L-28

Question 1

Why are prokaryotes so dominant on earth?

Answer 1

• fast growth rate ( 13 min doubling time)

- therefore evolve and adapt fast

Question 2

What is the process by which prokaryotes reproduce asexually?

Answer 2

Binary fission

Question 3

How long were prokaryotes the sole inhabitants of earth?

Answer 3

1.7 billion years

Question 4

What are the two stages of microbial growth in a closed batch culture system?

Answer 4

Feast and famine

Question 5

What phases are a part of the feast stage

Answer 5

• lag

- exponential growth

Question 6

What does the length of the lag phase depend on?

Answer 6

• history of the inoculum

- time required to get bio synthetic reactions running

Question 7

What is happening in the exponential phase?

Answer 7

• cells are actively dividing
• nothing is limiting for growth
• population is doubling at a constant time interval

Question 8

What happens during the stationary phase of microbial growth in a closed batch culture system?

Answer 8

• cryptic growth

Question 9

What is cryptic growth?

Answer 9

• When organisms survive by consuming lysed cell constituents of other dead cells within the culture
• dynamic population with equilibrium between growing and dying cells

Question 10

What is occurring during the death phase of microbial growth in a closed batch culture system?

Answer 10

Equilibrium shifts so more cells are dying than growing

Question 11

What are the necessities for prokaryotic multiplication?

Answer 11

• carbon source (building blocks for macromolecular synthesis)
• energy source ( electrons to drive anabolic and catabolic reactions in the cell)
• reducing power (carriers of energy/electrons like NAD+ and NADP+)

Question 12

What are the 4 tropic groups in microbiology?

Answer 12

• photoautotrophs
• chemoautotrophs
• photoheterotrophs
• chemoheterotrophs

Question 13

What is a photoautotroph?

Answer 13

Organism that uses CO2 as a carbon source and light as an energy source

Question 14

What is a chemoautotroph?

Answer 14

Organism that uses CO2 as a carbon source and chemical compounds as an energy source

Question 15

What is a Photoheterotroph?

Answer 15

Organism that uses organic compounds as a carbon source and light as an energy source

Question 16

What is a chemoheterotroph?

Answer 16

Organism that uses organic compounds as a carbon source and chemical compounds as an energy source

Question 17

What is an auxotroph?

Answer 17

An organism that is unable to synthesise one or more essential growth factors and will not grow unless these factors are provided

Question 18

What percentage of all microorganisms sequenced so far lack essential pathways or key genes for the synthesis of amino acids?

Answer 18

98%

Question 19

What do auxotrophs rely on so they can survive in the wild?

Answer 19

Cross feeding (syntrophy)

Question 20

What is syntrophy?

Answer 20

When one species gains the metabolic products of another species

Question 21

What is a microbiome?

Answer 21

The complete collection of microorganisms, and their genes, within a particular environment

Question 22

What is microbiota?

Answer 22

Individual microbial species in a biome such as bacteria, fungi, archaea, and viruses

Question 23

What are the two ways we can study the microbiome?

Answer 23

• culture dependant

- culture independent

Question 24

How do culture dependant methods of studying the biome work?

Answer 24

• relies on culturing microbes in the lab

- uses pure cultures or simple enrichments

Question 25

What are the pros of culture dependant methods of studying the microbiome? (3)

Answer 25

• allows access to phenotype
• can study one organism at a time
• can manipulate conditions to see the response of the organism

Question 26

What are the cons of culture dependant methods of studying the microbiome? (4)

Answer 26

• not all organisms can be cultured
• there are too many species to grow them all individually
• requires precise conditions
• does not match real world conditions

Question 27

How do culture independant methods of studying the microbiome work?

Answer 27

• relies predominantly on nucleic acid based methods, no culturing required
• uses sequencing or metabolic profiling to study all microbes in a sample

Question 28

What are the pros of culture independant methods of studying the microbiome?

Answer 28

• allows access to genotype
• can study many organisms at a time
• shows communities as they are in nature
• can target non-culturable organisms
• provides access to unknown information/ species

Question 29

What are the cons of culture independant methods of studying the microbiome?

Answer 29

• no pure culture, so no ability to manipulate

- expensive and complex methods