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Bacteria and Viruses Ch. 19 Page 470. Bacteria 19-1 Bacteria are prokaryotes Bacteria are prokaryotes That is, they contain no nucleus That is, they contain.

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Presentation on theme: "Bacteria and Viruses Ch. 19 Page 470. Bacteria 19-1 Bacteria are prokaryotes Bacteria are prokaryotes That is, they contain no nucleus That is, they contain."— Presentation transcript:

1 Bacteria and Viruses Ch. 19 Page 470

2 Bacteria 19-1 Bacteria are prokaryotes Bacteria are prokaryotes That is, they contain no nucleus That is, they contain no nucleus

3 Classifying bacteria Eubacteria are organisms like Escherichia coli, or E. coli Eubacteria are organisms like Escherichia coli, or E. coli They contain a cell wall that contains a carbohydrate known as peptidoglycan They contain a cell wall that contains a carbohydrate known as peptidoglycan

4 Archaebacteria Archaebacteria lack the peptidoglycan of Eubacteria and also have different membrane lipids Archaebacteria lack the peptidoglycan of Eubacteria and also have different membrane lipids The DNA sequence is also more like those of Eukaryotes The DNA sequence is also more like those of Eukaryotes

5 Identifying prokaryotes They are identified by shape, cell wall composition, movement, and the way they obtain energy They are identified by shape, cell wall composition, movement, and the way they obtain energy Shape: Bacilli – Rod-shaped bacteria; Spirilla – Spiral and corkscrew shaped bacteria Shape: Bacilli – Rod-shaped bacteria; Spirilla – Spiral and corkscrew shaped bacteria

6 Identifying prokaryotes Cell walls – Bacteria that are gram positive have a thick peptidoglycan layer; Bacteria that are gram negative have thinner walls Movement- Some prokaryotes do not move at all, others are propelled by flagella, whip-like structures used for movement

7 Metabolism Most prokaryotes are heterotrophs, some are autotrophs Most prokaryotes are heterotrophs, some are autotrophs Most heterotrophic prokaryotes must take in organic compounds for food; they are known as chemoheterotrophs. Most heterotrophic prokaryotes must take in organic compounds for food; they are known as chemoheterotrophs. Humans are also chemoheterotrophs which means we compete with some prokaryotes for food! Humans are also chemoheterotrophs which means we compete with some prokaryotes for food!

8 Metabolism-cont. Photoheterotrophs are prokaryotes that are both photosynthetic (use sunlight for energy) and take in their food.

9 Metabolism-cont Autotrophs Autotrophs Photoautotrophs- use light energy to convert carbon dioxide and water to carbon compounds; similar to plants. Photoautotrophs- use light energy to convert carbon dioxide and water to carbon compounds; similar to plants. Chemoautotrophs- Make organic compounds from carbon dioxide. They do not use light energy, they use chemical reactions as energy. Chemoautotrophs- Make organic compounds from carbon dioxide. They do not use light energy, they use chemical reactions as energy.

10 Releasing energy Obligate aerobes are organisms that require a constant supply of oxygen to live. Ex. Mycobacterium tuberculosis Obligate aerobes are organisms that require a constant supply of oxygen to live. Ex. Mycobacterium tuberculosis Obligate anaerobes do not need oxygen, and in fact may be killed by it! Ex. Clostridium botulinum Obligate anaerobes do not need oxygen, and in fact may be killed by it! Ex. Clostridium botulinum Facultative anaerobes can survive with or without oxygen. E. coli Facultative anaerobes can survive with or without oxygen. E. coli

11 Growth and Reproduction Binary fission is a type of asexual reproduction in which bacteria form two identical daughter cells. Binary fission is a type of asexual reproduction in which bacteria form two identical daughter cells. Conjugation involves the formation of a hollow bridge between bacteria and movement of genes from one cell to another Conjugation involves the formation of a hollow bridge between bacteria and movement of genes from one cell to another

12 Growth and Reprodcution-cont Spore formation occurs when growing conditions are unfavorable for bacteria Spore formation occurs when growing conditions are unfavorable for bacteria A thick wall encloses the bacterial DNA and part of its cytoplasm. A thick wall encloses the bacterial DNA and part of its cytoplasm. Spores can wait for months and even years for conditions to improve before they germinate. Spores can wait for months and even years for conditions to improve before they germinate.

13 Importance of Bacteria Bacteria are vital to maintaining the living world. Bacteria are vital to maintaining the living world. Some are producers Some are producers Some are decomposers Some are decomposers Others have human uses Others have human uses

14 Importance of Bacteria-cont Decomposers help maintain equilibrium in the environment by recycling nutrients in an ecosystem. Decomposers help maintain equilibrium in the environment by recycling nutrients in an ecosystem. Nitrogen fixers such as the bacterium Rhizobium convert nitrogen gas into ammonia, a useable form for plants. Nitrogen fixers such as the bacterium Rhizobium convert nitrogen gas into ammonia, a useable form for plants. Human uses- E.coli in our intestine makes vitamins for us that we cannot make ourselves. Human uses- E.coli in our intestine makes vitamins for us that we cannot make ourselves.

15 Viruses A virus is composed of DNA or RNA surrounded by a protein coat A virus is composed of DNA or RNA surrounded by a protein coat The protein coat is called a capsid The protein coat is called a capsid A bacteriophage is a virus that attacks bacteria A bacteriophage is a virus that attacks bacteria

16 Viral Infection Lytic infection – In a lytic infection, a virus enters a cell, makes copies of itself, and causes the cell to burst Lytic infection – In a lytic infection, a virus enters a cell, makes copies of itself, and causes the cell to burst Lysogenic infection – A virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell’s DNA. Lysogenic infection – A virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell’s DNA.

17 Viral infection The viral DNA that is embedded in the host cell’s DNA is called a prophage. The viral DNA that is embedded in the host cell’s DNA is called a prophage.

18 Retroviruses Retroviruses contain RNA as their genetic information Retroviruses contain RNA as their genetic information They get their name from the fact that their genetic information is copied backward, that is from RNA to DNA. They get their name from the fact that their genetic information is copied backward, that is from RNA to DNA. AIDS is a retrovirus AIDS is a retrovirus

19 Bacterial/Viral diseases Pathogens are disease causing agents. Pathogens are disease causing agents. Bacteria produce disease in one of two ways: 1. They break down cells for food. 2. They release toxins that travel throughout the body and interfere with normal activity Bacteria produce disease in one of two ways: 1. They break down cells for food. 2. They release toxins that travel throughout the body and interfere with normal activity

20 Preventing bacterial disease A vaccine is a preparation of killed or weakened pathogens that stimulates the body’s immune system to provide immunity to that disease. Ex. Polio vaccine. A vaccine is a preparation of killed or weakened pathogens that stimulates the body’s immune system to provide immunity to that disease. Ex. Polio vaccine. Antibiotics are compounds that block the growth and reproduction of bacteria. Ex. Penicillins Antibiotics are compounds that block the growth and reproduction of bacteria. Ex. Penicillins

21 Bacterial diseases in Animals Anthrax is a disease that is deadly and can be passed from animals to man Anthrax is a disease that is deadly and can be passed from animals to man It forms spores and is tough to kill. It forms spores and is tough to kill. It has been used as a biological weapon It has been used as a biological weapon Caused by Bacillus anthracis Caused by Bacillus anthracis

22 Controlling bacteria Methods to control bacterial growth include heat sterilization, disinfectants, and food processing Methods to control bacterial growth include heat sterilization, disinfectants, and food processing Heat sterilization involves subjecting bacteria to high temperatures for a prolonged period of time Heat sterilization involves subjecting bacteria to high temperatures for a prolonged period of time

23 Disinfectants Disinfectants are chemical solutions that kill pathogenic bacteria Disinfectants are chemical solutions that kill pathogenic bacteria They include such things as soaps and cleansers. They include such things as soaps and cleansers.

24 Food storage/processing Storing food in a refrigerator slows bacterial growth and reproduction keeping food fresher for a longer period of time Storing food in a refrigerator slows bacterial growth and reproduction keeping food fresher for a longer period of time Canning keeps foods fresh almost indefinitely. Food is sterilized with high heat then placed in sterile containers and sealed. Canning keeps foods fresh almost indefinitely. Food is sterilized with high heat then placed in sterile containers and sealed.

25 Viral diseases Viruses produce disease by disrupting the body’s normal equilibrium Viruses produce disease by disrupting the body’s normal equilibrium Viral diseases cannot be treated with antibiotics Viral diseases cannot be treated with antibiotics Prevention with vaccines is the best treatment Prevention with vaccines is the best treatment

26 Viroids and Prions Viroids are single-stranded RNA molecules with no capsid. They cause diseases in plants. Viroids are single-stranded RNA molecules with no capsid. They cause diseases in plants. Prions are “protein infectious particles” that cause diseases in animals by forming protein clumps. Mad cow disease may be caused by prions. Prions are “protein infectious particles” that cause diseases in animals by forming protein clumps. Mad cow disease may be caused by prions.


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