Unit 4. Bacteria

Soap and water and common sense are the best disinfectants.

Sir William Osler, Canadian physician and Oxford professor of medicine

Exercise 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:

prokaryote strain colony pathogen endospore

antibiotics resistance (to antibiotics) nitrogen fixation obligate aerobes obligate anaerobes

coccus bacillus spirillum Staphylococcus bacteria Streptococcus bacteria

Exercise 3. Read and translate the following text.

Antibacterial Products May Do More Harm Than Good

Antibacterial soaps and other cleaners may actually be aiding in the development of superbacteria.

By Coco Ballantyne

Tuberculosis, food poisoning, cholera, pneumonia, strep throat and meningitis: these are just a few of the unsavory diseases caused by bacteria. Hygiene—keeping both home and body clean—is one of the best ways to curb the spread of bacterial infections, but lately consumers are getting the message that washing with regular soap 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, if any, 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 every type of microbe in sight—fungi, bacteria and some viruses—rather than singling out a particular variety. Soap works 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, then evaporate. "They do their job and are quickly dissipated into the environment," explains microbiologist Stuart Levy of Tufts University School of Medicine.

Unlike these traditional cleaners, antibacterial products leave surface residues, creating conditions that may foster the development of resistant bacteria, Levy notes. For example, after spraying and wiping an antibacterial cleaner over a kitchen counter, active chemicals linger behind and continue to kill bacteria, but not necessarily all of them. When a bacterial population is placed under a stressor—such as an antibacterial chemical—a small subpopulation armed with special defense mechanisms can develop. These lineages survive and reproduce as their weaker relatives perish. "What doesn't kill you makes you stronger" is the governing maxim here, as antibacterial chemicals select for bacteria that endure their presence.

As bacteria develop a tolerance for these compounds there is potential for also developing a tolerance for certain antibiotics. This phenomenon, called cross-resistance, has already been demonstrated in several laboratory studies using triclosan, one of the most common chemicals found in antibacterial hand cleaners, dishwashing liquids 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 these mutations endow the bacteria with resistance to isoniazid, an antibiotic used for treating tuberculosis, whereas other microbes can supercharge their efflux pumps—protein machines in the cell membrane that can spit out several types of antibiotics, Aiello explains. These effects have been demonstrated only in the laboratory, not in households and other real world environments, but Aiello believes that the few household studies may not have been long enough. "It's very possible that the emergence of resistant species takes quite some time to occur…; the potential is there," she says.

Apart from the potential emergence of drug-resistant bacteria in communities, scientists have other concerns about antibacterial compounds. Both triclosan and its close chemical relative triclocarban (also widely used as an antibacterial), 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. Both chemicals are efficiently removed from wastewater in treatment plants but end up getting sequestered in the municipal sludge, which is used as fertilizer for crops, thereby opening a potential pathway for contamination of the food we eat, Halden explains. "We have to realize that the concentrations in agricultural soil are very high," and this, "along with the presence of pathogens from sewage, could be a recipe for breeding antimicrobial resistance" in the environment, he says.

Triclosan has also been found in human breast milk, although not in concentrations considered dangerous to babies, as well as in human blood plasma. There is no evidence showing that current concentrations of triclosan in the 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 insufficient evidence for a benefit from consumer products containing antibacterial additives over similar ones not containing them. "What is this stuff doing in households when we have soaps?" asks molecular biologist John Gustafson of New Mexico State University in Las Cruces. These substances really belong in hospitals and clinics, not in the homes of healthy people, Gustafson says.

Of course, antibacterial products do have their place. Millions of Americans suffer from weakened immune systems, including pregnant women and people with immunodeficiency diseases, points out Eugene Cole, an infectious 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 means using 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 Scientific American Online, June 07, 2007)

Exercise 4. Using the information from the text and other facts you know prove that:

1. Hygiene is one of the most important medical achievements of human civilization.

2. Pharmaceutical companies and the media are heavily promoting antibacterial products.

3. There are a lot of traditional substances effective to maintain hygiene.

4. Antibacterial components of modern cleaners stimulate the development of resistant bacteria.

5. Bacteria can develop resistance even to those antibiotics they have never come in contact with.

6. More research is needed to demonstrate the negative effects of antibacterial products in the household.

7. Antibacterial products can contaminate both households and the environment.

8. They can also present potential danger for human health.

9. There are some categories of people who really require additional antibacterial protection.

Exercise 5. Make 15 two-word expressions connected with medical treatment by combining words from the two lists: A and B. Then match each expression with the appropriate phrase below. The first one has been done for you as an example.

A allergic balanced bedside biological bone brain clinical digestive general general heart malignant plastic primary surgical

B anaesthetic attack clock death diet intervention manner marrow practitioner reaction surgery system tooth trial tumour

1. A condition in which the heart has a reduced blood supply because one of the arteries becomes blocked by a blood clot, causing myocardial ischaemia and myocardial infarction (heart attack)

2. A substance given to make someone lose consciousness so that a major surgical operation can be carried out

3. Soft tissue in cancellous bone.

4. The treatment of disease or other condition by surgery.

5. Any one of the first twenty teeth which develop in children between about six months and two-and-a-half years of age, and are replaced by the permanent teeth at around the age of six.

6. Surgery to repair damaged or malformed parts of the body.

7. A condition in which the nerves in the brain stem have died, and the person can be certified as dead, although the heart may not have stopped beating.

8. The way in which a doctor behaves towards a patient, especially a patient who is in bed.

9. An effect produced by a substance to which a person has an allergy, such as sneezing or a skin rash.

10. A trial carried out in a medical laboratory on a person or on tissue from a person.

11. A tumour which is cancerous and can grow again or spread into other parts of the body, even if removed surgically.

12. A doctor who provides first-line medical care for all types of illness to people who live locally, refers them to hospital if necessary and encourages health promotion.

13. The rhythm of daily activities and bodily processes such as eating, defecating or sleeping, frequently controlled by hormones, which repeats every twenty-four hours.

14. The set of organs such as the stomach, liver and pancreas which are associated with the digestion of food.

15. A diet that provides all the nutrients needed in the correct proportions.

Exercise 6. Fighting Bacteria.

Divide into two groups. Each group should read either Text A or Text B about two unusual methods of fighting bacteria. Then in pairs discuss your text with the partner. Try not to miss any details.

Text A. Tea Aids Oral Health

By Sarah Graham

A spot of tea may offer more than just a pleasant way to pass the afternoon. Research findings presented this week at the 103rd General Meeting of the American Society for Microbiology in Washington, D.C. suggests that it can help fight bad breath and may boost the powers of toothpaste.

Christine Wu and Min Zhu of the University of Illinois at Chicago College of Dentistry isolated chemical components of tea leaves known as polyphenols and tested them against three species of bacteria known to cause bad breath. The researchers found that the compounds, specifically catechins and theaflavins, inhibited growth of the oral bacteria over a 48-hour incubation period. What is more, lower concentrations of the chemicals interfered with the enzyme that catalyzes the production of hydrogen sulfide, which has the notorious smell of rotten eggs, and reduced its production by 30 percent. The compounds studied by the scientists are present in both green tea and black tea, although they are more abundant in the latter.

In a second study, researchers reported that green tea may provide additional benefits. Milton Schiffenbauer of Pace University and his colleagues tested tea's ability to fight bacteria that cause infections such as strep throat and dental caries. They found that green tea extracts and polyphenols--particularly those from caffeinated beverages--inhibited bacterial growth. Adding these agents to toothpaste and mouthwash, he notes, may make them more effective at combating microbial agents. (From Scientific American Online, May 21, 2003)

Text B. Scientists Explain Why Vegetable Recipes Skimp on Spices

By Kate Wong

Several years ago, a team of researchers from Cornell University proposed that the spices used in traditional meat-based cuisines originally served not as flavor, but to stave off bacteria and fungi. Now new research is providing further food for thought: findings reported in the June issue of Evolution and Human Behavior explain why vegetable-based dishes tend to lack such spiciness.

Plants, it turns out, don't require so much protection against microorganisms as meats because they have their own natural chemical and physical defenses, which continue to function after cooking. Cornell neurobiologist Paul W. Sherman and undergraduate Geoffrey Hash thus predicted that if spices first served as antimicrobials, especially in warmer climates, vegetable recipes in the same countries surveyed for the meat research should feature fewer spices. Subsequent investigation bore this out. Analyzing 2,129 traditional vegetable recipes from 36 different countries, the team found that spice usage was far lower than that found in meat-based dishes from the same cultures. Indeed, of the 41 spices considered, 38 appear more frequently in meat recipes; the three that don't fit this pattern - sesame, caraway and sweet pepper - offer little protection anyway.

"Humans have always been in a co-evolutionary race with parasites and pathogens in foods, and our cookbooks are the written record of that race," Sherman asserts. "We haven't had to 'run' as hard when we ate vegetables. We haven't had to use extra pharmaceuticals to make vegetables safe for consumption." (From Scientific American Online, July 11, 2001)

Exercise 7. Speak about bacteria and their role on our planet. Summarize all facts which have been discussed in this unit.

Unit 5. Domestic and Domesticated Animals

A horse! A horse! My kingdom for a horse!

William Shakespeare

The Tragedy of King Richard the Third

I have known the horse in war and in peace, and there is no place where a horse is comfortable. The horse has too many caprices, and he is too much given to initiative. He invents too many ideas. No, I don’t want anything to do with a horse.

Mark Twain

Exercise 1. What do you know about domestication of animals?

1. What domestic animals do you know? What wild animals do they come from?

1. What was the first domesticated animal? Why?
2. What purposes were domesticated animals used for?
3. How does the process of domestication take place?

Exercise 2. Read the following two texts (Text A and Text B) about domestication of dogs and goats to check your answers in Exercise 1.

Text A. The Origin of Dogs

Where did our best friend originate? Researchers are looking to DNA to dig up answers about where, when and why pooches became popular

By Katherine Harmon

From Chihuahua to Great Danes, all domestic dogs (Canis familiaris) seem to be descended from the Eurasian gray wolf (Canis lupis). But what we still don't know is exactly when and where our best friends transformed from predators into partners. And such knowledge might help solve the long-disputed question of exactly why dogs were the first animal to be domesticated.

The dog genome was first decoded in 2005—and even before that researchers had been using genetic tools to track Fido's first home. Early research pointed toward east Asia as the locus of first taming after the discovery of high genetic diversity and other key markers in dog populations from various villages there. Some investigators, however, have since pointed out that the genetic search sampled more east Asian village dogs, neglecting similar pups roaming other villages around the globe. That's where the Village Dog Genetic Diversity Project at Cornell University comes in. Starting with a recent genetic analysis of dogs in African villages, the Cornell group hopes ultimately to create a detailed DNA-based map of canine ancestry worldwide, which in turn should provide a new understanding of the ancient humans who took them in.

One part of that new insight appeared earlier this month in the Proceedings of the National Academy of Sciences (PNAS), in a study that calls into question the assumption of dogs' east Asian origin. A team led by Adam Boyko, a researcher at Cornell's Carlos D. Bustamante Lab, sampled 318 village dogs in Africa (as well as hundreds of dogs from North America and Europe for comparison) and discovered that the high genetic diversity of canines there resembles that found in east Asia. "We found almost without exception they're descended from different ancestral populations," Boyko says of the village dogs sampled in Africa. That means they may have been there just as long as others had been in east Asia.

Researchers have also yet to figure out when people first began raising dogs. The going theory is that dogs were domesticated somewhere between 15,000 and 40,000 years ago. But, Boyko explains, genetic testing has not gone deep enough to come up with a more refined date. To try to track down some more clues, field crews have fanned out around the globe this summer to test village dogs in Vietnam, New Guinea, Malaysia and other locations in Eurasia in order to get more data.

Of course, scrappy village dogs aren't often the focus of heartfelt conservation efforts, and some even face active elimination programs. But these pups also have challenges from newly arrived European-descent dogs, which threaten to make a splash in the regional gene pool. "It is unclear the degree to which older populations will be able to maintain their genetic identity and persist in the face of modernity," Boyko and his co-authors wrote in the PNAS paper. So time is of the essence in digging up a solid answer about doggie descent.

Looking back into the pooch family tree will help researchers learn more not only about dogs, but about ancient people, as well. A genetic map of dog domestication could reveal important information about human migration and trade routes. "We may be able to turn dogs into a genetic marker for what human populations were doing," Boyko says. He adds that he and his colleagues also plan to "look for which regions of the genome went under selection earliest," and from that "we'll also learn what traits were selected for at that time." That knowledge, along with a little help from archaeologists, may be able to uncover sniff out just why the dog was so special and became most likely the first domesticated species. (From Scientific American Online, August 20, 2009)

Text B. Gene Study Suggests Goats Got Around Through Early Human Commerce

At the dawn of human history, long migrations were not for weaklings. Early travelers, however, could count on a sturdy, reliable and self-propelling source of food during their trips, a French study has just revealed. Researchers from Joseph Fourier University in Grenoble and the Muse National d’Histoire Naturelle in Paris, in collaboration with scientists from the University of Geneva in Switzerland, discovered that our ancestors likely used goats as "walking larders" some 10,000 years ago. Their findings, which are published on today's issue of the Proceedings of the National Academy of Sciences (PNAS), come from an analysis of DNA extracted from goat mitochondria -small organelles that work as cellular power plants.

The short string of DNA contained in the mitochondria (mDNA) - which accounts for only a small fraction of the total cellular DNA - accumulates mutations at a relatively regular rate and so researchers can use variations in its genes to measure evolutionary changes. The more differences two individuals or species show in the nucleotide composition of their mDNA, the more distantly related they are. Moreover, because mitochondria are only inherited from mothers, the DNA is not subject to the gene shuffling that affects the rest of the genome after fertilization. Therefore mDNA points researchers to only one or a few common female ancestors from which different populations originated.

For their studies, Gordon Luikart from Grenoble University and his colleagues collected mDNA from more than 400 wild and domesticated goats in Europe, Asia, Africa and the Middle East, representing 88 breeds distributed across the Old World. Their results suggest that all of the world's 700 million domestic goats originated from only three ancestors, which were domesticated at different times in different places during prehistory. The first goats were probably domesticated about 10,000 year ago at the dawn of the Neolithic in a region of the Middle East known as the Fertile Crescent.

Intriguingly, the genetic analysis showed that, unlike other domestic animals such as cattle, sheep and pigs, today's descendants of the first domesticated goats are rather evenly distributed in all continents of the Old World. This pattern suggests that goats followed humans in their early migrations. "Goats have been a highly mobile species, probably as small and portable units of human trade throughout history," researchers David MacHugh and Daniel G. Bradley note in a commentary to the PNAS paper.

Goats can live on little food in harsh climates and still provide a major source of meat, skin and fibers for millions of people in the developing world. Strange as it might seem, we should rightfully include those skinny animals in the short list of man's best friends. (From Scientific American Online, May 8, 2001)

Exercise 3. Do you agree with the following statements? Why? Why not? Explain your answer.

1. Studies of animal domestication may shed light on human origin, development and migrations.

2. Scientists know exactly when and where different wild animals were domesticated.

3. Dogs were first domesticated in Africa.

4. Genetic material from numerous breeds and populations of animals is used for investigation.

5. Mitochondrial DNA is used to determine the origin of species.

6. Goats were extremely useful for ancient people.

7. Dogs and goats were domesticated in the same region.

8. All modern goats originate from the same common ancestor.

Exercise 4. Divide into two groups. Each group should read either Text A or Text B on domestication of wild horses. In pairs, share your information with your partner and discuss both texts to combine all the details, so you could answer the questions in Exercise 5.

Text A. DNA Hints at Origins of Domestic Horses

By Sarah Graham

The last sighting of a wild horse population occurred in 1969 in Mongolia. A far more common sight is a domestic horse, whether on a farm or a racetrack. Now scientists have shed new light on how these magnificent beasts came to be controlled by humans. According to a report published online this week by the Proceedings of the National Academy of Sciences, modern horses were domesticated from several distinct ancestral populations. And because horse domestication may have played a key role in the spread of some European languages, the findings could further the study of language evolution.

To track the trail of domestic horses, Thomas Jansen of Biopsytec Analytik in Rheinbach, Germany, and his colleagues sequenced DNA from 318 horses representing 25 different breeds. Specifically, the team analyzed mitochondrial DNA (mtDNA), which is inherited from the mother, and compared the recent samples to previously published DNA data from 334 other animals. The researchers identified 17 distinct types of mtDNA and calculated that at least 77 different wild mares must have been domesticated in order to account for today's domestic horses. Just how these animals were domesticated remains unclear, however. Because of the necessary diversity of the mares, the team posits that several separate and geographically diverse populations participated in the process. One theory holds that domestication occurred independently at a number of locales. Alternatively, the procedure may have slowly spread from a single starting point. In that case, the authors write, "the knowledge and the initially domesticated horses themselves would have spread, with local mares incorporated en route, forming our regional mtDNA clusters." (From Scientific American Online, July 16, 2002)

Text B. Modern Horses Have Many Origins

By Julia Karow

About 6000 years ago, somewhere in the Eurasian grassland steppe, man started to capture and tame wild horses--at least that's what remains from archaeological sites in Ukraine and Kazakhstan, tell scientists. Initially, people did not only use horses for transport, but also for food; at the time, dogs, cows, sheep and goats had already lived with humans for several thousand years. Now genetic evidence from modern and ancient horses, published in today's Science, completes the picture: the taming of horses did not occur in only one place, but in several, geographically distant locations.

Researchers from Sweden and the U.S. analyzed parts of the mitochondrial DNA of 191 domestic horses from ten different breeds, including the Icelandic Pony, the Arabian horse and the (American) Standardbred. They also included DNA sequences from 12,000 to 28,000-year-old horse bones found in Alaska and from 1,000 to 2,000-year-old horse remains from Northern Europe in the comparison. Mothers alone pass on mitochondria to their offspring, which is why the data represents only the maternal line. But the DNA samples from the modern horses differed so much from each other that they probably originated from several different groups of domesticated horses. And the genetic variation within each breed indicates that probably more female horses and only a few studs were used for breeding--a practice that continues today.

Rather than giving away domesticated horses, people in Eurasia probably taught each other techniques for capturing and keeping wild horses from their own area. That's why today's breeds still carry the genetic hallmarks of many different wild populations. (From Scientific American Online, January 19, 2001)

Exercise 5. Answer the following questions:

1. When was a wild horse population seen for the last time?

2. What methods were used to determine the time of horse domestication?

3. What genetic material was used in each study described in the texts?

4. When and where did domestication of horses start?

5. How was domestication of horses performed?

Exercise 6. Make up a list of the 10 key facts about studies of domestication. Agree on the final list of facts with the whole group.

Then summarize everything you now know about domestication of wild animals into one report.

Section 1. Recommended Report and Presentation Topics

1. Seizures: classifications, etiology, treatment.

2. Epilepsy.

3. Malignant tumours.

4. Unique abilities of the human body.

5. Unique abilities of the human brain.

6. Do fresh water and sea water animals drink?

7. What do marine organisms drink?

8. Why is water considered the most valuable resource of the future?

9. Water conservation.

10. Poisonous mushrooms.

11. Symbiotic partnerships inside the human body.

12. Do bacteria packed yoghurts really benefit our health?

13. Extreme bacterial habitats.

14. How did different breeds of domestic dogs originate?

15. Why were cats domesticated?

Section 2.

Unit 6. Brain

I’ll give you my opinion of the human race... Their heart’s in the right place, but their head is a thoroughly inefficient organ.

W. Somerset Maugham

It is good to rub and polish our brains against that of others.

Michel de Montaigne

Exercise 1. What do you know about the human brain?

1. What is the structure of the nervous system?

2. What are the functions of the brain?

3. What is each region of the brain responsible for? Speak about forebrain, midbrain, hindbrain, cerebellum, medulla oblongata, cerebral cortex, etc.

4. What is a neuron?

5. What are the functions of neurotransmitters?

6. What do you know about nerve cell growth (neurogenesis) and neuroplasticity?

7. What is intelligence?

8. What is memory?

Exercise 2. Read introduction to the text. What do you think the possible methods to improve brainpower are?

Six Ways to Boost Brainpower

The adult human brain is surprisingly malleable: it can rewire itself and even grow new cells. Here are some habits that can fine-tune your mind

By Emily Anthes

Amputees sometimes experience phantom limb sensations, feeling pain, itching or other impulses coming from limbs that no longer exist. Neuroscientist Vilayanur S. Ramachandran worked with patients who had so-called phantom limbs, including Tom, a man who had lost one of his arms. Ramachandran discovered that if he stroked Tom’s face, Tom felt like his missing fingers were also being touched. Each part of the body is represented by a different region of the somatosensory cortex, and, as it happens, the region for the hand is adjacent to the region for the face. The neuroscientist deduced that a remarkable change had taken place in Tom’s somatosensory cortex: because Tom’s cortex was no longer getting input from his missing hand, the region processing sensation from his face had slowly taken over the hand’s territory. So touching Tom’s face produced sensation in his nonexistent fingers.

This kind of rewiring is an example of neuroplasticity, the adult brain’s ability to change and remold itself. Scientists are finding that the adult brain is far more malleable than they once thought. Our behavior and environment can cause substantial rewiring of the brain or a reorganization of its functions and where they are located. Some believe that even our patterns of thinking alone are enough to reshape the brain. Researchers now know that neurogenesis (the birth of new neurons) is a normal feature of the adult brain. Studies have shown that one of the most active regions for neurogenesis is the hippocampus, a structure that is vitally important for learning and long-term memory. Neurogenesis also takes place in the olfactory bulb, which is involved in processing smells. But not all the neurons that are born survive; in fact, most of them die. To survive, the new cells need nutrients and connections with other neurons that are already thriving. Scientists are currently identifying the factors that affect the rate of neurogenesis and the survival of new cells. Mental and physical exercise, for instance, both boost neuron survival.

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