1. CH 4 PROCARYOTES: BACTERIA & ARCHAEA (“ARCHEAH”)
First cells were a type of archaea that were possibly related to modern ones that live on sulfur compounds in geothermal ocean vents—very adaptable cell structures
Under light microscopes bacteria appear simple and w/o features—electron scopes in the 40’s—50’s proved otherwise
Found that bacteria had : appendages (flagella, pili, fimbria)
Layers to their cell coverings (glycocalyx, cell wall, cell membranes)
Objects (NOT organelles!) in their cytoplasm (ribosomes, granules, nucleiod, chromosome)

2. Bacterial Shapes, Arrangements & Sizes
Even if found with another cell, each bacterial cell is independent and capable of carrying out all life processes
SHAPES—determined by the cell wall
Coccus (cocci)—spherical, ball shaped, but can also be bean shaped, oval or “pointy”
Bacillus (bacilli)—cylindrical, rod shaped, many variations according to species
Spirillum/spirochete—spiral shaped cylinder, 3 types:
Spirillum– rigid, corkscrew
Spirochete– flexible, spring-like
Vibrio– comma shaped cylinder

3. Pleomorphism
Same species varying in shape and size due to variations in cell wall caused by nutritional or hereditary differences
Corynebacterium diphtheriae are rod shaped, but can also be club shaped, swollen, curved, filamentous or round
Mycoplasmas lack cell walls, so have extreme shape variations

4. Arrangements
Bacteria can be arranged several ways (fig 4.25) determined by how the cells divide
Coccus can be in pairs: diplo
Chains : strepto
Tetrad: sarcina
Irreg. clusters: staphylo
Bacillus can be pairs or chains
Palisades: diplobacillus that snap at hinge and fold back on each other
Spirilla normally do not remain attached after division
See fig 4.26 for size comparison

5. Appendages Common, but not in all species 2 major groups:
Motility: flagella
For attachment: fimbria and pili
FLAGELLA– self-propulsion, made of 3 distinct parts
Filament—helical structure composed of proteins, 20 nm in diameter, 1-70 nm in length
Hook—curved and tubular, holds the filament, anchored to the cell by the…
Basal body—stack of rings that go thru the cell wall to the cell membrane
This arrangement allows the hook and filament to rotate 360° in a counter clockwise motion, which moves the bacteria forward
Appendages

6. Flagella, cont.
Arranged in 3 ways: polar—flagella attached at 1 or both ends
Monotrichous—single flagellum
Lophotrichous—small bunches of flagella at same site
Amphitrichous—flagella at both ends
Second arrangement: peritrichous where the flagella are randomly dispersed over the entire cell
Periplasmic flagella are those found in the space between the cell wall and cell membrane and causes the cell to wiggle, twist and flex (spirochetes)
Can determine motility by:
Put sample INSIDE semisolid media—rapid growth thru entire medium indicates motility
Observe using a hanging drop slide (fig 4.4)

7. Bacteria with flagella are sensitive to their environment
Positive chemotaxis—movement toward a favorable chemical stimulus (food)
Negative chemotaxis—movement away from a repellant compound
Phototaxis—movement in response to light

8. Appendages for Attachment & Mating
Pilus and fimbria provide adhesion, but not locomotion
Fimbria are shorter and more numerous strands
Pilus are longer and sparser
Some pathogens use fimbria to adhere to epithelial cells to cause disease:
Gonococcus—gonorrhea in genitourinary tract
E. coli—intestinal tract
Sex pilus is a special tubular structure made of pilin (protein) used in bacterial conjugation: partial transfer of DNA thru this cytoplasmic connection—only occurs between Gram neg. cells
Conjugation does occur between Gram pos. cells, but not with a sex pilus