The Room Between the Floorboards Audiobook | Toni Bunnell | olfinperi.tk
Biologists assume that soil organisms make antibiotics to beat back the microbial competition and to establish their territory, Wright says, although the chemicals may also serve other, less-understood functions. Whatever the case, Wright and his students began combing through the DNA of soil microbes like streptomyces to better understand their impressive antibiotic-making powers.
In doing so the researchers stumbled upon three resistance genes embedded in the DNA that Streptomyces toyocaensis uses to produce the antibiotic teicoplanin. While Wright was not surprised that the bug would carry such genes as antidotes to its own weaponry, he was startled to see that the antidote genes were nearly identical to the resistance genes in vancomycin-resistant enterococcus VRE , the scourge of American and European hospitals.
If only we had done this experiment 15 years ago, when vancomycin came into widespread use, we might have understood exactly what kind of resistance mechanisms would follow the drug into our clinics and hospitals. So he handed out plastic bags to students departing on break, telling them to bring back soil samples. Over two years his lab amassed a collection that spanned the continent.
Every one proved resistant to multiple antibiotics, not just their own signature chemicals. On average, each could neutralize seven or eight drugs, and many could shrug off 14 or In all, the researchers found resistance to every one of the 21 antibiotics they tested, including Ketek and Zyvox, two synthetic new drugs.
As in a game of telephone, each time a gene gets passed from one microbe to another, slight differences develop that reflect the DNA dialect of its new host. The resistance genes bedeviling doctors had evidently passed through many intermediaries on their way from soil to critically ill patients.
Wright suspects that the antibiotic-drenched environment of commercial livestock operations is prime ground for such transfer. Nobody knows how long free-floating DNA might persist in the water. A study by University of Illinois microbiologist Roderick Mackie documented this flow. When he looked for tetracycline resistance genes in groundwater downstream from pig farms, he also found the genes in local soil organisms like Microbacterium and Pseudomonas, which normally do not contain them.
Since then, Mackie has found that soil bacteria around conventional pig farms, which use antibiotics, carry to 1, times more resistance genes than do the same bacteria around organic farms. An even more direct conduit into the environment may be the common practice of irrigating fields with wastewater from livestock lagoons. About three years ago, David Graham, a University of Kansas environmental engineer, was puzzled in the fall by a dramatic spike in resistance genes in a pond on a Kansas feedlot he was studying.
At the end of the summer, feedlots receive newly weaned calves from outlying ranches. They still used antibiotics, but more discriminately. Bacteria make up about one-third of the solid matter in human stool, and Scott Weber, of the State University of New York at Buffalo, studies what happens to the antibiotic resistance genes our nation flushes down its toilets. Conventional sewage treatment skims off solids for landfill disposal, then feeds the liquid waste to sewage-degrading bacteria. The end result is around 5 billion pounds of bacteria-rich slurry, or waste sludge, each year.
Around 35 percent of this is incinerated or put in a landfill. Close to 65 percent is recycled as fertilizer, much of it ending up on croplands. Weber is now investigating how fertilizer derived from human sewage may contribute to the spread of antibiotic-resistant genes. Every tested strain in a dirt sample proved resistant to multiple antibiotics.
Most treatment plants, Weber explains, gorge a relatively small number of sludge bacteria with all the liquid waste they can eat.
The result, he found, is a spike in antibiotic-resistant organisms. Or is it coming from sewage-digesting sludge bacteria that are taking up the genes from incoming bacteria? The answer is important because sludge bacteria are much more likely to thrive and spread their resistance genes once the sludge is discharged into rivers in treated wastewater and onto crop fields as slurried fertilizer. On a hopeful note, he has shown that an alternative method of sewage processing seems to decrease the prevalence of bacterial drug resistance. In this process, the sludge remains inside the treatment plant longer, allowing dramatically higher concentrations of bacteria to develop.
For reasons that are not yet clear, this method slows the increase of drug-resistant bacteria. It also produces less sludge for disposal. Unfortunately, the process is expensive. Drying sewage sludge into pellets—which kills the sludge bacteria—is another way to contain resistance genes, though it may still leave DNA intact. Trolling the waters and sediments of the Cache la Poudre, Storteboom and Pruden are collecting solid evidence to support suspicions that both livestock operations and human sewage are major players in the dramatic rise of resistance genes in our environment and our bodies.
All this makes resistance genes a uniquely troubling sort of pollution. For years the livestock pharmaceutical industry has played down its role in the rise of antibiotic resistance. Its members sell an estimated 20 million to 25 million pounds of antibiotics for use in animals each year, much of it to promote growth. For little-understood reasons, antibiotics speed the growth of young animals, making it cheaper to bring them to slaughter. The Union of Concerned Scientists and other groups have long urged the United States to follow the European Union, which in completed its ban on the use of antibiotics for promoting livestock growth.
Such a ban remains far more contentious in North America, where the profitability of factory-farm operations depends on getting animals to market in the shortest possible time.
On the other hand, the success of the E. For instance, the FDA is considering approval of cefquinome for respiratory infections in cattle. As of press time, the FDA had yet to reach a decision. Image courtesy of Jessica Snyder Sacs Consumers may contribute to the problem of DNA pollution whenever they use antibacterial soaps and cleaning products. These products contain the antibiotic-like chemicals triclosan and triclocarban and send some 2 million to 20 million pounds of the compounds into the sewage stream each year.
Triclosan and triclocarban have been shown in the lab to promote resistance to medically important antibiotics. Worse, the compounds do not break down as readily as do traditional antibiotics. He has found even greater levels of these two chemicals in sewage sludge destined for reuse as crop fertilizer. According to his figures, a typical sewage treatment plant sends more than a ton of triclocarban and a slightly lesser amount of triclosan back into the environment each year.
He notes that many European retailers have already pulled these products from their shelves. No doctor wants to ignore an opportunity to save a patient from infectious disease, yet much of what is prescribed is probably unnecessary—and all of it feeds the spread of resistance genes in hospitals and apparently throughout the environment.
Infections are often treated longer than necessary, and multiple antibiotics are given when one would work as well. Late in the afternoon, Storteboom drives past dairy farms and feedlots, meatpacking plants, and fallow fields, 50 miles downstream from her first DNA sampling site of the day. Leaving her Jeep at the side of the road, she strides past cow patties and fast-food wrappers and scrambles down an eroded embankment of the Cache la Poudre River. She cringes at the sight of two small animal carcasses on the opposite bank, then wades in, steering clear of an eddy of gray scum.
According to local legend, the appellation comes from the hidden stashes cache of gunpowder poudre that French fur trappers once buried along the banks. Silbury Hill, a 4,year-old, foot-high mound of chalk and dirt about 80 miles west of London, has finally yielded its ancient secrets.
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It is not the tomb of the long-forgotten King Sil nor the resting place of a golden knight. The story behind the mysterious hill is much less colorful. Silbury Hill is a shrine filled with rocks that, for Stone Age Britons, probably represented the spirits of ancient ancestors. The physical excavation video of Silbury Hill, along with studies using ground-penetrating radar and seismic sonar equipment, has shown that there is not a single human bone in the mound.
Instead, dozens of sarsen stones, a type of sandstone that is also used for Neolithic stone circles like Stonehenge, are buried there. Local geologists think that during the Stone Age, the landscape around Silbury Hill contained hundreds of thousands of sarsen stones. Because the area is made mainly of chalk, prehistoric people would have seen no apparent natural origin for the stones.
Archaeologists think the locals endowed these rocks with a spiritual importance that Silbury Hill still embodies. The area itself is considered sacred by modern pagans, who still make offerings at a nearby spring. Due to conservation laws, the prehistoric holy hill is out-of-bounds to pagans and tourists alike. Name Address 1 Address 2 Tne morning in September, , a former sales representative in his mid-forties entered an examination room with Stanislas Dehaene, a young neuroscientist based in Paris. N, had sustained a brain hemorrhage that left him with an enormous lesion in the rear half of his left hemisphere.
He had once been married, with two daughters, but was now incapable of leading an independent life and lived with his elderly parents. Dehaene had been invited to see him because his impairments included severe acalculia, a general term for any one of several deficits in number processing. To Dehaene, these impairments were less interesting than the fragmentary capabilities Mr.
N had managed to retain. When he was shown the numeral 5 for a few seconds, he knew it was a numeral rather than a letter and, by counting up from 1 until he got to the right integer, he eventually identified it as a 5. He did the same thing when asked the age of his seven-year-old daughter. N still had a similar sense of number. He showed him the numerals 7 and 8.
N was able to answer quickly that 8 was the larger number—far more quickly than if he had had to identify them by counting up to the right quantities. He could also judge whether various numbers were bigger or smaller than 55, slipping up only when they were very close to Dehaene dubbed Mr. If a lesion knocks out one ability but leaves another intact, it is evidence that they are wired into different neural circuits. In this instance, Dehaene theorized that our ability to learn sophisticated mathematical procedures resided in an entirely different part of the brain from a rougher quantitative sense.
Over the decades, evidence concerning cognitive deficits in brain-damaged patients has accumulated, and researchers have concluded that we have a sense of number that is independent of language, memory, and reasoning in general.safilformfa.tk
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Within neuroscience, numerical cognition has emerged as a vibrant field, and Dehaene, now in his early forties, has become one of its foremost researchers. He has approached the problem from every imaginable angle. Working with colleagues both in France and in the United States, he has carried out experiments that probe the way numbers are coded in our minds. He has studied the numerical abilities of animals, of Amazon tribespeople, of top French mathematics students.
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He has used brain-scanning technology to investigate precisely where in the folds and crevices of the cerebral cortex our numerical faculties are nestled. And he has weighed the extent to which some languages make numbers more difficult than others. His work raises crucial issues about the way mathematics is taught. To become numerate, children must capitalize on this instinct, but they must also unlearn certain tendencies that were helpful to our primate ancestors but that clash with skills needed today.
And some societies are evidently better than others at getting kids to do this. In both France and the United States, mathematics education is often felt to be in a state of crisis. The math skills of American children fare poorly in comparison with those of their peers in countries like Singapore, South Korea, and Japan. His surname is Flemish. His father, a pediatrician, was among the first to study fetal alcohol syndrome. Dehaene met Changeux and began to work with him on abstract models of thinking and memory.