been raised about Marco Polo’s presence in China.

Historian Frances Wood argued in her 1995 book "Did Marco Polo Go to China?" that the famous explorer didn't even get beyond Constantinople. He would have made the rest of the trip up, with the help of an imaginative ghostwriter, Rustichello da Pisa, cobbling together details provided by fellow traders who had actually been there.

Although Polo's tales of exotic lands inspired Columbus and became the model for generations of explorers, scholars wondered why he did not mention tea, chopsticks, the Chinese writing system, and the practice of binding women's feet.

Furthermore, there is no mention of the Great Wall, while Marco, his father and his uncle are not recorded in any Chinese document.

According to Vogel, skeptics have often overestimated the frequency of documentation and the intentions of Chinese historiographers.

"Even Giovanni de Marignolli (1290-1357), an important papal envoy at the court of the Yuan rulers, is not mentioned in any Chinese sources – nor his 32-man retinue, nor the name of the pope," he said.

As for the Great Wall, new research has established that it did not exist at the time.

"The original wall had long since disintegrated, while the present structure -- a product of the Ming Dynasty (1368-1644) -- was yet to be erected," said Vogel.

Other historians have used these arguments to rehabilitate the Venetian traveler, but Vogel used new data, focusing on a largely neglected part of Polo's travelogue.

"He is the only one to describe precisely how paper for money was made from the bark of the mulberry tree. Not only he detailed the shape and size of the paper, he also described the use of seals and the various denominations of paper money," said Vogel.

According to the historian, Polo's Travels is not a 13th century guidebook to China - on the contrary, it's a rather dry manual to the commerce of the Silk Road.

"Marco Polo reported on the monopolizing of gold, silver, pearls and gems by the state – which enforced a compulsory exchange for paper money," said Vogel.

"He described the punishment for counterfeiters, as well as the 3% exchange fee for worn-out notes and the widespread use of paper money in official and private transactions," he added.

Vogel noted that Polo is also the only one among his contemporaries to explain that paper money was not in circulation in all parts of China, but was used primarily in the north and in the regions along the Yangtze.

According to Polo, cowries, salt, gold and silver were the main currencies in other parts of China such as Fujian and Yunnan.

"This information is confirmed by archaeological evidence and Chinese sources compiled long after Polo had written his Travels," Vogel said.

The Venetian traveler's description of salt production was also accurate and unique. Not only he listed the most important salt production centers, but described the methods used to make salt and detailed the value of salt production.

Read more at Discovery News

New Purple Crab Species Found in Philippines

Four new species of freshwater crab, bright purple in color, have been discovered in the biologically diverse but ecologically-threatened Philippines, the man who found them said Saturday.

The tiny crustaceans burrow under boulders and roots in streams, feeding on dead plants, fruits, carrion and small animals in the water at night, said Hendrik Freitag of Germany's Senckenberg Museum of Zoology.

Found only in small, lowland-forest ecosystems in the Palawan island group, most have purple shells, with claws and legs tipped red.

"It is known that crabs can discriminate colors. Therefore, it seems likely that the coloration has a signal function for the social behavior, e.g. mating," Freitag told AFP by email on Saturday.

"This could explain why large males of various Insulamon species are more reddish compared to the generally violet females and immature males."

Scientists began extensive investigations of similar freshwater crabs in the area in the late 1980s, when one new species was found -- the Insulamon unicorn, Freitag said.

More field work led Freitag to conclude there were four other unique species.

"Based on available new material, a total of five species are recognized... four of which are new to science," Freitag wrote in the latest edition of the National University of Singapore's Raffles Bulletin of Zoology.

The carapace of the biggest, Insulamon magnum, is just 53 millimeters by 41.8 millimeters while the smallest, Insulamon porculum, measures 33.1 by 25.1 millimeters.

The two other new species were called Insulamon palawense and Insulamon johannchristiani.

The four slightly differ from the first find, and from each other, in the shapes of their body shells, legs, and sex organs.

US-based Conservation International lists the Philippines as one of 17 countries that harbors most of Earth's plant and animal life.

Read more at Discovery News

Eternal Life? Nobel Laureate Rita Levi Montalcini Turns 103

Has Dr. Rita Levi Montalcini unlocked the secret of eternal life? The oldest living and the longest-lived Nobel laureate in history, Montalcini celebrates today her 103th birthday.

"I can say my mental capacity is greater today than when I was 20, since it has been enriched by so many experiences," she says.

Her longevity might be the result of an unusual potion she takes every day in the form of eye drops -- a dose of nerve growth factor (NGF), which she discovered (jointly with American co-worker Stanley Cohen), in June 1951 in the labs of Washington University in St. Louis.

A protein essential for the growth, maintenance and survival of sensory and sympathetic neurons (nerve cells) in the peripheral nervous system, NGF was not widely recognized until 1986, when it won Levi-Montalcini and Cohen the Nobel Prize in Physiology or Medicine.

Levi-Montalcini still follows the developments of her findings at the European Brain Research Institute, which she founded in Rome.

Indeed, her work has had a significant influence on research exploring several diseases, including cancer, Parkinson's disease and Alzheimer's disease.

Rita, as she prefers to be called, celebrated her birthday privately, raising a toast with some of her closest collaborators.

As always, she was exquisitely dressed and wore some ancient jewels, the Italian daily Affari Italiani writes.

In line with her motto "I look forward," she decided to wait for the cake until this fall.

"She will celebrate at the Brain Forum in Rome, which is dedicated to her amazing career," the daily wrote.

"Grazie! Thank you," Levi-Montalcini wrote on her Facebook page, in response to innumerable birthday wishes.

Envisaging a quantum Internet, for now she is pleased to find out that her Facebook likes grew "from 2,000 to 200,000."

She now continues to work as a senator for life, and last month harshly criticized Mario Monti's government of technocrats for abolishing the peer review mechanism in funding policies to researchers.

"Italy -- and quite possibly the world -- has never seen a scientist quite like her," the journal Nature wrote on the occasion of her widely celebrated 100th birthday.

Born with her twin sister Paola (who died in 2000 aged 91) to a Jewish family in Turin in 1909, Levi-Montalcini went to medical school, despite the objections of her father. He worried that her work as a doctor would interfere with her duties of future wife and mother.

"At twenty, I realized that I could not possibly adjust to a feminine role as conceived by my father, and asked him permission to engage in a professional career," Levi-Montalcini wrote in her biography.

"In eight months I filled my gaps in Latin, Greek and mathematics, graduated from high school, and entered medical school in Turin," she added.

She graduated in 1936, but two years later her career was halted by Mussolini's laws banning "inferior races" from academic and professional careers.

Undaunted, Levi-Montalcini set up an improvised laboratory in her bedroom during World War II, and studied the growth of nerve fibers in chicken embryos.

Read more at Discovery News

History Is Key Factor in Plant Disease Virulence

The virulence of plant-borne diseases depends on not just the particular strain of a pathogen, but on where the pathogen has been before landing in its host, according to new research results.

Scientists from the University of California System and the U.S. Department of Agriculture's Agricultural Research Service (USDA ARS) recently published the results in the journal PLoS ONE.

The study demonstrates that the pattern of gene regulation--how a cell determines which genes it will encode into its structure and how it will encode them--rather than gene make-up alone affects how aggressively a microbe will behave in a plant host.

The pattern of gene regulation is formed by past environments, or by an original host plant from which the pathogen is transmitted.

"If confirmed, this finding could add a key new dimension to how we look at microbes because their history is going to matter--and their history may be hard to reconstruct," said Matteo Garbelotto, an environmental scientist at the University of California, Berkeley and co-author of the paper.

Epigenetic factors--for example, gene regulation mechanisms controlled by diet or exposure to extreme environments--are well-known to affect the susceptibility of humans to some diseases.

The new study is the first to show a similar process for plant pathogens.

"Sudden oak death, for example, is one of many pathogens that seemingly came out of nowhere to ravage the forests of California," said Sam Scheiner, a director of the National Science Foundation's (NSF) Ecology and Evolution of Infectious Diseases (EEID) program, which funded the research.

"This study shows that such sudden emergence can happen through rapid evolution, and may provide clues for predicting future epidemics."

The EEID program is a joint effort of NSF and the National Institutes of Health. At NSF, it is supported by the Directorates for Biological Sciences and Geosciences.

Garbelotto said that other scientists hypothesized that gene regulation has an effect on plant pathogens, based on the evolutionary rates of portions of the genome that are known to have an effect on gene regulation.

"Our work provides the concrete evidence those hypotheses were correct," he said.

Researchers showed that genetically identical strains of the sudden oak death pathogen isolated from different plant hosts were strikingly different in their virulence and their ability to proliferate.

They also demonstrated that these traits were maintained long after they had been isolated from their hosts.

"We found that an identical strain placed in two different plant hosts will undergo distinct changes that will persistently affect the strain's virulence and fitness," said Takao Kasuga, a molecular geneticist with the USDA ARS and the lead author of the paper.

The implications for disease control are significant.

Scientists say that it may not be enough to know what strain of pathogens they are dealing with in order to make treatment decisions; it also may be necessary to know how the pathogen's genes are being regulated.

This study shows that gene regulation may be the result of the environments the strain inhabited before being identified.

Garbelotto uses a parallel example of a well-known human pathogen: particular strains of the H1N1 flu virus have been identified as highly virulent, so a diagnosis of one of these strains indicates to doctors that they should treat that flu aggressively.

"But, hypothetically, if you caught one of these aggressive strains of H1N1 from a guy that went to, for example, Paris, it could be 10 times more dangerous. You may never know from whom you got it, and it's even less likely that you'll be able to learn where your infector visited before passing the germ on to you."

In plants, Garbelotto said, tracking a pathogen's history may prove even more difficult.

Correct information could give scientists a new weapon to use against virulent strains of diseases like sudden oak death, which can devastate forests and the ecosystems that depend on them.

The researchers also identified two groups of genes that are capable of affecting virulence and whose expression patterns are indicative of the previous host species they inhabited.

Understanding the regulation of these genes may provide scientists with future approaches to control a disease, such as manipulating gene expression to artificially reduce the aggressiveness of plant pathogens.

While Garbelotto stresses that more study is needed, he says if the paper's findings are confirmed, it could influence not just treatment but policy as well.

"Most countries impose regulations on microbes based on their genetic make up--which ones can and can't cross state and international lines and how they must be transported," he said.

"Our findings suggest that when making regulatory policy, we may also need to identify gene expression levels and take into account the history of a microbe."

Read more at Science Daily