lecture 28 - microbial population growth Flashcards
How do prokaryotes reproduce?
Asexually - via binary vision
What is the closed batch culture system?
A system in which cells can be grown in a closed environment, with limited nutrients only provided initially.
What are the 4 key phases of growth in a closed batch culture system?
Lag, exponential, stationary, death
What is the first growth stage of the closed batch culture system?
Lag
What is the second growth stage of the closed batch culture system?
Exponential
What is the third growth stage of the closed batch culture system?
Stationary
What is the fourth and final growth stage of the closed batch culture system?
Death
What is the lag phase of a closed batch culture system?
When very little growth is observed because time is required to get bio synthetic reactions up and ready and for the organisms to adapt to their new conditions.
What is the exponential phase of a closed batch culture system?
Phase when cells are actively dividing with aid of nutrients, with no factors limiting their growth. Population doubles over a constant time interval, under ideal conditions
What is the stationary phase of a closed batch culture system?
Phase when there is no net cell growth (cryptic growth) All nutrients are used up and organisms are surviving and replicating by consuming dead/lysed cells. The rate of growth and death is constant.
What is cryptic growth?
A phenomenon observed in a closed batch culture system, where there appears to be no bacterial growth, or even a decline, but growth still occurs at a rate equal or less than the rate of death of cells.
What is the death phase of a closed batch culture system?
When the system is no longer viable, so cells begin to die at a rapid rate, and the equilibrium is skewed towards death.
How can the culture at the stationary phase in a closed batch culture system be described?
At a static equilibrium
What are the 3 requirements for microbial population growth?
Carbon source, energy source, reducing power
Why is a carbon source required for microbial population growth?
Carbons provides the building blocks for macro molecular synthesis.
Why is an energy source required for microbial population cell growth?
Energy stored in electrons is used to drive anabolic and catabolic reactions in the cell.
How is reducing power utilised in microbial population growth?
NAD+/NADP+ can be reduced to carry electrons in biological processes
How is energy harvested by microbes for growth and function?
Chemical energy stored in bonds is released and captured by ATP when bonds in fuels, such as glucose, is broken.
What is the overall type of reaction that allows for the transfer of energy in a bacteria?
Redox reactions
What is catabolism, in terms of metabolism?
Generating energy by breaking big molecules down into building blocks and releasing chemical energy.
What is anabolism, in terms of metabolism?
Using energy and building blocks/monomers to build larger molecules and store chemical energy.
What are the 4 types of bacteria, in terms of their energy and carbon source?
Photoautotrophs, chemoautotrophs, photoheterotrophs, chemoheterotrophs
What type of bacteria get their carbon by fixing CO2?
autotrophs
Why type of bacteria rely on extracellular sources of carbon - i.e. cannot fix their own?
heterotrophs
Where do heterotrophs get their carbon from?
Organic compounds
Where do autotrophs get their carbon from?
The fixing of carbon dioxide.
What type of bacteria get energy from light?
Phototrophs
What type of bacteria get their energy from chemical compounds?
Chemotrophs
What is a wild type strain?
A microbe strain that has all the essential genes to be grown by itself in pure culture - is not reliant on outside sources of nutrients.
What is an auxotroph?
A microbe that is defective in one or more essential genes that means it will not grow/cannot be cultured without limiting factors being added.
What is cross feeding, in terms of microbial growth?
When one species gains the metabolic products/byproducts of another species allowing for the coexistence of microbes that cannot metabolise everything they need to survive on their own.
What is a microbiome?
A complete collection of micro-organisms and their gene pool that exist within a specific environment.
What is the name for an individual microbe within a microbiome?
microbiota
What is a culture dependent study?
A method to culture specific microbes so their phenotypes can be easily accessed and their conditions can easily be manipulated.
What are the pros of a culture dependent method of microbe study?
Allows access to phenotype of specific organism. Can see how changing conditions affects a specific organism.
What are the cons of a culture dependent method of microbe study?
Not all organisms can be cultured, too many species to grow them all, precise conditions must be met, doesn’t it match real world conditions
What is a culture independent study?
Study where bacteria are not cultured, but genetic sequencing and metabolic profiling are used to study all of the microbes in a sample.
What are the pros of a culture independent method of microbe study?
Allows access to microbial genotypes, can study many organism ad how they interact, can study non-culturable organisms.
What are the cons of a culture dependent method of microbe study?
No pure culture, so cannot easily manipulate microbes.
