3. Prokaryotes

Question 1

• Are prokaryotes heterotrophic or autotrophic?

Answer 1

• Can be both
• Heterotrophs requires preformed organic molecules for growth
• Autotroph can live exclusively on inorganic matter and an energy source

Question 2

What were the ancient prokaryotes?

Answer 2

• Earliest was probably a chemoautotroph

- Photosynthetic species were anoxygenic

Question 3

What was the early environment of the Earth like?

Answer 3

Hot, saline and high UV (no ozone)

Question 4

When did the first oxygenic bacteria (Cyanobacteria) appear?

Answer 4

• Oxygenic bacteria appeared about 3.5 billion years ago
• Contain chlorophyll, photosynthetic
• Created the O2 atmosphere of today

Question 5

What was the role of prokaryotes in the early environment?

Answer 5

• Prokaryotes transformed the ancient inorganic environment
• Atmospheric oxygen
• Organic carbon
• Nitrification where nitrogen fixers convert N2 to ammonia with nitrifers convert ammonia to nitrate

Question 6

What is the membrane of archae like?

Answer 6

• Phospholipids are from ether linkages in Archaea compared to ester linkages in Bacteria

Question 7

What are the differences between archaea and bacteria?

Answer 7

• Cell wall composition (bacteria have peptidoglycan)
• Bacteria membrane lipids are ester linked
• They are sensitive to toxins and antibiotics

Question 8

How does the genetic exchange of bacteria occur?

Answer 8

• Conjugation
• Transformation
• Transduction with bacteriophage

Question 9

What is the purpose of bacterial genetic exchange?

Answer 9

Enables transfer of genes across genera, creating an issue with spread of antibiotic resistance

Question 10

What is conjugation?

Answer 10

Where plasmid the plasmid is transferred during conjugation

Question 11

What is transformation?

Answer 11

Partial genome transfer by DNA uptake

Question 12

What is transduction?

Answer 12

Transfers as part of a viral genome

Question 13

What are the 2 shapes of bacterial diversity?

Answer 13

• Cocci
• Bacilli (rods)
• Filamentous

Question 14

What is the difference between two distinct bacterial cell walls?

Answer 14

Gram-positive bacteria have a very thick cell wall made of a protein called peptidoglycan.

Gram-negative bacteria have a very thin peptidoglycan layer that is sandwiched between an inner cell membrane and a bacterial outer membrane.

Question 15

What are mycoplasma?

Answer 15

• Smallest known cells with the smallest genomes
• Lack cells walls (no peptidoglycan, so penicillin resistant)
• Parasites or commensalism
• Cause of pneumonia in humans

Question 16

What does diphtheria cause? Mode of infections

Answer 16

• Infection leads to inflammation and formation of a pseudomembrane on the pharynx
• Membrane comprises dead host cells and the bacterium
• Exotoxin is disseminated in the blood stream where it can cause damage to the heart, kidneys or nervous system
• Toxin inhibits protein synthesis
• Symptoms are upper respiratory tract leading to paralysis and death

Question 17

Which bacteria produce the diphtheria toxin?

Answer 17

Bacteria containing prophage Beta can produce the diphtheria toxin

Question 18

What is the virus that causes tuberculosis?

Answer 18

Mycobacterium tuberculosis

Question 19

What is the mode of transfer for mycobacterium tuberculosis?

Answer 19

• No toxins
• Produce mycolic acids that are hydrophobic and protect against antimicrobials, host defences, pH changes
• Inhibits the fusion between phagosome and lysosome

Question 20

What causes leprosy?

Answer 20

Bacteria named mycobacterium leprae

Question 21

What is the mechanism of infection for leprosy?

Answer 21

• grows in macrophages in cooler parts of the body as well as nerve and skin cells
• Schwann cell infection results in loss of sensation

Question 22

What is streptomycin?

Answer 22

First drug effective against tuberculosis