Georgia Beth - The Hidden World of Bacteria: Multiplying Mixed Numbers

0covercover.xhtmlThe Hidden World of BACTERIA Multiplying Mixed Numbers Georgia Bethcover1page0001page0001.xhtml22page0002page0002.xhtml33page0003page0003.xhtml44page0004page0004.xhtmlTable of Contents A Microscopic Mystery 4 Bacteria Cell 8 Biofilms 21 The Future of Microbiology 24 Problem Solving 28 Glossary 30 Index 31 Answer Key 3255page0005page0005.xhtmlA Microscopic Mystery Bacteria are invisible to the human eye. But, they are all around! The world is crawling with over five nonillion (noh-NIL-yuhn) of them. What does that number look like? It is the digit 5 followed by 30 zeros! There's no question that these microscopic creatures have taken over Earth. Bacteria are one-celled organisms. They are found everywhere. They live underground. They live in human bodies. Bacteria are even strong enough to live deep in the sea. Some types of bacteria have adapted to cold temperatures. They can be found in the frozen tundra. Every person on Earth is covered with bacteria. They can be found on skin and on hair. They live in people's digestive systems, too. They can even affect a person's mood or weight. Bacteria were first discovered in the late 1600s by Antonie van Leeuwenhoek (AN-tuh-nee vahn LAY-vuhn-huhk). He observed bacteria under a microscope. He took notes about what he saw. He recorded their sizes and shapes. But, he was only just beginning to understand their secrets.66page0006page0006.xhtmlAntonie van Leeuwenhoek77page0007page0007.xhtmlVan Leeuwenhoek did not know what he had found. He called them "very little animalcules. " He compared samples of microbes from rainwater, saliva, and other sources. Today, people know that bacteria are 0. 2 to 10 microns wide. That means they are less than 1100 th of an inch (0. 2 millimeters)! They can only be seen with certain magnifying glasses. The lenses magnify bacteria 300 to 1, 000 times their actual size. This makes a cell that is smaller than a dot look as big as a word on this page! These illustrations by van Leeuwenhoek show the animalcules he observed.88page0008page0008.xhtmlThe lenses van Leeuwenhoek used have confused experts. He did not have the powerful lenses that scientists have today. They believe that his lenses would have enhanced cells only 50 to 300 times their size. So, experts think he used something else. But, they are not exactly sure what that was. He kept his method a secret, which he took with him when he died at age 90. Van Leeuwenhoek never told anyone how he made his lenses. His techniques are still a mystery. But, scientists can gather information from the lenses themselves and through his written journals. Van Leeuwenhoek used a microscope similar to this one for his work and drawings. LET'S EXPLORE MATH Van Leeuwenhoek's microscope was about 8 centimeters long. A modern microscope for students is about 4 14 times as tall. Which of the following is the best estimate for the height of a modern microscope? Explain your reasoning. A. a little less than 32 centimeters B. exactly 32 centimeters C. a little more than 32 centimeters99page0009page0009.xhtmlBacteria Cell Bacteria are one of the oldest life forms on Earth. Bacteria fossils have been found in rocks. These fossils date back 419. 2 million to 358. 9 million years. Scientists think that some bacteria have survived over 3 billion years. Form and Function In just one cell, bacteria have what they need to live and grow. Most have a spherical, rodlike, or spiral shape. Many have long thin tails called flagella (fluh-JEL-luh). They help the cell move. A membrane holds the cell together. Ribosomes produce proteins that fuel the cells so they can function. Like all life, bacteria have DNA. DNA is the material that contains all of the information about how a particular living thing looks and functions. But unlike other life forms, bacterial DNA isn't stored in a nucleus. Instead, it's found throughout the cell. Most bacteria use binary fission to reproduce. A single cell grows until it is large enough to split into two identical daughter cells. The process of dividing cells continues. Two cells split into 4 cells. Soon 4 cells become 8, and 8 cells become 16. This continues until there are countless cells. This photo, taken with a microscope, shows a bacterial cell splitting into two cells during binary fission.1010page0010page0010.xhtmlribosome cell wall cell membrane DNA flagellum LET'S EXPLORE MATH Flagella can be longer than their bacteria cells. But, flagella and bacteria are still so small they are measured in micrometers. This is a unit of measurement equal to one-millionth of a meter! Suppose a bacteria cell is 10 micrometers long. Its flagellum is 2 12 times as long. How long is the flagellum? Complete the strategy shown. 10 2 12 = (10 _______) + (_______ 12) = _____________ + _________ = _____________ micrometers1111page0011page0011.xhtmlBacteria's ability to quickly copy themselves helps them evolve over time. Strong bacteria can reproduce faster. They can adapt at a faster rate. When needed, they can adapt to changes in temperature, food, and more. Strong bacteria can survive these changes. Biologist Richard Lenski has studied bacteria for over 25 years. In 1988, Lenski put the same E. coli bacteria into 12 glass flasks. Those groups began feeding and dividing. Since 1988, the 12 groups have made 50, 000 generations of bacteria! Each group is stronger than the last. Lenski wants to find out if they will ever get strong enough that they no longer change. Their rate of change seems to be slowing down. But, they are not stopping. But, there are times when it is not helpful to grow quickly. Some species of bacteria live deep under the ground. It is hard to live there. So, growth rates are much slower. Cells may reproduce once every few thousand years. Bacteria find ways to adapt no matter where they live. E. coli colony1212page0012page0012.xhtmlRichard Lenski LET'S EXPLORE MATH Lenski measured the volume of E. coli samples using femtoliters, which are very small fractions of a liter. Suppose that the volume of the first sample was about 410 of a femtoliter. By the ten-thousandth generation, it increased its volume by 2 34 times. What is the volume of the ten-thousandth generation? Complete the area model and equations to solve the problem. 410 2 34 410 2 = __ 410 34 + = __1313page0013page0013.xhtmlBacteria are causing this sunken ship to corrode. Bacteria develop different colors based on water temperature, as seen here at Yellowstone National Park.1414page0014page0014.xhtmlEffects on Nature Bacteria live in lots of places. They live on polar ice caps. They live in hot springs, too. They can even float through the air. Bacteria continue to change land worldwide. At times, the effects are visible. Bacteria cause the bright colors found in the geysers at Yellowstone National Park. Other times, the effects are not easy to see. Bacteria can eat nearly every substance on Earth. That includes metal! But, they spend most of their time eating the remains of plants and animals. Bacteria can help living things. Bacteria get energy from feeding on debris and waste, such as sewage and compost. This process leaves nutrients in soil for plants. Also, gases released by bacteria after feeding help to nourish new plants and animals. Effects of bacteria on nature are not all positive. Bacteria in food and water can cause diseases in plants and animals. Common blights, such as mildew, fungus, and mold, infect plants and leave them weak. Botulism (BAH-chuh-lih-zehm) is caused by C. botulinum. Botulism is a rare type of food poisoning caused by foods that have not been cleaned properly. It paralyzes chickens, sheep, and cattle. B. anthracis, or anthrax, is another disease. It can kill cows within hours.1515page0015page0015.xhtmlBacterias Effects on Humans Bacteria can make people sick. One common example of this is salmonella. This strain of bacteria causes food poisoning. People can get it by eating raw meat, eggs, milk, or poultry. When infected, people can be ill for two to seven days. Other bacteria can cause a lot of pain. H. pylori forms sores in the stomach. These are called ulcers. Ulcers can be very painful. Infections like these are treated by antibiotics. This medicine is made from microbes. The microbes work to fight and kill bacteria. Only doctors can prescribe this treatment. With proper use, patients can be healed. But antibiotics do not always work. Antibiotics will not help if a virus causes the illness. This is because viruses and bacteria are two different things. Also, antibiotics may kill good bacteria. These help the body fight off infection. Without enough of them, bad bacteria are still able to grow. So, the infection keeps spreading. Bacteria find ways to fight off antibiotics, too. Superbugs are strong bacteria. They have grown resistant to antibiotics. This makes them hard to kill. People can die from superbugs that cannot be treated. H. pylori This H. pylori test shows that a sample tested positive for infection.1616page0016page0016.xhtmlOnly antibiotics prescribed by a doctor for a specific illness should be taken. LET'S EXPLORE MATH Dogs can get bacterial infections, too. Veterinarians treat them with antibiotics. Suppose a small bottle of antibiotics for dogs is 15 milliliters. A large bottle has 5 13 times the volume. 1. Estimate the volume of the large bottle. Explain your reasoning. 2. What is the volume of the large bottle? How does the actual answer compare to your estimate?1717page0017page0017.xhtmlIt is impossible to rid bodies of all bacteria. It would actually be a bad idea! Bacteria help bodies, too. There are lots of microbes in bodies. They create a microbiome in each person. Everyone has a different mix of microbes. They live in organs and cells. The mix of microbes is a balance. Big changes can happen from adding or subtracting these microbes. Bacteria play a big role in gut health. Gut is another name for the stomach or abdomen. In people's guts, there are more than 1, 000 species of bacteria that help digest food. They can make people gain or lose weight. Bacteria in the gut can even affect things that seem unrelated, such as seasonal allergies. Gut health is also closely tied to the health of the entire immune system. The American Gut Project wants to find out how microbiomes vary from person to person. They study how microbiomes and health are related. microbes 3-D image of gut bacteria1818page0018page0018.xhtmlmodel of the human gut LET'S EXPLORE MATH Suppose a microbiologist at the American Gut Project is analyzing microbes in some samples. On Monday, she spends 1 12 hours in the lab. On Tuesday, she spends 2 12 times as long in the lab. 1. How many hours does she spend in the lab on Tuesday? Complete the area model and equations to solve the problem. 1 + 12 2 + 12 1 2 = __ 1 12 = __ 12 2 = __ 12 12 = __ 2. How many hours does she spend in the lab on both days?1919page0019page0019.xhtmlAdding Bacteria With all the bacteria already in bodies, why would anyone add more? Remember that they can help food be digested. Some people take probiotics. These pills contain live bacteria that help other bacteria thrive. To encourage growth of healthy gut bacteria, people can do more than eat probiotics. They can drink them! Kombucha (kom-BOO- chah) is a mix of bacteria and yeast. It's brewed with tea and sugar. Drinking a little each day is an easy way to add new bacteria. Many foods contain probiotics, too. Yogurt, kimchee, and sauerkraut have healthy bacteria. Buttermilk and miso are good sources, too. To ferment these foods, bacteria are added. Over time, the microbes transform the food. Milk turns into yogurt. Soybeans become miso. The process can take months, but the benefits are worth it. Yogurt has been proven to boost digestion. Kimchee can help people lose weight. Sauerkraut may even help fight cancer. Fermented foods taste quite tangy. But, they do more than make dinner more flavorful. They also appear to play a role in mental health. Bacteria tickle nerves in the gut. This signals the brain. More research is needed, but scientists think this process may affect moods and emotions. kimchee pickles sauerkraut yogurt2020page0020page0020.xhtmlLET'S EXPLORE MATH This recipe makes 1 gallon of kombucha. How much of each ingredient is needed to make 3 gallons?