Download Bacteria - Part One

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.
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 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.
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.
Shape - 3 basic bacterial shapes :
A. Bacilli – rod-shaped
prokaryotes.
B. Cocci – spherical or
circular prokaryotes.
C. Spirilla – spiral or
corkscrew- shaped prokaryotes.
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.
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.
Gram Staining
Gram positive
Gram negative
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.
Basic Bacterial Structure
Basic Bacterial Structure
Chloroplast
The Importance of Bacteria
Bacteria impact living organisms
on a daily basis.
How are they good?
How are they bad?