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Microbiology - Lecture Twenty Eight : Microbial Population Growth

Q: 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

Q: What microbes need to grow and how they harvest and store energy ?

3 Requirements of Microbial Growth : 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

5 important questions on Microbiology - Lecture Twenty Eight : Microbial Population Growth

What is the process of Binary Fissure ?

Binary fissure results in the formation of two cells that are genetically identical
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

What is the importance of different growth stages and the role of persisters ?

Persisters are insensitive to penicillin because they are in a dormant, non-dividing phase, similar to that of bacteria in the lag phase of the growth curve and because penicillin kills bacteria only when they are dividing or about to divide.

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 ?

3 Requirements of Microbial Growth :

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