Prokaryotic Structure:

1
Chapter 4

• Prokaryotic Structure
• External structures

2
Properties of life

• What are some properties that make something
  alive?
• Metabolism
• Reproduction
• Differentiation
• Evolution

3
Cells make up all living things

• What are the different types of cells?
• Prokaryotic
• Archaea and bacteria
• Eukaryotic
• plants, algae, fungi, protists, and animals
  (variety)

4
Prokaryote Eukaryote

• Absence of nucleus
• One circular chromosome, not in a membrane
• No histones
• No organelles
• Peptidoglycan cell walls(bacteria)
• Binary fission for cell division
• Smaller

• Contain nucleus
• Linear chromosomes, in nuclear membrane
• Histones protein that DNA winds around
• Membrane enclosed organelles
• Simple (polysaccharide) cell walls
• Cell division by mitosis or meiosis
• Larger

5
Different prokaryotes have different shapes
(morphology)

• Coccus(sphere)

6
Different prokaryotes have different shapes
(morphology)

• Bacillus(rods)

7
Different prokaryotes have different shapes
(morphology)

• Spiral

8
Some prokaryotes have unusual shapes

• Star-shaped Stella
• Square Haloarcula
• Most bacteria are monomorphic
• A few are pleomorphic

Figure 4.5
9
The cells are arranged in certain ways

• Pairs DiplococciChains Streptococci
• Clusters Staphylococci
• Chains Streptobacilli

Figures 4.1a, 4.1d, 4.2c
10
External Structure - Glycocalyx

• Outside cell wall
• Gelatinous, sticky substance
• A capsule is neatly organized
• A slime layer is unorganized and loose
• 3 Main functions
• Adherence - allows bacterial cell to attach to
  the host
• Streptococcus mutans and tooth decay
• Capsules prevent phagocytosis (virulence factor)
  being taken in by host and destroyed
• Protection of pathogen from host immune system
• Bacillus anthracis and Klebsiella pneumoniae
• Protection from dehydration

Figure 4.6ab
11
External Structures - Flagella

• Outside cell wall
• Long filaments that propel some prokaryotes
• Structure
• Filament Made of chains of flagellin
  responsible for the actual movement
• Attached to a protein hook
• Anchored to the wall and membrane by the basal
  body

Figure 4.8a
12

• Look at animation flagella structure

13
Flagella Arrangement
Figure 4.7
14
Flagella movement

• When flagella rotate counter clockwise, they
  bundle and create runs move towards a stimuli
• When flagella rotate clockwise, they separate and
  create tumbles change direction and move away
  from a stimuli

15

• Look at animation flagella arrangement

16
Motile Cells

• Rotate flagella (counterclockwise or clockwise)
  to run or tumble
• Move toward or away from stimuli (taxis)
  favorable or unfavorable environment
• Stimuli signals that stimulate movement
  (attractants or repellants)
• Type of stimuli
• Chemical ? chemotaxis
• Light ? phototaxis

17
Run and Tumble
Figure 4.9
18
External Structure Axial Filaments

• Endoflagella
• Move spirochetes
• Treponema pallidum (Syphilis)
• Borrelia burgdorferi (Lyme disease)
• Fibril bundles beneath a sheath anchored at one
  end of a cell
• Spiral movement
• Rotation causes cell to move

Figure 4.10a
19

• Look at animation spirochetes

20
Other External Structures

• Pilin
• Arranged helically around cell
• Mostly Gram negative
• Two types
• Fimbriae
• Found at ends or distributed evenly
• Sticky bristle-like projections
• Allow attachment or adherence to surfaces
• Neisseria gonorrhoeae attachment to mucous lining
• Pili
• Longer than fimbriae
• Straight hairlike appendages
• Used for attachment to other cells to transfer
  DNA from one cell to another
• Ex. Sex pili during conjugation

Figure 4.11
21
PILI
22
Cell Wall

• Purpose/significance
• Prevents osmotic lysis
• Cell shape
• Differentiation
• Anchor flagella
• Virulence
• More rigid and complex than eukaryotes
• Made of peptidoglycan (in bacteria)
• Sugar backbone (NAM-NAG), tetrapeptide side
  chains, peptide crossbridge

Figure 4.6a