Microbiology - Lecture Twenty Eight : Microbial Population Growth
5 important questions on Microbiology - Lecture Twenty Eight : Microbial Population Growth
What is the process of Binary Fissure ?
PROCESS :
- Chromosome replication begins
- One copy of the origin is now at each end of the cell
- Replication finishes
- Two daughter cells result
What is a "closed Batch Culture System" ?
- Refers to a form of cell culturing
- Defined (limited amount) supply of nutrients is provided
- Once used (become limited) cells cannot proliferate
- Standard method of studying microorganisms in culture
- Dictated by method not shape of flask
What are the 4 microbial growth stages of bacteria in a "Closed Batch Culture System" ?
- Lag Phase : length depends on history of the inoculum, time is required to get biosynthetic reactions running
- Exponential Phase (log phase) : Cells are actively dividing and nothing is limiting for growth. Population is doubling in a constant time interval (under ideal conditions)
- Stationary Phase : 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
- Death Phase : Cell death. Equilibrium between growing cells and dying cells is skewed towards death
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What is the importance of different growth stages and the role of persisters ?
- Penicillin = Antibiotic
- Kills bacteria by blocking cell wall synthesis. Only growing/replicating bacteria affected.
What microbes need to grow and how they harvest and store energy ?
- Carbon Source : Building blocks for macromolecular synthesis
- Energy Source : energy to drive anabolic and catabolic reactions in the cell
- Reducing Power : carriers of energy/electrons (NAD+/NADP+)
Microbial organisms that use light as an energy source are known as photo-trophs; whereas those that utilise chemical energy are known as chemo-trophs. Microbial organisms that use carbon dioxide as a carbon source are known as auto-trophs ; those that use organic compounds as a carbon source are known as hetero-trophs
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