1. Chapter 19 Bacteria & Viruses

2. Under the Microscope
Microorganisms are living things that can only be seen through a microscope. Imagine that you have just discovered a new microorganism. The first thing that you want to do is to tell the scientific community all about your new discovery.

3. 1. Describe your microorganism in detail.
2. Describe its habitat.
3. Classify your microorganism by giving it a genus and species based on its characteristics. (Ex: Homo sapien)

4. Bacteria - Prokaryotes
are classified into the kingdoms of
Eubacteria
Archaeabacteria
include a variety of lifestyles such as
live in harsh environments such as
Infecting large organisms
Thick mud
Living in soil
Animal digestive tracts
Salty lakes
Hot springs

5. Eubacteria vs. Archaebacteria
Live almost anywhere
Surrounded by a cell wall made of peptidoglycan
Gram-positive: thick walls that retain the dark stain
Gram-negative: thinner walls inside outer lipid layer. Alcohol dissolves lipid and the bacteria appear pink or light red

6. Archaebacteria Lack peptidoglyan Different membrane lipids
Live in extreme environments

7. Metabolic Diversity Heterotrophic Bacteria Autotrophic Bacteria
Chemoheterotrophs
Photoheterotrophs
Autotrophic Bacteria
Photoautotrophs
Found near surface of lakes & streams
Ex: Cyanobacteria
Chemoautotrophs
Perform chemosynthesis: Use energy from chemical rxns involving ammonia, sulfur iron etc.

8. Releasing Energy Obligate Aerobes: Require constant supply of oxygen
Ex: Mycobacterium tuberculosis
Obligate Anaerobes: Live in absence of oxygen
Ex: Clostridium botulinum
Facultative anaerobes: Survive with or without oxygen
Ex: E. coli

9. The Structure of a Eubacterium
Peptidoglycan
Cell wall
Cell membrane
Ribosome
Flagellum
DNA
Pili

10. Growth & Reproduction
Binary Fission: Asexual, bacterium grows, DNA is replicated and the cell divides in half.
Conjugation: Transfer of genetic information via “a bridge”
Identical daughter cells
Increased genetic diversity

11. Growth & Reproduction
Spore Formation: Occurs when bacteria are in “unfavorable conditions.” Endospores enclose DNA and some cytoplasm, may remain dormant for long periods of time. When conditions are better, spores germinate and bacterium begin to grow.

12. Importance of Bacteria to Us!
Food & Beverage: Yogurt, olives, pickles, sauerkraut
Industry: Cleaning up oil spills, removing waste products from water
Bio-technology: Used to make drugs such as insulin.
Our Bodies: E.coli make vitamins that our body can’t produce by itself

13. Importance of Bacteria in Nature
Decomposers: Return nutrients to the soil, used in sewage treatment to produce purified water, nitrogen and CO2
Nitrogen Fixers: enrich plants
– Nitrogen is a component of protein.
– Bacteria transform atmospheric nitrogen into an absorbable form, ammonia

14. Viruses – What they mean to you!
If you have ever had a cold, you are probably familiar with the word virus. It is a word that makes most people frown.
1. What do you think of when you hear the word virus? Make a list of all the words you can think of that relate to viruses.
2. What are two things that you would like to find out about viruses?

15. HELP!!!!!!!!!!!!!
1892
Cause of the tobacco mosaic disease discovered
1897
Tiny particles in the juice that caused the disease termed “viruses”
This plant has a disease—as the disease progresses, the leaves turn completely yellow, wither, and fall off killing the plant. Farmers are losing valuable crops. You are in charge……………………..what do you do?

16. What are viruses? Latin word for “posion”
Particles of nucleic acids, protein and sometimes lipids
Reproduce only by infecting living cells
HIV Virus Influenza Virus Rabies

17. Virus Types & Structure
T-4 Bacteriophage
Tobacco Mosaic Virus
Flu Virus
RNA
DNA
Head
Capsid
Capsid Proteins
Tail Sheath
Tail Fiber
Surface Proteins
Membrane Envelope

18. Structures & Function
Capsid: Protein coat, allows virus to enter a cell by “tricking” the cell to allow inside. -Once inside, genes expressed and sometimes the cell makes copies of the virus or the host cell is destroyed

19. Lytic Cycle DNA replication Binds to receptors on the bacterial
cell wall.
Injects DNA into
bacteria
Cell wall broken
down by enzymes
(lyses)
Production &
assembly
of new viruses
Full assembly
of new viruses

20. Another View . . .

21. Lysogenic Cycle
Bacteria divides, prophage replicates as part of bacteria’s nucleoid
Genes injected into bacteria & become a phrophage
Prophage can exit the bacterial chromosome and enter the lytic cycle
Start of lytic cycle