Bacteriology Intro

Question 1

Are the majority of Bacteria on earth Pathogenic?

Answer 1

No

Question 2

How many prokaryotes are there on Earth?

Answer 2

5 * 10^30

Question 3

What are some advantages to being small?

Answer 3

• Larger surface to volume ratio = good for nutrient exchange
• Grows/replicates faster(double pop in 10 min)
• 1 set of chromosomes = faster evolution

Question 4

Name the 4 phases of bacterial growth

Answer 4

Lag phase - adjusting to medium
Logarithmic growth - pop. explosion
Stationary - running out of nutrients
Death

Question 5

What are the shapes of Coccus, Rod and Spirillum?

Answer 5

Coccus = sphere
Rod = linear cylinder
Spirillium = snake / twisted rod

Question 6

Basic bacterial cell structure includes

Answer 6

Cytoplasm, nucleoid, ribosomes, plasmid, cytoplasmic membrane, cell wall, cell envelope

Question 7

How is a gram stain achieved?

Answer 7

1. Flood heat-fixed smear with crystal violet for 1 min (all cells purple)
2. Add iodine solution for 1 min (still purple)
3. Decolourize with alcohol briefly (Gram+ = purple, Gram- = colourless)
4. Counterstain with safranin for 1-2 min (Gram+ = purple, Gram- = pink)

Question 8

What is the cell wall difference between G+ and G- bacteria?

Answer 8

G+ = thick cell wall (keeps dye in)
G- = thin cell wall, outter membrane = LPS, lipid A anchors LPS to membrane.
(over-response to lipid A can lead to cytokine storm and septic shock)

Question 9

Primary functions of the cytoplasmic membrane

Answer 9

1. Permeability Barrier - prevents leakage and functions as a gateway for transport of nutrients into and out of the cell
2. Protein anchor - Site of many proteins involved in transport bioenergetics and chemotaxis
3. Energy Conservation - Site of generation and use of the proton motive force

Question 10

What is the Periplasm?

Answer 10

Located in gram- bacteria between outer and inner membrane , gel like consistency, proteins = hydrolytic enzmes , Binding proteins for transport

Question 11

The nucleoid is…

Answer 11

Not nucleus, no surrounding membrane, single circular chormosome, haploid genomes

Question 12

Plasmids are…

Answer 12

• Extrachromosomal genetic elements
• Not required for growth
• Encode for ‘fitness’ factor (i.e. antibiotic resistance)
• Can be transferred from bacteria to bacteria

Question 13

What makes a pathogen successful?

Answer 13

Colonization, invasion/toxigenicity, immune evasion, transmission

Question 14

What is a virulence factor?

Answer 14

A molecule produced by the pathogen that contributes to the disease
Surface factors: LPS, flagella (movement), Pili (attachment), capsules (protection from immune system, good vaccine candidates), surface proteins, secretion systems
Secreted: shuttled across membrane or injected into host cells, exotoxins

Question 15

What are Biofilms?

Answer 15

Higher order structures

• Bacteria attach
• develop into microcolonies
• Develop biofilm over the colonies
• Biofilm hardens and matures
• Bone marrow and heart valve infections (very hard to deal with)

Question 16

What are Endospores?

Answer 16

Only in Gram+

• Highly resistant to heat, harsh chemicals and radiation
• Dormant stage of life cycle
• Common in soil
• Critical for development of disease in most cases

Question 17

What are Exotoxins?

Answer 17

Specielized virulence factors

• Secreted from bacteria
• Some are good vaccine candidates
  includes: hemolysins, toxins that function inside host cells, extracellular enzymes, superantigens

Question 18

How do exotoxins create a systmeic disease?

Answer 18

The bacteria stays localized, but toxins released by the bacteria circulate while the bacteria continues to secrete them