2. Bacteria and Viruses
Prokaryotes: single cell organism that lacks a nucleus
Divided into two groups, or domains, which are above kingdoms
Eubacteria and Archaebacteria

3. Archaebacteria
Live in extremely harsh environments
Where there is no oxygen (in intestine)
Where extremely hot (hot springs)
Where it is extremely salty (Great Salt Lake)
DNA in genes resembles eukaryotes

4. Eubacteria Eubacteria
Larger of the two groups; most numerous organisms on earth
Oldest forms of life on Earth
Varied in shape and color
Live almost everywhere
Each bacterial cell performs the same basic functions that complex organisms perform

5. Structure of Bacteria Bacilli Cocci Spirilla Lacks a nucleus
Has a cell wall that is tough rigid to support, shape, and protect the cell
Shapes
Bacilli – rod shaped
Cocci – spherical
Spirilla – spiral and corkscrew-shaped
Movement: some use flagella but most do not move
Bacilli
Cocci
Spirilla

6. How bacteria obtain energy
Most are heterotrophs
Feed on living organisms (parasitic)
Eat other organisms
Eat dead things
Some are autotrophs
Use sunlight to produce food
Some are chemoautotrophs
Can use energy in sulfur, ammonia, nitrites, or iron to make food

7. Growth and reproduction
Under favorable conditions, undergoes binary fission
Two new daughter cells are formed
Asexual reproduction

8. Bacteria in nature Decomposers: recycle nutrients
Nitrogen fixers: live on roots of plants and change nitrogen gas (N2) to ammonia (NH3)
Pathogens: Cause disease such as food poisoning
Human use: produce variety of food; helpful in cleaning environment
How Control Bacteria
Sterilization with heat or chemicals (bleach solution)

9. Size Comparison

10. Viruses
Characteristic of a virus
Not a cell so can’t perform all the functions of a living cell
Requires a host to reproduce therefore is a parasite—an organism that survives by living on or in a host
All kingdoms are affected by viruses
Each type of virus can only infect a few specific kinds of cells

11. Structure of Viruses
Structure of virus
Core of hereditary material – either DNA or RNA
Outer protein coat to protect virus from environment
Can only be seen with an electron microscope
Can have many shapes

12. Reproduction of Viruses
Attaches to a cell
Injects hereditary material into living cell
Cell begins to produce new virus particles

13. Two types of infection
In lytic infection, virus will cause cell to burst and virus particles will leave the original host cell
In lysogenic infection, virus genetic material becomes part of the host DNA and is copied, or replicated, along with the host DNA