3. Prokaryotes

Question 1

What are the prokaryotic features

Answer 1

• lack a membrane bound nucleus, organelles and cytoskeleton
• different cell walls (peptidoglycan)
• different rRNA sequences (therefore different ribosomes)
• may be heterotrophic or autotrophic

Question 2

Heterotroph

Answer 2

requires pre-formed organic molecules for growth

Question 3

Autotroph

Answer 3

Can exclusively on inorganic matter + an energy source

Question 4

Earliest prokaryote?

Answer 4

Chemoautotroph

Question 5

What was the environment like when first prokaryote emerged?

Answer 5

• hot
• saline
• high UV (no ozone)

Question 6

what are cyanobacteria and when did they emerge?

Answer 6

• oxygenic bacteria
• contain chlorophyll, photosynthetic
• created the o2 atmosphere

called cyanobacteria and appeared 3.5 billion years ago

Question 7

What is nitrification?

Answer 7

Nitrogen fixers convert N2 to ammonia while nitrifers convert ammonia to nitrate

Question 8

Saprophytes

Answer 8

a plant, fungus or micro-organism that lives on dead or decaying organic matter

Question 9

What is unique about the membranes of archaea?

Answer 9

• Phospholipids are from ether linkages in Archaea vs ester linkages in Bacteria

Question 10

What are the differences between bacteria and Archaea?

Answer 10

Bacteria has:
• cell wall composition (most have peptidoglycan)
• membrane lipids (ester linked)
• sensitivity to toxins and antibiotics
• some noted pathogens and model organisms

Question 11

Bacterial reproduction

Answer 11

• asexual

* some species produce spores

Question 12

Steps in genetic exchange between bacteria

Answer 12

• conjugation - partial genome transfer
• transformation - partial genome transfer by DNA uptake
• transduction with bacteriophage
• enables transfer of genes across genera - issue with spread of antibiotic resistance

Question 13

3 main shapes of bacteria

Answer 13

• cocci - round
• bacilli - rods
• filamentous

Question 14

Gram negative and positive

Answer 14

Gram-positive bacteria
• have a very thick cell wall made of a protein called peptidoglycan.
• blue/purple stain

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

Question 15

What are mycoplasma?

Answer 15

• smallest known cells
• smallest genomes
• lack cell walls (no peptidoglycan (so penicillin/antibiotic resistant)
• parasites
• cause of pneumonia in humans

Question 16

What is the damage-response framework

Answer 16

• interaction between host and microbe

* suggests that the host’s response to a microbe governs the outcome of the interaction

Question 17

how does toxin synthesis cause damage to the host?

Answer 17

• Bacterium is not where most damage is caused

* it releases toxins which may enter the bloodstream and then the CNS

Question 18

Virulence properties of mycobacterium tuberculosis

Answer 18

• no toxins
• slow growing - division once a day
• disease is slow to progress - takes weeks for symptoms
• may enter latent state
• does produce mycolic acids that are hydrophobic and protect against antimicrobials, host defenses, pH changes etc
• inhibits the fusion between phagosome and lysosome
• antibacterial treatment lasts nine months

Question 19

What are the effects of diphtheria?

Answer 19

• infection leads to inflammation and formation of a pseudomembrane on the pharynx
• exotoxin is disseminated in the blood stream where it can cause damage to the heart, kidney or nervous system
• toxin inhibits protein synthesis
• symptoms are upper respiratory tract>paralysis>death

Question 20

What causes diphtheria and what is it?

Answer 20

A highly contagious respiratory disease caused by corynebacterium diphtheriae

Question 21

What is streptomycin?

Answer 21

The first drug effective against tuberculosis

Question 22

What causes tuberculosis?

Answer 22

Mycobacterium - free-living saprophytes