1. Chapter #20 : Bacteria and Viruses
I. Bacteria
A. Classifying Prokaryotes
Prokaryote – a single-celled
organism that lacks a nucleus/major
organelles.
-All prokaryotes used to belong to
the Kingdom Monera.
-They’re now divided into 2 groups :
1. Kingdom Eubacteria – larger group that is found almost everywhere, ex : fresh water, salt water, land, inside our bodies (E.coli).
-Cell walls of Eubacteria contain the
carbohydrate peptidoglycan.

2. Kingdom Archaebacteria
2. Kingdom Archaebacteria - bacteria that live in harsh environments & are chemically different from Eubacteria.
-Lack peptidoglycan & have
different membrane lipids.
*Archaebacteria have DNA
sequences that are similar
To Eukaryotic organisms
(are thought to be ancestors
of Eukaryotes).

3. 3 Types of Archaebacteria :
1. Methanogens – prokaryotes that produce methane gas & live in oxygen-free environments, ex : human gut & thick mud in swamps.
Aerobe – bacteria that require
oxygen for survival.
Anaerobe – bacteria that live in
oxygen-free environments (oxygen
is a poison to them).
2. Thermophiles – live in extremely hot environments : “therm” = heat, ex : hot springs & undersea vents.
3. Halophiles – live in extremely salty environments, ex : Salt Lake & the Dead Sea.

4. B. Identifying Prokaryotes
*Prokaryotes are identified by :
1. Shape.
2. Chemical nature of their cell walls.
3. The way they move.
4. The way they obtain energy.

5. Shape - 3 basic bacterial shapes :
A. Bacilli – rod-shaped prokaryotes.
B. Cocci – spherical or
circular prokaryotes.
C. Spirilla – spiral or corkscrew- shaped prokaryotes.

6. Shape - 3 basic bacterial shapes :
Other shapes :
a. Strepto – chains of
bacteria.
b. Staphylo – grape-like
clusters of bacteria.
c. Diplo – 2 bacteria
together.
d. Mono – 1 bacterium.

7. Cell Walls - 2 Types in Eubacteria :
*The method of Gram-staining is used to tell them
apart.
In Gram staining :
1. 2 dyes are applied to bacteria.
a. Violet stain – primary stain.
b. Red stain – counter stain.
2. Violet stain is applied first & stains peptidoglycan cell walls.
3. Alcohol is applied & if bacteria stay violet it is
Gram-positive.
4. If bacteria are Gram-negative they have thin walls
& an outer lipid layer. Alcohol dissolves lipids &
counter stain dyes them red/pink.

8. Gram Staining
Gram positive
Gram negative

9. Movement – Structures used & types :
Flagella – whip-like
structures used for
movement.
Other ways to move :
lash, snake, spiral
forward, or glide along
a layer of slime-like
material they secrete.

10. Basic Bacterial Structure

11. Basic Bacterial Structure

12. Chloroplast

13. The Importance of Bacteria
Bacteria impact living organisms on a daily basis. How are they good? How are they bad?