1-2: A Diverse World of Microbes

Question 1

What relates bacteria and arachaea

Answer 1

they are prokaryotes

Question 2

What are viruses, how do they differ from microbes

Answer 2

Genetic elements (DNA, RNA) that can multiply within a cell
Fundamentally different from microbes
Obligate parasites, NOT CELLS
Lack hallmarks of cells (metabolism, ribosome)

Question 3

What is LUCA

Answer 3

Last universal common ancestor (between P,A,E)

Question 4

When did bacteria separate from E and A? When did E and A separate?

Answer 4

3.5 bya, 2 bya

Question 5

What is the RNA world hypothesis?

Answer 5

Nucleotides assembled using template directed non-enzymatic replication. This lead to improved replication, simple functions (stability, molecule binding) and eventually enzymes

Question 6

Describe some evidence of the RNA world hypothesis (4)

Answer 6

RNA can form stable structures that can bind many molecules and carry out chemical reactions
Proteins are still made using RNA (tRNA, catalytic RNA in ribosomes)
Variety of universal biological molecules (ATP, NADH, FAD, CoA, SAM)
Various ribizymes, riboswitches, ribosomes

Question 7

Features of LUCA?

Answer 7

DNA replication, transcription, translation
Cell division
ATP as energy intermediate
Lipid bilayer membrane
Anaerobic metabolism (no O2)

Question 8

What is some evidence for LUCA?

Answer 8

There are a limited number of genes (eg. ribosomal RNA) found in all living organisms

Question 9

What are chemotrophs vs phototrophs

Answer 9

Chemo: energy from released bond E from chemical compounds
Photo: absorb light, transform to chemical energy

Question 10

What is anoxic

Answer 10

When the atmosphere was devoid of oxygen (first 2 billion years)

Question 11

What changed to lead to the rise of atmospheric O2

Answer 11

Rise of photosynthetic bacteria (cyanobacteria) that produce oxygen as waste product using oxygenic photosynthesis

Question 12

What does the ozone layer do

Answer 12

Protects against UV (damages DNA), makes planet habitable

Question 13

What makes O2 special, what kind of organism did it give rise to

Answer 13

Great electron acceptor
Rise to aerobic organisms (efficient E production) and complexity

Question 14

What is the endosymbiotic theory

Answer 14

Evolution of eukarya was archaea-like ancestor engulfing an aerobic respiring bacterium (Alphaproteobacteria) which becomes an organelle, leading to gene transfer

Question 15

What is an endosymbiont

Answer 15

Organism living within another organism

Question 16

How did plants emerge

Answer 16

Engulfed photosynthetic bacterium (cyano) = chloroplast

Question 17

What are the two versions of the endosymbiotic theory

Answer 17

Serial endosymbiosis hypothesis (engulfed post-nucleus formation)
Symbiogenesis hypothesis (engulfed prior to nucleus formation)

Question 18

Give some evidence for symbiosis

Answer 18

Mitochondria and chloroplasts:
- have their own genes, ribosomes and tRNA
- Machinery is baterial
- Sequence comparisons - mitochondria related to alphaproteobacteria, chloroplasts related to cyanobacteria

Question 19

Eukaryotic DNA replication, transcription and translation machinery is more similar to archaea or bacteria?

Answer 19

Archaea

Question 20

How many microbes are there for every animal

Answer 20

~50,000,000,000

Question 21

What drives evolution and diversity in microbes

Answer 21

Competition

Question 22

What threatens the progress of combating microbial diseases

Answer 22

Antibiotic resistance on the rise

Question 23

Name six ways we use microbes

Answer 23

Wastewater treatment
Bioremediation
Biofilms
Biotech
Fermentation
Biofuels

Question 24

How many microbial cells do human bodies have?

Answer 24

The same number as human cells - they inhabit skin, mouths and GI tract