Science With Coe Student Authored Textbook
John Coe
Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required)
www.ck12.org
To access a customizable version of this book, as well as other interactive content, visit www.ck12.org
AUTHOR John Coe
CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-source, collaborative, and web-based compilation model, CK-12 pioneers and promotes the creation and distribution of high-quality, adaptive online textbooks that can be mixed, modified and printed (i.e., the FlexBook® textbooks). Copyright © 2015 CK-12 Foundation, www.ck12.org The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by federal, state, and international laws. Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms. Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons Attribution-Non-Commercial 3.0 Unported (CC BY-NC 3.0) License (http://creativecommons.org/ licenses/by-nc/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), which is incorporated herein by this reference. Complete terms can be found at http://www.ck12.org/about/ terms-of-use. Printed: September 16, 2015
iii
Contents
www.ck12.org
Contents 1
Introduction to Bacteria
2
Bacteria 2.1 Bacteria Unit CK12 Links . . . . 2.2 Bacteria Characteristics . . . . . 2.3 Bacterial Nutrition . . . . . . . . 2.4 Reproduction in Bacteria . . . . 2.5 Bacteria and Humans . . . . . . 2.6 Bacteria In The Digestive System 2.7 Bacteria Harmful To Humans . . 2.8 Bacteria Helpful To Humans . .
iv
1
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
4 5 6 10 12 14 16 18 21
www.ck12.org
C ONCEPT
Concept 1. Introduction to Bacteria
1
Introduction to Bacteria
Ivy shivered, though not from cold. It was excitement that caused her quivering. She was headed to the Isobels Academy for Successful Bacteria and Viruses college branch, as her parents had urged her to. The only reason. . . that and seeing a few friends. She hadn’t seen her best friends Emerald, Sandey, Reenie Beanie, and Crystal for several months! She stared up at the Campus gates, awed by the immense doors. She was glad it was located in a secluded corner of Waiohinu, Hawaii. It was in there, but Ivy, like most bacteria, enjoyed the tropical temperature. Swirly Emerald, fusilli Crystal, Sandey a cocci, and a rod shaped Reenie Beanie popped up, jolting me out of my thoughts. “Hi guys! I’m so glad to see you! I said. “MONK-” Emerald’s normal greeting of “monkey cheese” was cut short by the bell. “See ya!” called Emerald, already running toward her first class. “Better get going to home room! I heard the teacher, Mrs. Alexander, is super strict. Be late for her class, and get lines for weeks.” said Emerald. Both Emerald and Crystal’s parent were from Great Britain, and they said things like headmaster instead of principal (they were twins, who had about 50 sets of older twin sisters.). It was interesting to hear her talk. Sandy looked at a watch, and yelped. “Sharks!” I have to be at the opposite end of the campus in 3 minutes!” and ran off. I sighed. “I suppose you have to go too. . . ?” I said to Reenie Beanie. “Unfortunately, yes. However,” she said, grabbing my schedule. “We are in the same classes!” As we ran through the mostly empty halls, I saw bacteria of all types. Bacilli, rod shaped bacteria, ball like bacteria called cocci, and swirly fusilli pasta called Spirilli. We burst into room 34 just as Ms. Alexander called “Ivy Victorie Clover Anastasia McKenzie Amethyst Alexandra Griffin?” “Present!” I yelled out. She looked at me with pursed lips and slitted eyes. “Ms. Griffin, next time you are late, knock.” she said. “Yes ma’am.” I said, resisting the urge to laugh. She looked like she just ate fifteen boxes of warheads and sour patch kids in a row! I was glad when she continued role (which wasn’t in alphabetical order “Emerald Lily Milfoil Rosebay Thornapple Saffron Laburnum Manchineel Nettle Hollowroot Whortleberry Hackett?”) “Present!” “Crystal Cecilia Ilse Hackett?” “Present!” “Amy Honeyzuckle Samantha Ide?” “Present.” “Taylor Tara Ide?” “Present!” “Bryn Piper Simonet?” “Present.” “Brian Pascal Simonet?” “Present.” “Gordon Craig Smitchwith?” 1
www.ck12.org “Present.” “Kinsley Kameraet?” “Present.” “Matthias Kameraet?” “Present.” “Layla Lark Smitchwith?” “Present!” “Adele Honour Kaymer?” “Present.” “Reenie Beanie Sammy Lizzette Klark?” “Present.” Rhiannon Robin Roxene Raven Klark?” “Present.” “Sandy King?” There was no answer. “Celeste Kaymer?” “Present!” It continued for a while. Ms. Alexander started droning about middle school and what was expected at Isobel’s. Before I knew it, it was time for Bacteria; a study. In room 43, Mr. Russell toke role. Then the lesson began. “All bacteria consist of the same structure. First, on the outside, was a capsule with a bacterial flagellum and some pili. Then is a cell wall of peptidoglycan.” he said, sketching a picture as he went on the chalkboard. “Then, there is a plasma membrane. After that is the cytoplasm, with ribosomes and plasmids. In the cytoplasm is a nucleoid with the circular DNA. The cell wall is one of the most important parts of the bacterium in question. The most important part, however, is the nucleoid. This has the DNA, the very thing that makes us living beings. Without it, we would be a blob. No, we would not even exist without it!” Then a hand shot into the air. “Yes, Celeste?” “Mr. Russell, what does DNA stand for?” “Deoxyribonucleic acid, my dear.” he replied. “Now, as I was saying, uh, what was I saying? I lost my train of thought. Yes, Adele?” “You were saying: ’This has the DNA, the very thing that makes us living beings. Without it, we would be a blob. No, we would not even exist without it!” replied Adele. “Thank you Adele. I was not expecting a quote. You must have been paying a lot of attention! All of you should pay as much attention as Adele!” Here Adele blushed because, as everyone behind her could see, she had a recording machine taking in every word he said. “Now, the next part of the lesson says: Many bacteria, almost all, gain energy from the sun. That is why our cafeteria has special tanks of sunlight poured into the cafeteria during your lunchtime. We also need metal ions and ’organic’ carbon, like sugar and fatty acids.” “For every 1 human cell, you have 20 bacteria! That means a human with 100 cells has 2,000 bacteria!” he said next. “Bacteria reproduce asexually, which is basically like putting a bacterium in a copy machine. Sometimes the printer runs out of ’ink,’ making the bacteria look slightly different from the forebear. There is no mother or father; however not all bacteria look the same as their parent due to the fact that the bacteria can ’swap’ DNA with other bacteria. There are three ways that bacteria can swap DNA: Transformation, Conjugation, and Transduction.” He began sketching another picture. It looked something like this: WAYS BACTERIUM SWAP DNA
2
www.ck12.org
Concept 1. Introduction to Bacteria
Then the bell rang. “See you tomorrow!” called Mr. Russell. I couldn’t wait for tomorrow to learn even more!
3
www.ck12.org
C HAPTER
2
Chapter Outline 2.1
BACTERIA U NIT CK12 L INKS
2.2
BACTERIA C HARACTERISTICS
2.3
BACTERIAL N UTRITION
2.4
R EPRODUCTION IN BACTERIA
2.5
BACTERIA AND H UMANS
2.6
BACTERIA I N T HE D IGESTIVE S YSTEM
2.7
BACTERIA H ARMFUL TO H UMANS
2.8
BACTERIA H ELPFUL TO H UMANS
This chapter covers the basics of Bacteria including how they affect humans.
4
Bacteria
www.ck12.org
Chapter 2. Bacteria
2.1 Bacteria Unit CK12 Links Bacteria Unit CK12 links: To see the original works referenced in our text use the links to the CK-12 Bacteria concepts below.
Helpful Bacteria http://www.ck12.org/life-science/Helpful-Bacteria-in-Life-Science/#all Bacteria Nutrition http://www.ck12.org/life-science/Bacteria-Nutrition-in-Life-Science/#all Bacteria Reproduction http://www.ck12.org/life-science/Bacteria-Reproduction-in-Life-Science/#all Bacteria and Humans http://www.ck12.org/biology/Bacteria-and-Humans/#all Harmful Bacteria http://www.ck12.org/life-science/Harmful-Bacteria-in-Life-Science/ Bacteria Characteristics http://www.ck12.org/life-science/Bacteria-Characteristics-in-Life-Science/#all Bacteria of the Digestive System http://www.ck12.org/life-science/Bacteria-in-the-Digestive-System-in-Life-Science/#all
5
2.2. Bacteria Characteristics
www.ck12.org
2.2 Bacteria Characteristics Characteristics Of Bacteria Have you ever wanted to know about Bacteria? Bacteria are single living cells. Bacteria cells are similar to your cells in many ways; yet, they also have very noticeable differences. Bacteria have many unique processes of changing for the better and allowing them to live in many different environments. If you are interested , keep reading!
FIGURE 2.1 A hydrothermal vent. Ancient archaebacteria live here.
Bacteria are the most successful and abundant living things on the planet. They lived on this planet for 2,000,000 years before the first eukaryotes and during that time it evolved into millions of different groups of living things Scientist estimated that planet Earth holds about 145 nonillion=145,000,000,000,000,000,000,000,000,000 bacterial cells. A gram of dirt usually contains about 40,000,000 bacterial cells.
Some bacteria (those known as aerobic forms) can process food only in the presence of free or atmospheric oxygen; others (anaerobic bacteria) cannot grow in the presence of free oxygen but get oxygen from compounds.
Bacteria are grouped in a number of different ways. Most bacteria are of one of three typical shapes—rod-shaped (bacillus), round (coccus, e.g., streptococcus), and spiral (spirillum).
Bacteria are so small that they can only be seen with a microscope. When viewed under the microscope, they have three distinct shapes . Bacteria can be identified and classified by their shape: Bacilli are rod-shaped. Cocci are sphere-shaped 6
www.ck12.org
Chapter 2. Bacteria
FIGURE 2.2 Baccilli bacteria.
FIGURE 2.3 Cocci bacteria.
Spirilli are spiral-shaped
Bacteria are surrounded by a cell wall consisting of peptidoglycan. This complex molecule consists of sugars and amino acids. The cell wall is important for protecting bacteria. The cell wall is so important that some antibiotics, such as penicillin kill bacteria by preventing the cell wall from forming. Some bacteria depend on a host organism for energy and nutrients. These bacteria are known as parasites. If the host starts attacking the parasitic bacteria, the bacteria release a layer of slime that surrounds the cell wall. This slime offers an extra layer of protection. 7
2.2. Bacteria Characteristics
www.ck12.org
FIGURE 2.4 Spirilli bacteria.
FIGURE 2.5 Bacteria - labelled cell.
8
www.ck12.org
Chapter 2. Bacteria
In biology, a species is considered a group of individuals who can interbreed and produce viable offspring. This is a very practical and useful definition, but how do you apply that to organisms that don’t have sex? That don’t mate with other individuals? Well, you can’t, and that is why scientists have come up with techniques to identify species in organisms like bacteria which don’t have sexes.
MEDIA Click image to the left or use the URL below. URL: http://www.ck12.org/flx/render/embeddedobject/105226
9
2.3. Bacterial Nutrition
www.ck12.org
2.3 Bacterial Nutrition Bacteria Nutrition
Plants aren’t the only organisms that use the energy of the sun to make food. Some bacteria can also perform photosynthesis. The first photosynthetic organism on Earth was bacteria. Photosynthesis is one way bacteria gets energy. Bacteria can receive energy from photosynthesis, breaking down chemical compounds, and by breaking down dead organisms and waste. Bacteria is what causes you to pass gas! Bacterial requirements for growth include sources of energy, "organic" carbon (e.g. sugars and fatty acids) and metal ions (e.g. iron). Best temperature, pH and the need (or lack of need for oxygen) are important. Obligate aerobes must grow in the presence of oxygen. They cannot carry out fermentation. Bacteria is important for a human body to get rid of unnecessary objects in the human body. You are up to a large degree made up of this bacteria. You’re not just made up of one type of bacteria you are made up of thousands. For every 1 human cell you have 20 bacteria. If you have 10 to 100 trillion cells you would have 200 to 2000 bacteria. Some of the bacteria are friendly and the others can be very deadly. Bacteria is 10% of your mass. So if you weigh 100 pounds you have 10 pounds of bacteria walking around with you. Bacteria uses the nutrition in your body to get rid of excessive air and waste that your body needs to get rid of.
FIGURE 2.6 Computer generated example of bacteria.
Presentation Link - (elaboration on some subjects): http://www.movenote.com/v/t6jXbG1BeCB - movenote
10
www.ck12.org
Chapter 2. Bacteria
MEDIA Click image to the left or use the URL below. URL: http://www.ck12.org/flx/render/embeddedobject/108399
Vocabulary: Photosynthesis - The process of plants using the sun to create energy. Compound - Consisting of multiple elements Obligate - Restricted to a particular function or state Aerobes - An organism that can survive and grow in an environment with oxygen Fermentation - A process converting sugar to acids Anaerobes - An organism that grows without air, or requires oxygen-free environments to live (opposite of aerobes - just wanted to put that in)) Nutrition - the process of providing or obtaining the food necessary for health and growth Chemical - of or relating to chemistry or the interactions of substances as studied in chemistry. Review Quiz:
https://docs.google.com/a/lkstevens.wednet.edu/forms/d/1jTh16QYfYc9Dg8YGEedNYMHAGwBLemYia3IvX24BP6k/viewfo Try It Out its the most amazing thing you will ever experience (not really it will help you at least. . . )
11
2.4. Reproduction in Bacteria
www.ck12.org
2.4 Reproduction in Bacteria How Does Bacteria Reproduce?
FIGURE 2.7 Binary fission in bacteria.
Bacteria reproduce asexually, meaning that there are no mother and father of bacteria . Binary fission is when the chromosome copies itself, forming two identical copies. Then the chromosome gets bigger and bigger and divides into two more daughters. Sometimes it looks exactly like the bacteria that produced it. However, the bacterium doesn’t exchange DNA but the “child” doesn’t always look the same. The new bacteria are considered clones (copies), but not all bacteria are clones. Sexual reproduction doesn’t occur with bacteria. They can swap DNA with other bacteria, which don’t make them clo nes. Three ways bacteria swap DNA are: Conjugation- when DNA runs through an extension on the outside of a single bacteria (germ) and travels from one bacterium to the other. Another way is Transduction, the process of a virus carrying DNA from one bacteri um to another bacterium . Transformation is where a bacterium picks up DNA from its surrounding environments.
FIGURE 2.8 Methods of DNA exchange in bacteria.
12
www.ck12.org
Chapter 2. Bacteria
MEDIA Click image to the left or use the URL below. URL: http://www.ck12.org/flx/render/embeddedobject/108368
Glossary: Asexual Reproduction: A process of forming a child from a single parent. Or just a parent making a copy of itself. Binary Fission: This is a type of asexual reproduction in bacteria, where a single cell divides into two cells. In other words it’s when one cell splits and becomes two cells. Gender: man or woman DNA: A self replicating material present in nearly all living organisms. Conjugation: Transfer of DNA from one bacterium (bacteria) to another. Transduction: When a virus carries DNA from one bacteria to another bacteria Transformation: Picking up pieces of DNA from a bacterium (germ) environment. Chromosome: A threadlike construction of nucleic acids and protein.(normally different colors)
13
2.5. Bacteria and Humans
www.ck12.org
2.5 Bacteria and Humans Click here before you read Benefits of Bacteria Bacteria gives lots of help to the environment. It is kind of like a lot of tiny janitors going around and seeing what needs to be done. Bacteria doesn’t just make you sick. It has other jobs too. For example, bacteria is a very important because it helps dissolve bad things in your body and the world around you. Did you know that bacteria breaks down the food you eat? Yes, so you can thank bacteria for some trips to the bathroom. Humans also use bacteria to: - create products such as alcohol you drink and the molecules that break up bigger chemicals -making drugs such as the medicine you take when you get the flu -making gases -cleaning up oil spills and poisonous wastes -killing plant pests -rotting foods
FIGURE 2.9 E. Coli in the human intestines.
MEDIA Click image to the left or use the URL below. URL: http://www.ck12.org/flx/render/embeddedobject/108401
Bacteria and Disease 14
www.ck12.org
Chapter 2. Bacteria
You have ten times as many bacteria as cells in your body. Most of these bacteria won’t hurt you. However, bacteria can also make you very sick. Food poisoning can be caused by bacteria. Bacteria may spread from one person to another. For example, a sickness, like a cold or flu can be spread through touching, coughing, or sneezing. They may also spread by food, water, or other objects. Humans have literally walked into some new sicknesses caused by bacteria. When humans come into contact with different people, they may enter a cycle where diseases are spread. Consider Lyme disease. It is caused by bacteria that normally infect small, wild mammals, such as mice. A very small bug, called a tick bites a mouse and picks up the bacteria. The tick may then bite a human who invades the home of the tick. Through the bite, the bacteria are sent into to the human’s body. Controlling Bacteria Germs in food or water usually can be destroyed by the making temperature hotter. Germs on many things can be killed with bleach or other infection fighting chemicals. Bacterial infections in people can be treated with medicine. For example, if you ever had a sore throat, you were probably treated with medicine that fights one kind of germ. Medicines have saved many lives. However, using it wrong, or taking too much of the medicine, have led to antibiotic resistance ( resistance is where someone or something will not do or take something. For example, I refuse to clean my room, or I refuse to do my homework) . In germs, antibiotic resistance is when a germ is no longer affected by the medicine that should kill it, because you have taken so much, that the germ has found a way to make the medicine harmless. These infections are very hard to deal with.
15
2.6. Bacteria In The Digestive System
www.ck12.org
2.6 Bacteria In The Digestive System ~Bacteria in the Digestive system~
Did you know that most of the bacteria in your body is in your digestive system? The human body carries about 100 trillion small living things, or organisms, in its intestines. Intestinal bacteria help make vitamin B and vitamin K, as well as metabolising, bile acids, sterols, and xenobiotics.Vitamin K is a vitamin we need to posttranslational change of certain proteins required for blood coagulation, and in (related to how the body uses food) pathways in bone and other tissue.Vitamin B is a group of vitamins that dissolve in water. Vitamin b6 helps your cells absorbs energy, and use it. Vitamin b12 is good for your brain. It helps you remember things and send messages to and from your brain. There are 10 other b vitamins that help strengthen your skin and bones, and a couple can even help prevent cancer.
FIGURE 2.10 Human flora.
Bacteria make up most of the flora in the colon and up to 60% of the dry mass of feces. Over 99% of the bacteria in your body are anaerobes. Anaerobes are tiny living things that don’t use need oxygen to live.
Vocabulary: Organism - any contiguous living system Bile Acid - steroid acids found mainly in the bile of mammals. Sterols- a subgroup of the steroids and an important class of organic molecules. Xenobiotics - a chemical which is found in an organism but which is not normally produced or expected to be present in it. 16
www.ck12.org
Chapter 2. Bacteria
Posttranslational- a step in protein life making. Coagulation - the process by which blood forms clots
MEDIA Click image to the left or use the URL below. URL: http://www.ck12.org/flx/render/embeddedobject/108403
17
2.7. Bacteria Harmful To Humans
www.ck12.org
2.7 Bacteria Harmful To Humans HARMFUL BACTERIA
Bacteria is everywhere but not all bacteria is harmful. But bad bacteria makes you sick like the kind called Pat O’Gen. While other bad bacteria spoil your food and water. Bacteria can multiply fast so that means one bad bacteria can spoil your food or make you sick. If environment is not clean and dirty more bacteria will be there because they love it when conditions are like this.info from- http://microbemagic.ucc.ie/about_microbes/bad_bacteria.html This bacteria, called Mycobacterium tuberculosis causes the disease Tuberculosis (TB). These bacteria usually attack the lungs. If left untreated, the infection can be fatal. Many other illnesses, mild and severe, are also caused by certain types of bacteria. Strep throat Tuberculosis Pneumonia Leprosy Lyme disease Luckily most of these can be treated with antibiotics. (CK-12 Foundation)
FIGURE 2.11 Lyme disease.
Some bacteria also have the potential to be used as biological weapons by terrorists. An example is anthrax, a disease caused by the bact erium Bacillus anthracis . Inhaling the spores of this bacterium can lead to a deadly infection, and, therefore, it is a dangerous weapon. Food contamination In 2001, an act of terrorism 18
www.ck12.org
Chapter 2. Bacteria
in the United States involved Bacillus anthracis spores Bacillus anth racis spores is when a spore is a dehydrated cell with thick walls and additional layers that form inside the cell membrane. It can remain inactive for many years, but if it comes into a favorable environment, it begins to grow again. It is sometimes call ed an endospore , because it initially develops inside the rod-shaped form. Features such as the location within the rod, the size and shape of the endospore , and whether or not it causes the wall of the rod to bulge out are characteristic of particular spe cies of Bacillus. Depending upon the species, the endospores are round , oval, or occasionally cylindrical. They are highly refractile and contain dipicolinic acid. Electron micrograph sections show that they have a thin outer spore coat, a thick spore cort ex, and an inner spore membrane surrounding the spore contents. The spores resist heat, drying, and many disinfectants (including 95% ethanol). [3] Bacterial contamination of foods can lead to digestive problems, an illness known as food poisoning. Raw eggs and undercooked meats commonly carry the bacteria that can cause food poisoning. Food poisoning can be prevented by cooking meat thoroughly and washing surfaces that have be en in contact with raw meat. Washing your hands before and after handling food also helps prevent contamination. (CK12)
Wikipedia
FIGURE 2.12 This bacteria causes tuberculosis.
This bacterium, called Mycobacterium tuberculosis, causes the disease Tuberculosis (TB). These bacteria usually attack the lung
Bacteria can be deadly, and it lives anywhere in a stable climate or and unhealthy area in the world. When you have a cold, or your sick, we take antibiotics, a medicine we take to cure our sickness that we have. There is a thing called food poisoning, whic the bacteria from food that you eat, makes your body sick.Strep throat comes from a bacteria infection that makes your throat red,and makes your throat swell like a big marshmallow.
Sometimes people get the cold from someone they know that sneezed and you breathed in and you got the virus that couldn’t liv which could even get you the flu!!!! which isn’t good. Did you know that when you cough, your body is telling you that they are have.
19
2.7. Bacteria Harmful To Humans
www.ck12.org
FIGURE 2.13
20
www.ck12.org
Chapter 2. Bacteria
2.8 Bacteria Helpful To Humans Helpful Bacteria
When the average person hears the word “bacteria” they think of getting a cold or fever, or something that’s like one. However, in reality, we humans couldn’t live without bacteria. Bacteria plays a big part in the human body and world around us, they are parts that we cannot see. Digestive system
FIGURE 2.14 E. Coli
One helpful thing it does is help process food in our digestive system, which is important to a person’s health. There are species of bacteria such as E. coli (although it is possible to get an E. Coli infection) that help us break down and weaken our food that we have eaten. There are even more bacteria than human cells in some parts of your body. Where are these good bacteria? They are all around our body, but E coli is in our intestines. We usually are born with the healthy bacteria in our system, but that doesn’t mean that all bacteria are harmful to humans or animals. Decomposers Decomposers, when you hear that word you think worms; but in this situation we are referring towards bacteria. Bacteria are a very important decomposer, bacteria breaks down dead materials, waste products, and recycle nutrients gets put back into the environment. We humans get our nutrients from food, but plants get theirs from soil. They are able to do so because bacteria breaks down dead materials and put them back into the environment, which then plants can take the nutrients out of the soil. The last way bacteria is so important is because without it eventually we could run out of materials to survive.
Medicine
21
2.8. Bacteria Helpful To Humans
www.ck12.org
FIGURE 2.15 Fungi are also decomposers, along with bacteria.
You probably think that bacteria are a nasty, bad thing that makes you sick. Wrong! Well, right and wrong. Yes, there are bad types of bacteria that make you sick; but there are also good types of bacteria that help you feel better. Bacteria can be used to make chemicals and medicines that we need. For example, bacteria are essential to fighting cancer! They help to build a strong immune system that digests candids, yeasts and foreign microbes. Without bacteria, fighting cancer would be harder than it already is! Food Bacteria Ok, by now you probably know how bacteria helps you to digest, how they are used in medicine, and how they help you decompose bad things in your body! Wait a minute, what about bacteria that is in your everyday food? That’s right, bacteria actually creates some of your favorite foods. Like cheese? Well, did you know that that cheese would just be milk if bacteria hadn’t been present while it was being made? Why does bacteria need to be in foods like 22
www.ck12.org
Chapter 2. Bacteria
cheese and yogurt though? There is a very great reason, have you ever noticed how yogurt and cheese kind of have a waxy or a thick feel to it? When bacteria is in the mixture of, let’s say milk, it has a reaction with the milk, it eats the sugars in the milk, then it poops the sugars out in the form of an acid that makes it has that feel to it, this is known as Fermenting. So, next time you eat cheese, say thank you to your bacteria friends! So we learned that bacteria play an important part in our life, not to mention all life around us. It’s in our food, helping it to produce. Bacteria’s in our medicine, helping us create the chemicals and medicines we need. It also helps out with decomposing, making sure we have the things we need to survive. Bacteria also help us digest our food! So the next time you go to buy hand sanitizer that harms bacteria, think twice. We need the creatures around.
MEDIA Click image to the left or use the URL below. URL: http://www.ck12.org/flx/render/embeddedobject/108409
The text has beed re-edited by students with the challenge of writing a better textbook for middle school students. This is their first attempt at re-writing a textbook. All images are either from the origninal CK12 book or gathers from CC licensed material. The students are learning to cite material, so we apologize for any missing references.
23