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Chapter 19 Bacteria and Viruses

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1 Chapter 19 Bacteria and Viruses

2 19-1 Bacteria Bacteria are prokaryotes- unicellular organisms that lack a nucleus. Classification was the Kingdom Monera Now, in two separate Kingdoms: Eubacteria Archaebacteria

3 Bacteria

4 What’s the Difference? Eubacteria- new bacteria
Example: Escherichia coli (E. coli) Found water, land, on and in us. Archaebacteria- ancient bacteria Examples: Methanogens Found in harsh environments: thick mud, digestive tracts of animals, hot springs

5 Identifying Prokaryotes
Shape Cocci – spherical Bacilli – rod shaped Spirilla - spiral

6 How do they obtain energy?
Most are heterotrophs and many are autotrophs Types of heterotrophs: “other” Chemoheterotrophs (chemical) Photoheterotrophs (light) Types of autotrophs: “self” Photoautotrophs (surface of lakes, oceans) Chemoautotrophs (deep ocean)

7 Growth and Reproduction
Can divide every 20 minutes! Two ways to reproduce: Binary fission – dividing in half Conjugation – form bridge and exchange DNA When conditions become unfavorable: Spore formation – help it survive in extreme conditions, such as heat, dryness, lack of nutrients.

8 Binary fission conjugation Spore formation

9 Importance of bacteria
Decomposers – Help ecosystem recycle nutrients by breaking down dead tissue Help in sewage treatment

10 Human Uses Used in industry – clean up oil spills
Remove wastes and poisons from water Make drugs Used in food

11 19-2 Viruses Viruses are composed of a core of DNA or RNA surrounded by a protein coat (capsid) Virus means poison

12 Virus Structures Tobacco Mosaic T4 Bacteriophage Virus Influenza Virus
RNA Capsid proteins Head Tail sheath DNA Tail fiber RNA Capsid Surface proteins Membrane envelope

13 How does a Virus work? Proteins of virus bind to receptors on the surface of a cell. Cell gets “tricked” into letting the viral DNA in. Cell then transcribes and translates viral genes. Bacteriaphage- infects bacteria

14 Viral Replication Two different processes can occur:
Lytic Cycle: viral DNA enters host, copies are made, and cell lyses (bursts). Lysogenic Cycle: viral DNA enters host, viral genes are replicated indefinitely. Prophage- viral DNA incorporated in cell’s DNA

15 The Lytic Cycle...

16 The Lysogenic Cycle...

17 Both Cycles...

18 Retroviruses Retrovirus- contains RNA as its genetic information
Genetic info is copied backwards from RNA to DNA. “Retro” means “backwards” Ex. AIDS is caused by a retrovirus (HIV)

19 Comparison…

20 19-3 Diseases caused by Bacteria and Viruses
Disease causing agents are pathogens Bacteria produce disease in one of two ways: Break down cells for food Release toxins (poisons)

21 Examples for food or toxin release
TB – tuberculosis – destroys lung tissue Strep throat - releases toxins into blood stream


23 Diseases caused by Bacteria
Common Diseases Caused by Bacteria Section 19-3 Diseases caused by Bacteria Disease Pathogen Prevention Tooth decay Lyme disease Tetanus Tuberculosis Salmonella food poisoning Pneumonia Cholera Streptococcus mutans Borrelia burgdorferi Clostridium tetani Mycobacterium tuberculosis Salmonella enteritidis Streptococcus pneumoniae Vibrio cholerae Regular dental hygiene Protection from tick bites Current tetanus vaccination Vaccination Proper food-handling practices Maintaining good health Clean water supplies

24 Controlling Bacteria Sterilization – using high temperatures
Disinfectants – chemical solutions Food storage and processing – storing in fridge or cooking food

25 Preventing Bacterial Disease
Vaccine – weakened or killed pathogen Examples – meningitis, whooping cough Antibiotics – block the growth and reproduction of bacteria Examples- Penicillin or tetracycline

26 Diseases caused by Viruses
Common Diseases Caused by Viruses Section 19-3 Diseases caused by Viruses Type of Virus Nucleic Acid Disease Oncogenic viruses Retrovirus Adenoviruses Herpesviruses Poxviruses DNA RNA Cancer Cancer, AIDS Respiratory infections Chickenpox Smallpox

27 Viral disease in humans
Cannot be treated with antibiotics Vaccines Examples – polio, measles, mumps, chicken pox, hepatitis b

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