Bacteriology-Prokaryotic Cell

Question 1

What range can bacteria sizes be?

Answer 1

1micrometer=0.001 mm to 1mm maximum

Question 2

What do you call spherical shaped bacteria? give 3 examples

Answer 2

Cocci: coccus,

• diplococcus
• chain of cocci
• cluster of cocci

Question 3

Bacillus describes what type of shape in bacteria?

Answer 3

Rod shape, also includes:

• Diplobacillus
• streptobacillus(chain)

Question 4

Name 3 types of shapes found in bacteria except for Bacillus and Cocci

Answer 4

1,Intermediary shape (coccibacillus)

2. Spiral shape
3. Filamentous Bacteria

Question 5

What are the main differences between Prokaryotic and Eukaryotic cell?

Answer 5

1. Prokaryotes are smaller(1-2 micrometers)
2. No internal compartments
3. Naked circular DNA + Plasmids
4. diferent genome sizes(less)

Question 6

What is the fluid mosaic model

Answer 6

-The plasma membrane is composed of a phospholipid bilayer, membrane proteins, glycolipids, small amounts of carbohydrates arranged in a mosiac pattern causing the membrane to move fluidly

Question 7

What is the 5 main functions of the Plasma membrane?

Answer 7

1. Protection of intracellular space
2. Selective permeability
3. Site for energy production
4. site for synthesis of membrane lipids and cell wall constituents
5. Distribution of the genetic material in each daughter cell

Question 8

What is the bacteria cell wall composed of? How does this relate to gram +/- bacteria?

Answer 8

Cell wall =peptidoglycan (Carbohydrate + Peptide)
G.P= Peptidoglycan has pentaglycine cross links
G.N= Peptidoglycan have direct cross links

Question 9

What is the main difference between gram positive/negative bacteria?

Answer 9

G.P= LESS COMPLEX, stains deep blue/violet
G.N= MORE COMPLEX. extra layer of lipopolysaccharides and larger periplasmic space, results in no colour for gram staining and pink for safranin

Question 10

Name 3 functions of Bacterial Cell Wall

Answer 10

1. maintains rigidity + shape
2. protects cell from osmotic lysis
3. Contributes to the pathogenicity of certain bacterial species

Question 11

where is the presence of peptidoglycans in the cell wall absent of bacteria?

Answer 11

Archaea, Mollicutes

Question 12

give examples of metabolic reserves in the bacterial cell

Answer 12

• Carboxysomes : carbon polymers. Energy and carbon source.
• Poly-β hydroxybutyrate granules : energy and carbon source
• Polyphosphates granules : source of phosphates for nucleic acid
  synthesis (or phospholipids, or energy)
• Glycogen : energy and carbon source
• Sulfur globules : Energy source. chimio-lithotrophic bacteria

Question 13

Bacterial chromosome:

Answer 13

Usually single, circular molecule of double-stranded DNA

• From 160kb to 12.000 kb. (E.coli : 4600kb)
• Self-replicating (replicon)
• Essential for survival

Question 14

Vertical transfer:

Answer 14

parent to daughter cells

Question 15

Horizontal gene transfer

Answer 15

1. Transduction
2. Conjugation
3. Transformation

Question 16

Transposons

Answer 16

One type of mobile genetic elements : transposable elements or
transposons (« jumping genes »)
 Can carry genes encoding antibiotic resistance
 Genetic instability and mutagenesis
Used in genetic engineering

Question 17

Capsules

Answer 17

Viscous material (polysaccharides, sometimes proteins) that covers the outer
layers of the cell, but also to the pili and fimbriae

Question 18

What are the functions of of the capsules?

Answer 18

resistance to host defenses (phagocytosis, complement mediated lysis)
- prevents desiccation
- some vaccines are based on capsular polysaccharides (anti-capsular antibodies)
(S.pneumoniae, N.meningitidis, H.influenzae)

Question 19

Common pili (fimbriae)

Answer 19

Involved in biofilm formation (attachment to surfaces)

• Attachement to host cells (virulence factor)
• Prevent phagocytosis (virulence factor)

Question 20

Flagella

Answer 20

Long, thin helical filament fixed to the cell at one end 
- Made of flagellin (protein)
- Gram + and Gram – bacteria
- Motility (chemotaxis : nutrients, 
other chemoattractants)

Question 21

What is an endospore?

Answer 21

Some bacteria, when facing unfavorable environmental conditions,
sporulate.
- Can resist to extreme environmental conditions (heat, desiccation,
lack of nutrient,…) for a long time
- No metabolic activity
- Consists of several characteristic envelopes: