Book 1 Reading and Speaking (1108795), страница 5
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Comparing the blue-stain fungus with free-living or pathogenic fungi will shed light on how thebeneficial fungus helps the beetles thrive, she says.Using genomics to stop the bark beetles is a "bit of a long shot, for sure", admits Chris Keeling, a researchassociate in Bohlmann's lab. But it might offer the best strategy for containing the forest pests, which have alreadystarted to jump host species from lodgepole pine, which is found only west of the Rockies, to jack pine, whichstretches east across the entire continent. "We might be able to tweak the system to reduce the beetle populationsor prevent them from spreading further east," Keeling says. (From Nature online, 18 Sept. 2009)Exercise 6. Speak in detail on the multi-species interaction described in this article according to thefollowing plan:1.
What species are involved in the relationship? What is the role of each?2. Why do scientists study this phenomenon on the genetic level?3. What main steps have researchers taken so far? What results have they obtained?4. What are the perspectives of such genomic investigations?Exercise 7. Put the words given in the brackets in the correct word-form.Gene Study Suggests Early Evolution of Land Plants and Fungi Changed Earth's ClimateBy Harald FranzenLand plants and fungi may have arisen far earlier than previously thought, according to a study publishedtoday in the journal Science.
The gene-based research suggests that the (1)_________ (to emerge) of theseorganisms may have led to major climate and animal (2)_________ (to evolve) events.The Pennsylvania State University research team, led by (3)__________ (to evolve) biologist Blair Hedges,based their (4)___________ (to find) on the so-called molecular clock. Genes (5)___________ (to know) toaccumulate (6)____________ (to mutate) at a constant rate, much like a ticking clock, can be used to determinewhen a species originated. To figure out when land plants and fungi originated, the team analyzed 119 suchmolecular clock genes common to (7)___________ (to live) species of animals, plants and fungi.
Their(8)_________ (to result) proved startling. In contrast to fossil-based studies that place the (9)__________ (toappear) of land plants and fungi at around 480 million years ago, the genetic findings indicate that land plants andfungi evolved approximately 700 million and 1,300 million years ago, respectively.The early (10)______________ (to present) of plants and fungi on land would have reduced the amount ofcarbon dioxide in the atmosphere, producing a (11)____________ (to cool) effect, the authors note.
At the sametime, the plants boosted atmospheric oxygen levels, thus paving the way for the (12)__________ (to evolve) ofcomplex animals. (From Scientific American Online, August 10, 2001)Exercise 8. Speak about fungi and their role on our planet. Summarize all the facts which have beendiscussed in this unit.14Unit 4. BacteriaSoap and water and common sense are thebest disinfectants.Sir William Osler, Canadian physician andOxford professor of medicineExercise 1. What do you know about bacteria?1. What is a bacterium? Why are bacteria classified into a separate Kingdom?2. What is the difference between eubacteria and archaebacteria?3.
How are archaebacteria adapted to survive in the extreme conditions of their habitat?4. What processes and mechanisms do bacteria use to obtain energy and nutrients?5. What is the purpose of Gram staining?6. How do bacteria reproduce? What is the difference between binary fission and conjugation?7. What are the functions of bacteria in the environment?8.
What is their significance for humans?9. In what ways do disease-causing bacteria damage human organism?Exercise 2. Explain the following terms in English:prokaryoteantibioticsstrainresistance (to antibiotics)colonynitrogen fixationpathogenobligate aerobesendosporeobligate anaerobescoccusbacillusspirillumStaphylococcus bacteriaStreptococcus bacteriaExercise 3. Read and translate the following text.Antibacterial Products May Do More Harm Than GoodAntibacterial soaps and other cleaners may actually be aiding in the development of superbacteria.By Coco BallantyneTuberculosis, food poisoning, cholera, pneumonia, strep throat and meningitis: these are just a few of theunsavory diseases caused by bacteria.
Hygiene—keeping both home and body clean—is one of the best ways tocurb the spread of bacterial infections, but lately consumers are getting the message that washing with regularsoap is insufficient. Antibacterial products have never been so popular. Body soaps, household cleaners, sponges,even mattresses and lip glosses are now packing bacteria-killing ingredients, and scientists question what place, ifany, these chemicals have in the daily routines of healthy people.Traditionally, people washed bacteria from their bodies and homes using soap and hot water, alcohol,chlorine bleach or hydrogen peroxide.
These substances act nonspecifically, meaning they wipe out almost everytype of microbe in sight—fungi, bacteria and some viruses—rather than singling out a particular variety. Soapworks by loosening and lifting dirt, oil and microbes from surfaces so they can be easily rinsed away with water,whereas general cleaners such as alcohol inflict sweeping damage to cells by demolishing key structures, thenevaporate. "They do their job and are quickly dissipated into the environment," explains microbiologist Stuart Levyof Tufts University School of Medicine.Unlike these traditional cleaners, antibacterial products leave surface residues, creating conditions that mayfoster the development of resistant bacteria, Levy notes. For example, after spraying and wiping an antibacterialcleaner over a kitchen counter, active chemicals linger behind and continue to kill bacteria, but not necessarily all ofthem.
When a bacterial population is placed under a stressor—such as an antibacterial chemical—a smallsubpopulation armed with special defense mechanisms can develop. These lineages survive and reproduce astheir weaker relatives perish. "What doesn't kill you makes you stronger" is the governing maxim here, asantibacterial chemicals select for bacteria that endure their presence.As bacteria develop a tolerance for these compounds there is potential for also developing a tolerance forcertain antibiotics. This phenomenon, called cross-resistance, has already been demonstrated in several laboratorystudies using triclosan, one of the most common chemicals found in antibacterial hand cleaners, dishwashingliquids and other wash products.
"Triclosan has a specific inhibitory target in bacteria similar to some antibiotics,"says epidemiologist Allison Aiello at the University of Michigan School of Public Health.When bacteria are exposed to triclosan for long periods of time, genetic mutations can arise. Some of thesemutations endow the bacteria with resistance to isoniazid, an antibiotic used for treating tuberculosis, whereasother microbes can supercharge their efflux pumps—protein machines in the cell membrane that can spit outseveral types of antibiotics, Aiello explains. These effects have been demonstrated only in the laboratory, not inhouseholds and other real world environments, but Aiello believes that the few household studies may not havebeen long enough. "It's very possible that the emergence of resistant species takes quite some time to occur…; thepotential is there," she says.15Apart from the potential emergence of drug-resistant bacteria in communities, scientists have other concernsabout antibacterial compounds.
Both triclosan and its close chemical relative triclocarban (also widely used as anantibacterial), are present in 60 percent of America's streams and rivers, says environmental scientist Rolf Halden,co-founder of the Center for Water and Health at Johns Hopkins Bloomberg School of Public Health. Bothchemicals are efficiently removed from wastewater in treatment plants but end up getting sequestered in themunicipal sludge, which is used as fertilizer for crops, thereby opening a potential pathway for contamination of thefood we eat, Halden explains. "We have to realize that the concentrations in agricultural soil are very high," andthis, "along with the presence of pathogens from sewage, could be a recipe for breeding antimicrobial resistance" inthe environment, he says.Triclosan has also been found in human breast milk, although not in concentrations considered dangerous tobabies, as well as in human blood plasma.
There is no evidence showing that current concentrations of triclosan inthe human body are harmful, but recent studies suggest that it acts as an endocrine disrupter in bullfrogs and rats.Further, an expert panel convened by the Food and Drug Administration determined that there is insufficientevidence for a benefit from consumer products containing antibacterial additives over similar ones not containingthem. "What is this stuff doing in households when we have soaps?" asks molecular biologist John Gustafson ofNew Mexico State University in Las Cruces.
These substances really belong in hospitals and clinics, not in thehomes of healthy people, Gustafson says.Of course, antibacterial products do have their place. Millions of Americans suffer from weakened immunesystems, including pregnant women and people with immunodeficiency diseases, points out Eugene Cole, aninfectious disease specialist at Brigham Young University.
For these people, targeted use of antibacterial products,such as triclosan, may be appropriate in the home, he says. In general, however, good, long-term hygiene meansusing regular soaps rather than new, antibacterial ones, experts say. "The main way to keep from getting sick,"Gustafson says, "is to wash your hands three times a day and don't touch mucous membranes." (From ScientificAmerican Online, June 07, 2007)Exercise 4. Using the information from the text and other facts you know prove that:1.
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