I.
II.
III.
IV.
V.
SIZE, SHAPE, AND
ARRANGEMENT
CELL WALL
CELL MEMBRANE
INTERNAL STRUCTURE
EXTERNAL STRUCTURE

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All prokaryotes are classified to either the domain Arehaea (ancient bacteria) or the domain Bacteria
(true bacteria).
The two domains differences are on the molecular level, not in the structural level.
Most belong to the domain Bacteria.
Archaea has no pathogenic forms, yet!

I. SIZE, SHAPE, AND
ARRANGEMENT
A. Bacteria are generally smaller than
Eukaryotes.
B. They have a large volume to surface ratio which allows them to move substances in and out of the cell quickly.
C. The bacteria Epulopicium fishelsoni can be seen with the naked eye!

I. SIZE, SHAPE, AND
ARRANGEMENT
D. Bacteria are grouped by shape
(look at figure 4.1).
1. Coccus – round and “grape like” shape.
2. Bacillus – rodlike shape. They can be rectangular, club shaped or swollen.
3. Coccobacillus –between a coccus and bacillus.

I. SIZE, SHAPE, AND
ARRANGEMENT
4. Vibrio – spiral bacteria that has a comma shape.
5. Spirillum (Spirilla) – spiral bacteria that has a rigid wavy-shape.
6. Spirochete – sprial bacteria that has a corkscrew shape.

I. SIZE, SHAPE, AND
ARRANGEMENT
E. Bacteria can also have certain arrangements (look at figure 4.2).
1. Di = pairs
2. Tetrads = groups of 4
3. Sarcina(e) = packets of 8
4. Strepto = chains
5. Staphylo = grape like clusters
6. Star shaped, Square and
Rosette(attached to a substrate)

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II. CELL WALL
A. Most all bacteria have a cell wall
(Look at figure 4.3 and your coloring sheets). It serves two functions:
1. It helps maintain the shape of the cell.
2. It prevents the cell from bursting by osmosis.

II. CELL WALL
B.
The rigid cell wall outside the cell membrane is composed mainly of the polymer peptidoglycan (most important component in cell walls) .
C.
Cell walls differ in composition and structure. We classify them on a staining technique a called the gram stain . They can be positive or negative.

II. CELL WALL
D.
GRAM POSITIVE BACTERIA
1.
In Gram-positive bacteria, the cell wall consists of a thick, dense layer of peptidoglycan, with teichoic acid in it (Look at figure 4.6).
2. If you digest the cell wall of these bacteria they become
PROTOPLASTS (a cell that has a membrane but no cell wall). It also has a small periplasmic space (area between membrane and the cell wall).

II. CELL WALL
E.
GRAM NEGATIVE BACTERIA
1. Cell wall has a thin layer of peptidoglycan, separated from the cell membrane by the periplasmic space(larger) and enclosed by an outer membrane made of
LIPOPOLYSACCARIDE (Contains
Lipid A – Fat), or ENDOTOXIN .
2. If you digest away the cell wall they become SPHEROPLASTS (has cell membrane and most of the outer membrane.
3. Lipid A can cause fever ect…Toxic!

II. CELL WALL
F. In acid-fast bacteria , the cell wall consists mainly of lipids, some of which are true waxes, and some of which are glycolipids
.
G. Some bacteria have no cell walls.
One species is Mycoplasma and shows various shapes and forms.
H. Cell walls are controlled by
Penicillin (blocks formation of cell walls) and Lysozyme (found in tears and secretions digests peptidoglycan).

A. The cell membrane has a fluidmosaic structure with phospholipids forming a bilayer and proteins interspersed to a mosaic pattern.
B. It regulates the movement of materials into and out of cells.
C. It performs functions usually carried out by organelles of eukaryotic cells – DNA replication, respiration, captures ATP, secretes proteins .

A.
Cytoplasm - the semifluid substance inside the cell membrane. Look at coloring sheets.
B.
Ribosomes - consist of RNA and protein, serve as sites for protein synthesis.
C.
Nuclear region - usually includes just one, large, circular chromosome, which contains the prokaryotic cell's DNA and some
RNA and protein. It is also possible, but rarely, to have two circular chromosomes.

D.
Inclusions – small bodies inside the cytoplasm. There are two types:
1. Granules - store glycogen
(energy) or other substances.
2. Vesicles - filled with gas (to help them float in water).
E. Endospores – helps the organism survive in adverse conditions. May also be part of the regular life cycle. They are very resistant to heat, acid, radiation. Can live up to
10,000 years at –14C at 430m!

F.
Plasmids – smaller circular molecules of
DNA. This supplements information contained in the chromosome.
These are also used in genetic engineering.

V. EXTERNAL STRUCTURES
A. Bacteria can contain flagella & pili which extend beyond the cell wall and can have slime layers and capsules which surround the cell wall.
B.
Flagella - (Half of all bacteria are motile) long thin, hairlike projections. 5 types:
1. Monotrichous – one flagella at one end.

V. EXTERNAL STRUCTURES
2.
Amphitrichous – 2 flagella; one at each end.
3.
Lophotrichous – 2 or more at one end or both ends.
4. Peritrichous – Flagella all over the surface.
5. Atrichous – without flagella, cocci rarely have them.

V. EXTERNAL STRUCTURES
C. Structure of a Flagella (Figure
4.13)
1. Made of Protein = Flagellin
2. Basal body – embedded in the cell membrane.
3. Hook – rotates; attaches to filament; counterclockwise = moves straight; clockwise = moves in a tumble.
4. Filament – Extends from cell, causes the movement.

V. EXTERNAL STRUCTURES
D.
Axial filaments or Endoflagella - do not extend away from body; on surface; found in spirochetes; causes it to rotate like a corkscrew.
E. Much of bacterial movement is random (see figure 4.14).
F.
Chemotaxis - movement toward attractants and away from repellants.
G.
Phototaxis - movement toward or away from light.

V. EXTERNAL STRUCTURES
H.
Pili – help bacteria attach to a surface.
1. Conjugation pili - allow exchange of
DNA.
2. Attachment pili (fimbrae) - help bacteria adhere to surfaces.
I.
Glycocalyx - includes all polysaccharides external to a bacteria’s cell wall. Two types:
1. Capsules - prevent host cells from destroying a bacterium; capsules of any species of bacteria have a specific chemical composition.

V. EXTERNAL STRUCTURES
2.
Slime layers - protect bacterial cells from drying, trap nutrients, and sometimes bind cells together, as in dental plaque.