Why are Microbes Ruling the World?

Question 1

What is the importance of studying microbes and viruses?

Answer 1

• They make up the majority of the 3 domains
• Tiny & single-celled
• Most genomes sequenced
• All known biodiversity is microbial

Question 2

What is antibiotic resistance?

Answer 2

• seen for nearly all antibiotics developed

Question 3

What is a mega plate?

Answer 3

A simple and more realistic platform to explore the interplay between space and evolutionary challenges that fore organisms to change or die

Question 4

What is transformation?

Answer 4

Where bacterium takes up free DNA from environment

Question 5

What is transduction?

Answer 5

• Where bacterial viruses take DNA from one bacterium to another
• not all bacteria can do this
• recipient bacteria must be in a state of competence
• homologous recombination (replacement) or integration of new material
• response to poor environmental conditions and agents that cause DNA damage
• plasmids can also transform
• bacteria can take up antibiotic resistant gene from another species and incorporate it into their own DNA

Question 6

What is conjugation?

Answer 6

The direct transfer of DNA from one bacterium to another

Question 7

What is epistasis?

Answer 7

Where repairing one mutation will only be slightly more beneficial for the organism, but repairing all mutations will result in an exponential increase in benefit

Broken car example

• repairing the engine only will have it go 5 km/h
• repairing the flat tire only will have it go only 10km/h
• repairing both problems will allow the car to go 100km/h

Question 8

Describe what compensatory mutations are

Answer 8

When a change in one gene makes thing worse but is followed by another change in a gene which helps to fix things

Question 9

Talk about the role of space, time and geography in evolution of antibiotic resistance on mega plates

Answer 9

• within about 25 generations of reaching first antibiotic, a colony had evolved resistance
• about 720 generations were resistant to the strongest antibiotic (1000x)
• the most frequently mutated gene was the primary target of the specific antibiotic used
• mutations that increased resistance often came with a cost of reduced growth
• subsequently restored by later compensatory mutations
• almost all also had a mutation in the POL 3 gene
• DNA replication proofreading which leads to increased mutation rates

Question 10

What are the features of microbes that contribute to rapid evolution?

Answer 10

• Smaller genomes
• Shorter generation time
• ROS induced mutations
• Stress

Question 11

What is the role of antibiotic use in selection for antibiotic resistance?

Answer 11

To eliminate bacteria that does not have the target genes

Question 12

What is the role of stressors (e.g. ROS) in the development of antibiotic resistance?

Answer 12

• antibiotics boost bacterial production of free-radical oxygen molecules
• damage bacterial DNA
• induce widespread mutations
• more chances to randomly acquire drug-resistant traits

Question 13

What is the role of microbial DNA in human disease?

Answer 13

• bacterial DNA sequence are in about a third of healthy human genomes via recent viral integration
• present in a far greater percentage of cancer cells than healthy cells
• insertions may disrupt tumor suppressor genes

Question 14

What are the possible roles of microbial genes in animal genomes?

Answer 14

• in about 145 functioning genes likely arose from HGT into animals from simpler organisms