3. Prokaryotes Flashcards
- Are prokaryotes heterotrophic or autotrophic?
- Can be both
- Heterotrophs requires preformed organic molecules for growth
- Autotroph can live exclusively on inorganic matter and an energy source
What were the ancient prokaryotes?
- Earliest was probably a chemoautotroph
- Photosynthetic species were anoxygenic
What was the early environment of the Earth like?
Hot, saline and high UV (no ozone)
When did the first oxygenic bacteria (Cyanobacteria) appear?
- Oxygenic bacteria appeared about 3.5 billion years ago
- Contain chlorophyll, photosynthetic
- Created the O2 atmosphere of today
What was the role of prokaryotes in the early environment?
- Prokaryotes transformed the ancient inorganic environment
- Atmospheric oxygen
- Organic carbon
- Nitrification where nitrogen fixers convert N2 to ammonia with nitrifers convert ammonia to nitrate
What is the membrane of archae like?
- Phospholipids are from ether linkages in Archaea compared to ester linkages in Bacteria
What are the differences between archaea and bacteria?
- Cell wall composition (bacteria have peptidoglycan)
- Bacteria membrane lipids are ester linked
- They are sensitive to toxins and antibiotics
How does the genetic exchange of bacteria occur?
- Conjugation
- Transformation
- Transduction with bacteriophage
What is the purpose of bacterial genetic exchange?
Enables transfer of genes across genera, creating an issue with spread of antibiotic resistance
What is conjugation?
Where plasmid the plasmid is transferred during conjugation
What is transformation?
Partial genome transfer by DNA uptake
What is transduction?
Transfers as part of a viral genome
What are the 2 shapes of bacterial diversity?
- Cocci
- Bacilli (rods)
- Filamentous
What is the difference between two distinct bacterial cell walls?
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.
What are mycoplasma?
- Smallest known cells with the smallest genomes
- Lack cells walls (no peptidoglycan, so penicillin resistant)
- Parasites or commensalism
- Cause of pneumonia in humans
What does diphtheria cause? Mode of infections
- 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
Which bacteria produce the diphtheria toxin?
Bacteria containing prophage Beta can produce the diphtheria toxin
What is the virus that causes tuberculosis?
Mycobacterium tuberculosis
What is the mode of transfer for mycobacterium tuberculosis?
- No toxins
- Produce mycolic acids that are hydrophobic and protect against antimicrobials, host defences, pH changes
- Inhibits the fusion between phagosome and lysosome
What causes leprosy?
Bacteria named mycobacterium leprae
What is the mechanism of infection for leprosy?
- grows in macrophages in cooler parts of the body as well as nerve and skin cells
- Schwann cell infection results in loss of sensation
What is streptomycin?
First drug effective against tuberculosis
