Three Domain Classification
EU
PROKARYOTES

Prokaryotic Cells Eukaryotic Cells
Genetic Material DNA not bound by membrane; DNA usually a singularly circular chromosome
Organelles Lacks membranebound organelles
Cell Wall
Cell Division
Cell walls contain peptidoglycan
Usually Binary
Fission
DNA found in a nucleus; DNA contained in multiple chromosomes
Contains membrane-bound organelles
Cell walls are usually chemically simple
Mitosis


First formed about 3.5 billion years ago

FIRST LIFE FORMS WERE Archaea, or ancient bacteria

Eubacteria is true bacteria
(Eu = true)
 Eukaryote = true nucleus

• Primitive bacteria
• Live in extreme or harsh environments
• 3 kinds:
– Halophiles = live in very basic or salty environments
• Great Salt Lake
• Dead Sea
– Methanogens = don’t require O
2 methane gas (CH
4 to live, make
) as product of respiration
– Thermophiles = live in hot or acidic environments (~pH 1-4)
• Near undersea volcanic vents
• Sulphur Springs
• Hot springs in Yellowstone National Park

 Ubiquitous = they exist everywhere
 Harmful – pathogenic (they cause disease)
 Helpful – they have a variety of uses

• Food & Drink Production
– Fermentation (drinks)
– Baking (Baker’s yeast)
• Sewage Decomposition
– Bacteria break down the organic matter
• Nitrogen Fixation in roots
– Helps plants take up H
2
O and nutrients from soil

• Mining
– Bacteria concentrate desired elements from ore
• Bioremediation
– Microbes can help repair damaged ecosystems
• Human Recreation = Artificial Snow-Making
– Bacteria allow H
2
O to form ice crystals

1.
Shape and Groupings
2.
Cell wall composition
3.
Environment
4.
DNA Sequences


Bacterial Structure
Cell Wall


Prevents cell from rupturing
Composition of cell wall helps to identify bacteria

Cell Membrane


F(x) = support & protect
Differentially permeable

Cytoplasm

Contains organelles (non-membranous)

Bacterial Structure

Genetic Material

Single, circular chromosome

Plasmid = extra chromosome that can replicate separately from the main chromosome
•
•
Can be used as a vector for biological engineering
Can pass genes for antibiotic resistance onto other bacteria (sometimes resistance to several antibiotics @ one time)



Bacterial Structure
Ribosomes

F(x) is to synthesize proteins
Capsule (Slime Layer)



A viscous coating on the outside of a bacteria
Exterior to the cell wall
F(x)s:
•
Protection
•
•
Increases a bacteria’s pathogenicity (or ability to cause disease)
Protects bacteria from the Immune System
(WBC’s)


Bacterial Structure
Other structures (Appendages)

Flagella (protein appendage)
•
•
F(x) = locomotion
Cell can have one, two, or many

Pili (hair-like extensions)
•
F(x)s = attachment to host and transfer of genetic material

Fimbrae (shorter than pili)
•
F(x) = adhesion to surfaces


Typical

Coccus/Cocci = spherical or round

Bacillus/Bacilli = rod-shaped

Spirillum/Spirilli = spiral-shaped

Spirochete = helical-shaped

Vibrio/Vibrios = curved rod

Coccobacillus = very short rod

 Atypical
 Pleiomorphic = vary in size and shape
 Star-shaped
 Rectangular or Cube-shaped
 Mycoplasms = can change shape
 Lack a rigid cell wall
 Have a strong cell membrane



– 1 plane =
• diplo(pair)
• strepto(chain)
– 2 planes =
• tetrad (packet of 4)
– Several planes @ random =
• staphylo-
(grape-like clusters)

• History & Definitions
– Developed by Hans Christian
Gram in 1884
– Used to help identify different typ es of bacteria (a differential stain)
– Stain uses differences in cell wall composition to differentiate between bacteria
– The most common/popular method for staining bacteria
– Can help determine which type of antibiotics will be most effective against a particular bacteria

• Stain purple
• Contain:
– A thick peptidoglycan layer + teichoic acids (cell wall)
– Sits on top of the plasma membrane
– This layer is permeable to small molecules
• More susceptible to Penicillin

• Stain pink/light red
• Contain (triple layer):
– A outer layer of lipopolysaccharides + outer membrane
(space)
– A thin layer of peptidoglycan
(space)
– A cell membrane
– Porin proteins in the outer membrane allow larger molecules to pass
• Less susceptible to Penicllin

Outer Layer
Cell Wall
Cell Membrane

• Antibiotic that inhibits the synthesis of peptidoglycan; used on actively growing organisms.
– Gram (+) cells  Penicillin can get to the peptidoglycan layers
– Gram (-) cells  Pencillin has a harder time attacking the peptidoglycan layers
– Some Penicillin derivatives can pass through the porin proteins of Gram (-) cells

•To better view a cell’s structure.

Steps (abbreviated):
1) Add primary (1 o ) stain – Crystal Violet
2) Add mordant to cells – Iodine
3) Add decolorizer to cells – Alcohol
4) Add secondary (2 o ) stain - Safranin