Microbial Population

Question 1

Why are prokaryotes so dominant?

Answer 1

Fast growth rate (10mins doubling time)
Evolve/adapt fast
Over 3.5 Billion years have colonised all of our ecosystem resulting in extreme ecological and metabolic diversity

Question 2

What is binary fission?

Answer 2

Prokaryotes reproduce asexually by cell division through the process of binary fission
Binary fission results in formation of two cells that are genetically identical (clones)

Question 3

What does close batch culture system mean?

Answer 3

Refers to a form of cell culturing
Defined supply of nutrients is provided
Once used cells cannot proliferate

Question 4

What is the lag phase in microbial growth?

Answer 4

Length depends on history of the inoculum, time is required to get bio synthetic reactions running

Question 5

What is the log/exponential phase in microbial growth?

Answer 5

Cells are actively dividing and nothing is limiting for growth
Population is doubling in a constant time interval (when under ideal conditions)

Question 6

What is the stationary phase in microbial growth?

Answer 6

Cells stop growing and cryptic growth is observed
Cryptic growth is when organisms survive by consuming lysed cell constituents of other dead cells within the culture
Dynamic population: equilibrium between growing and dying cells

Question 7

What is the death phase in microbial growth?

Answer 7

Cell death
Equilibrium between growing cells and dying cells is skewed towards death

Question 8

Are all cells created equally?

Answer 8

No, growth actually means death rate and growth rate in balance

Question 9

What do prokaryotes need to multiply?

Answer 9

Carbon source : building blocks for macro molecular synthesis
Energy source : energy to drive anabolic and catabolic reactions
Reducing power : carriers of energy/electrons

Question 10

How do prokaryotic cells harvest energy?

Answer 10

Chemical energy is stored in bonds
Broken chemical bonds release energy that can be captured in new bonds
ATP bonds can be broken again later to release that energy

Question 11

What is breakdown and buildup in prokaryotic cells?

Answer 11

Breakdown : catabolism (energy generation), energy/building block harvesting - substrates -> products
Buildup : anabolism (energy consumption), energy/building block use - monomers -> macromolecules

Question 12

What are limitations to pure cultures when studying communities?

Answer 12

Auxotrophs cannot be cultured unless we provide limiting facts
98% of all the microorganisms sequenced so far lack essential pathways or key genes for the synthesis of amino acids

Question 13

What are auxotrophs?

Answer 13

Lacks or is defective in one or more essential genes hence cannot grow unless missing factor is supplied

Question 14

What is a wild type strain?

Answer 14

Has all essential genes, can grow by itself, can be isolated into pure culture

Question 15

What is cross feeding?

Answer 15

One species gains metabolic products of another species
Allows for survival of auxotrophs by harvesting resources generated by other organisms
Interactions can benefit, one or both of the partners

Question 16

What is a microbiome?

Answer 16

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

Question 17

What is a microbiota?

Answer 17

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

Question 18

What are culture dependent methods?

Answer 18

Relies on culturing microbes in the lab
Uses pure cultures or simple enrichments
Pros: allows access to phenotype, can study one organism at a time, can manipulate conditions to see response of organism
Cons: not all organisms can be cultured, too many species to grow them all, requires precise conditions that don’t match real world

Question 19

What are culture independent methods?

Answer 19

Rely predominantly on nucleic acid based methods, no culturing required, uses sequencing or metabolic profiling to study microbes
Pros: Allows access to genotype, study many organisms at a time, show communities as they are in nature
Cons: no pure culture, no ability to manipulate, expensive and complex