Microbial Population Growth

Question 1

Why are prokaryotes so dominant

Answer 1

Fast growth rate (as low as 13 minute doubling time)
Fast growth allows for fast evolution

Question 2

What is binary fission

Answer 2

Chromosomes replication begins
One copy of the origin is now at each end of cell
Replication finishes
Cell devices into two (cytokinesis)
Two clone daughter cells

Question 3

What is the genetic makeup of daughter cells of binary fission

Answer 3

Genetically identical

Question 4

Why are prokaryotes so diverse

Answer 4

Fast growth + 3.5 billion years allowed colonisation of all ecosystems
Prokaryotes were sole inhabitants for 1.7 billion years
Most habitats were colonised
Extreme ecological and metabolic diversity

Question 5

Outline the cellular requirements of microbial cells and eukaryotes

Answer 5

Microbes need same building blocks, just in different amounts
If we supply them with all required materials the can reproduce

Question 6

What is a closed batch culture

Answer 6

A form of cell culturing
Defined amount/supply of nutrients is provided
Once used, cells cannot proliferate
Standard method of studying microorganisms in culture
Dictated by method, not shape of flask

Question 7

What are the feast and famine phases of microbial growth

Answer 7

Feast: Lots of nutrients to grow on
Famine: nutrients devoid environment

Question 8

What is the lag phase of cellular growth

Answer 8

Length depends on history of the inoculum, time is required to get bio synthetic reactions running. Generally characterised by metabolic activity but not growth

Question 9

What is the exponential phase (log growth) of cellular growth

Answer 9

Cells are actively dividing and nothing is limiting growth. Population is doubling at constant time interval

Question 10

What is stationary phase of cellular growth

Answer 10

Cells stop growing and cryptic growth is observed

Question 11

What is cryptic growth

Answer 11

Organisms survive by consuming lyses cell constituents of other dead dells within population
Population is not static, but is dynamic. Equilibrium between growing and dying cells

Question 12

What causes stationary phase of bacteria growth

Answer 12

Run out of nutrients to sustain expanding population
Competition for resources
Produce toxic end products (closed system, are not removed)

Question 13

What is cell death phase

Answer 13

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

Question 14

What 3 things do microorganisms need to grow

Answer 14

A carbon source = building blocks for macro molecular synthesis
An energy source = energy (electrons) to drive anabolic (making) and catabolic (breaking) reactions in cell
Reducing power = carriers of energy/electrons (NAD+/NADP+)

Question 15

What does the photosynthetic electron transport chain produce for the cell

Answer 15

Transforms light energy into carbs, NADPH, and APT

Question 16

Where do microbes harvest carbs from

Answer 16

Microbes harvest carbs from autotrophs as sources of carbon/energy

Question 17

How do microorganisms harvest energy

Answer 17

Molecules = natures batteries (glycolysis)
Chemical energy stored in bonds
Breaking of bonds releases energy that can be captured in new bonds (ATP)
ATP bonds can later be token to release energy

Question 18

What is a photoautotroph

Answer 18

Organisms that use light energy and inorganic carbon to produce organic materials

Question 19

What is a photoheterotroph

Answer 19

organisms that use light for energy, use organic compounds as their sole carbon source

Question 20

What is a chemoautotroph

Answer 20

Organism that used chemical energy, and fixation of inorganic substances for carbon

Question 21

What is a chemoheterotroph

Answer 21

Organisms that use chemical energy, carbon from organic compounds

Question 22

What is a genomic strain when studding communities

Answer 22

Wild type strain might have all genes necessary, can be grown in isolated pure culture
Auxotroph got be lacking/defective in one or more essential genes
Cannot grow unless missing factor is supplied (might be supplied by other organism in wild)

Question 23

What % of microorganism are auxotrophs, and how do the survive in the wild

Answer 23

98% of all microorganism sequenced so far lack essential pathways or key genes for synthesis of Amin acids
Something else provides missing substance in wild

Question 24

What is an auxotroph

Answer 24

An organism that is unable to synthesise one or more essential growth factors, and cannot grow unless this is provided

Question 25

What is cross feeding

Answer 25

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

Question 26

What is a microbiome

Answer 26

Complete collection of mircoorganisms and there genes within a particular environment

Question 27

What is a microbiota

Answer 27

Individual microbial species in a biome

Question 28

What are the 3 ways of studying the microbiome

Answer 28

Metagenomics
Metatranscriptonics
Metabiomics

Question 29

What are the pros and cons of studying the microbiome using culture dependant methods

Answer 29

Pros: Allows access to phenotype, can study one organism at a time, can manipulate conditions to see response of organism
Cons: Not all organism can be cultured, Too many species to grow them all, culturing requires precise conditions to match microbes needs, does not match real world conditions

Question 30

What are the pros and cons of studying microbiome using culture independent methods

Answer 30

Pros: Allows access to all genotypes, 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
Cons: No pure culture so no ability to manipulate, expensive and complex methods