Flashcards in Microbial Genetics (Ian Bloomfield) Deck (141)
Are bacterial prokaryotes or eukaryotes?
What are some characteristics of prokaryotes?
- Cytoplasm does not contain membrane bound organelles
- In some bacteria the plasma membrane can form extensive folded structure that extends into cytoplasm
- Lack nucleus
- Transcription and translation occur simultaneously in the same place
How many bacterial cells are there on earth? and how many different types are there?
~ 5 x 10^30
- >10^7 different types
How much of the worlds carbon biomass is made up by bacteria?
(also, majority of nitrogen and sulfur in living material)
Approx how many bacteria have been cultured in the lab?
What are the 3 domains of life?
> Algae and plants
> Fungi and animals
What are prokaryotes and eukaryotes?
- Archaea and Bacteria
Describe the changes in earth atmosphere composition and organism changes from origin of earth to present
1) Origin of Earth (4.6bya)
2) Bacteria (~4bya)
3) Anoxygenic phototrophic bacteria (~3.5bya)
In these steps the earth is anoxic (without oxygen) (N2, CO2, CH4 atmosphere)
4) Origin of cyanobacteria (~3bya)
Earth becomes slowly oxygenated
5) Origin of eukaryotes (~2bya)
6) Algae diversity (~1.5bya)
7) Within last 0.5by, in order:
What are autotrophic cyanobacteria?
Conduct photosynthesis by splitting water and releasing oxygen
What is endosymbiosis and what is the endosymbiotic theory?
Endosymbiosis is when one partner population grows within the body of another organism
Endosymbioti theory is a theory of how eukaryotes evolved from prokaryotes
- Eukaryotes underwent one (animals) or 2 (plants) rounds to endosymbiosis
What do archaea include?
- None are pathogenic (as far as they know)
What 2 groups of bacteria do most pathogenic bacteria belong to?
Proteobacteria and Gram positive bacteria
What are the typical sizes of pro vs eu cells?
How long is a typical E.coli?
How many more bacterial cells do humans have than their own cells?
10 bacteria to 1 cell
Give some examples of the ecological importance of bacteria
- able to oxidise inorganic ions (e.g Fe2+) as a source of electrons to generate a membrane potential for ATP biosynthesis and other functions
2) Phototrophs (carry out photosynthesis)
- Autophototrophs (use CO2 like plants)
- Heterophototroph (need an organic carbon source)
- oxidise organic molecules in orfer to produce NADH needed for PMF required for ATP biosynthesis
4) Some bacteria produce cellulase - needed for utilisation of cellulose
5) Involved in nitrogen and sulfur cycles
- Fixing (generate ammonia from atmospheric NH2)
- Nitrifying (oxidise ammonia)
- Denitrifying (convert nitrate to NH2)
Give some examples of the medical importance of bacteria
Some bacteria pathogenic: important to study to prevent disease
- Robert Koch pioneered scientific study of pathogenesis
1) Mycobacterium tuberculosis causes tuberculosis (discovered by Koch)
- around 25% of worlds population infected
2) Enterobacteriaceae major cause of intestinal infections
3) MRSA world threat to human health
What is Escherichia coli and who discovered it?
- Gram negative enteric bacterium
- Discovered by Theodor Escherich
- Important model organism
What macromolecules are bacterial cells composed of?
- Murein or peptidoglycan
- Cell membrane
Proteins, DNA, RNA, lipids etc
How are these components produced?
- By polymerisation reactions in which building blocks are joined by enzymatic reactions
What are the building blocks?
Where do the building blocks come from?
1) Made de nova
2) Taken up from the environment
What are the bacterial building blocks synthesised from?
Made in biosynthetic pathways from one or more of 12 precurosr metabolites
e.g acetyl-CoA, Succinyl-CoA, pyruvate, G6P
Where do the 12 precursor metabolites come from?
Pentose phosphate pathway
e.g pyruvate from glycolysis, succinyl CoA from TCA cycle
What are the main elements missing from the precursor metabolites that are present in one or more of the building blocks?
Nitrogen and Sulfur
How do bacteria assimilate nitrogen? (incorporate nitrogen into usable organic molecules)
Using the nitrogen cycle
How does the nitrogen cycle work?
1) Nitrogen fixing bacteria
- Fix dinitrogen gas by enzyme nitrogenase to ammonium (NH4+)
2) Nitrifying bacteria
- Oxidise ammonium first to nitrites (NO2-) then to nitrates (NO3-)
3) Denitrifying bacteria
Denitrification of NO3- to N2
What is the only source of nitrogen that can be assimilated into bacterial cell constituents?
What are the 3 key enzymatic systems used in assimilation of nitrogen in E.coli?
1) L-glutamate dehydrogenase (GDH) catalyses the combination of ammonia with alpha-ketoglutarate to produce glutamate
2) Glutamate reacts with second molecule of ammonia to produce glutamine (catalysed by glutamine synthase)
3) To complete cycle, glutamine then reacts with alpha-ketoglutarate to generate 2 molecules of glutamate (catalysed by glutamate synthase)
- 1 can be used in bacteria, 1 used to bind with ammonia
(Diagram good if confusing)