Chapter 10



Chapter 10 Bacteria and Viruses

SECTION 1 Bacteria

Bacteria are one of the smallest and are the simplest organism on the planet. They are also the most abundant. Many bacteria cause illnesses, but scientists have discovered that many bacteria are beneficial to humans and our way of life (from medicine production to food production). We will explore how bacteria are classified and some uses of bacteria as well as unique cell structure. Some of the material should be a review because we have already learned it in previous lessons.

Classifying Bacteria: All organisms on Earth fall into six kingdoms: Protista, Plantae, Fungi, Animalia, Eubacteria, and Archaebacteria. As you can easily tell, bacteria make up the kingdoms Eubacteria and Archaebacteria. These two kingdoms contain the oldest forms of life on earth.

RECALL: Bacteria are single celled organisms that do not have nuclei (nucleus). A cell with no nucleus is called a prokaryote. A prokaryote is capable of cellular respiration, move around, and reproduce. Since the prokaryotes have these features, they can function as an independent organism.

RECALL: Bacteria Reproduction

Most bacteria reproduce by a type of simple cell division known as binary fission. During binary fission the DNS is copied (replicated) and one copy ends up in each new cell. RECALL: Binary fission is NOT mitosis or meiosis, the DNA is replicated and then the cell gets longer and then divides in the middle with one copy of the DNA in each cell.

Bacteria when Conditions are Unfavorable

When the conditions become unfavorable for bacteria, some species will produce thick protective membranes and then they are called endospores. Many endospores can survive freezing, drying out, and even boiling. After the conditions become favorable for the bacteria, the endospores will break open and the bacteria become active again. Some endospores have been estimated to be millions of years old and when scientists improved the conditions the bacteria inside became active again. Ethical Question: Should we try to get bacteria from endospores to become active again after being enclosed for millions of years? Could the bacteria be of such dangerous proportion that we may not be able to stop a disease that it introduces? These are things we have to think about.

Shapes of Bacteria

There are three shapes of bacteria, 1). Bacilla, 2). Cocci, and 3) Spirilla. Bacilla shaped bacteria appear as short rods. Cocci bacteria are spherical shaped. The Spirilla are spiral shaped (like a cork screw).

Locomotion of some Bacteria

Some bacteria have flagella that serve as their source of locomotion (movement). The flagella are whip like structures that spin like a cork screw to move the bacteria through the liquid they are in.

Kingdom Eubacteria

Most bacteria are eubacteria. These bacteria are classified by the way they get their food. Some are consumers, others are decomposers and some are producers. The consumers get their nutrients from other organisms. The decomposers get their nutrients from dead organic matter. The producers are capable of making the nutrients they need through photosynthesis (using the sunlight to produce sugars). The producers, like plants contain chlorophyll that captures the energy from the sunlight.

Some bacteria producers are called cyanobacteria, and they live in many different types of water environments. Cyanobacteria have chlorophyll that enables them to carry out photosynthesis. Some scientists have thought that millions of years ago some of the cyanobacteria became adapted to living within cells that had nuclei and as millions of years passed; the adaptations resulted in the first plants being formed.

Kingdom Archaebacteria

Achaebacteria are believed to be ancient bacteria and they are able to survive in environments other organisms living today cannot survive. The environments we find archaebacteria living in are the hot springs and some species survive deep below the ice of Antarctica. Archaebacteria are genetically different from eubacteria. Some archaebacteria do not have cell walls and those that do, the cell walls are chemically different from other organisms.

There are three types of archaebacteria; 1). Heat lovers, 2). Salt lovers, and 3). Methane gas producers. Some heat lovers can survive in temperatures as hot as 360 degrees Celsius (almost 700 degrees F) . Salt lovers live in environments like the Dead Sea, where other forms of life are inexistent. The methane producers give off methane gas where things are decomposing (one place you may find them is in swamps).

SECTION 2 What Do Bacteria Do?

The majority of bacteria are microscopic, in other words we cannot see them without a microscope. Some bacteria are bad for us and some are very beneficial. We often only hear about the bacteria that cause illness and death, so we think all bacteria are bad.

Nitrogen Fixation: RECALL: A species of bacteria is capable of taking atmospheric nitrogen and converting it into a form of nitrogen that plants can use. All organisms must have nitrogen for making proteins and DNA. RECALL: Living organisms that are not producers must get their nitrogen from eating plants and other organisms. Nitrogen enters organisms as they feed on plants and other organisms and when the living organism dies and decomposes, the nitrogen is released back into the soil. Some plants may take this in or a different species of bacteria may consume it and convert it back into atmospheric nitrogen. This is the nitrogen cycle. RECALL: Everything is cycled or recycled through nature.

Some bacteria help humans clean up messes that we make. Bioremediation is the use of bacteria and other microorganisms to change pollutants into harmless chemicals. Bacteria are used to clean up certain types of agricultural, industrial and municipal wastes. We have also used species of bacteria to clean up oil spills.

People and Bacteria: The Benefits

Scientists have used bacteria to produce types of medicines, insecticides, cleaners, adhesives, foods and other products we use. Some bacteria have been used to make antibiotics, which are used to kill harmful bacteria and other harmful microorganisms. Scientists have used a species of bacteria to make insulin that diabetics can use. Diabetes is a disease in which a person’s pancreas does not produce enough or good quality insulin. Scientists have learned how to make insulin and the diabetics can inject the insulin into their body to control the level of blood sugar. A too high or low of a blood sugar level can lead to death of organisms.

Scientists have also learned that bacteria can be used to make yogurt, buttermilk, cheese, and sour cream. Scientists have learned how to use lactic acid bacteria to convert the milk sugar into lactic acid, which acts as a preservative and adds flavor to the food. Examples of other foods made by using bacteria in specific ways include: sour dough bread, cheeses, pickles, some sausages, and some vinegars.

HARMFUL BACTERIA

Bacteria that cause diseases are called pathogenic bacteria. Some diseases you may have heard of are dental cavities, ulcers, strept throat, food poisoning, bacterial pneumonia, lyme disease, tuberculosis, leprosy, typhoid fever, and bubonic plague.

Other organisms are also affected by pathogenic bacteria. Plants, animals, protists, fungi and even certain types of bacteria can be harmed by pathogenic bacteria. Some grains, fruits, and vegetables can be damaged by pathogenic bacteria.

SECTION 3 VIRUSES

Many people think viruses are one of the dangerous agents for the survival of humans. A virus is a microscopic particle that invades a cell and takes over the cell and has the cell make copies if the virus, which eventually destroys the cell and when the cell ruptures all of the copies of the virus are released to invade more cells. Viruses are not living, but the do contain protein and nucleic acids (they are not considered living because they cannot reproduce themselves without controlling a cell, they must use a different cell to do this, they cannot live on their own, they do not eat, grow or breathe.

Again, viruses invade a cell and instruct the cell to produce viruses instead of new healthy cells. The virus must have a host cell to invade and make new viruses. A host is an organism that supports a parasite. Viruses are not cells; they do not have cytoplasm or organelles.

Classifying Viruses

Viruses can be grouped into the type of disease they cause, their life cycle, or the type of genetic material they contain. Viruses can also be classified by their basic shape. Some are cylinders, some are crystals, some are spheres, and some look like spacecraft.

How Viruses Work

Viruses find a host cell and inject their nucleic acids and proteins into the cell. The virus then takes control of the cell and makes copies of it. As the host cell is destroyed and breaks open, new viruses are released to invade more host cells. Now the cycle can start again to produce even more viruses. This cycle is called the lytic cycle. When viruses first enter the host cell they allow the cell to copy itself and then the virus end up in two different cells and as this occurs, the virus is utilizing the host cell to make more. The cycle of allowing the host cell to copy itself is known as the lysogenic cycle.

STUDY GUIDE SECTION 1

1. ___________ are one of the smallest and are the simplest organism on the planet.

2. All organisms on Earth fall into ____________ kingdoms.

3. The two kingdoms of bacteria are the ___________________ and the _______________________.

4. Bacteria are in two kingdoms, the “ancient” bacteria are in the _________________________ kingdom.

5. A cell with no nucleus is called a _____________________.

6. Bacteria are classified as prokaryotic because they do not contain a _______________________.

7. Most bacteria reproduce by a type of simple cell division known as ______________ __________________.

8. When the conditions become unfavorable for bacteria, some species will produce thick protective membranes and then they are called _______________________.

9. ___________________ shaped bacteria appear as short rods.

10. ___________________ bacteria are spherical shaped.

11. The ________________ are spiral shaped (like a cork screw).

12. Some bacteria have __________________ that serve as their source of locomotion (movement).

13. Most bacteria are in the kingdom of ____________________.

14. _____________________ bacteria have chlorophyll that enables them to carry out photosynthesis and some scientists believe this bacteria help bring rise to the first plant life.

15. _______________________ are believed to be ancient bacteria and they are able to survive in environments other organisms living today cannot survive.

16. The three types of Archaebacteria are the ____________________ lovers, _____________________ lovers, and the _____________________ producers.

STUDY GUIDE SECTION 2

1. The majority of bacteria are ________________________.

2. some bacteria carry out ________________________ ____________________, which is taking atmospheric nitrogen and converting it into a form of nitrogen plants can use.

3. Living organisms that are not producers must get their nitrogen from eating _______________________ and other _____________________.

4. Nitrogen in organisms is used to produce _____________________ and ______________________________.

5. __________________________ is the use of bacteria and other microorganisms to change pollutants into harmless chemicals.

6. List some foods in which we use bacteria to produce. ____________________ ___________________________________________________________________________________________________________________________________.

7. Bacteria that cause diseases are called ___________________ bacteria.

8. Pathogenic bacteria can cause diseases like _______________________________ ___________________________________________________________________________________________________________________________________.

9. Are humans the only organisms affected by pathogenic bacteria? ________What other organisms can they affect? _______________________________________.

STUDY GUIDE SECTION 3

1. Many people think _________________ are one of the dangerous agents for the survival of humans.

2. Explain why bacteria are not considered living. __________________________ _____________________________________________________________________________________________________________________________________________________________________________________________________.

3. The four shapes of viruses are _____________________________, ___________________________________, ____________________________, and _____________________________________.

4. The cycle of a virus invading a cell and resulting in more viruses being released to invade more host cells is known as the ________________________.

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