-
Define cell growth
Steady increase in chemical components resulting in increase in cell size(s) and/or numbers
-
Prokaryotic replication
Binary fission
-
Stages of binary fission
- Cellular elongation
- Replication of DNA
- Division of the cytoplasm
-
Divisisome
Formed by Fts proteins after DNA replication
-
Fts stands for
Filamentous temperature sensitive
-
FtsZ shape and location
Ring formed at centre of cell during binary fission
-
Proteins associated with the divisisome
- ZipA - Anchor
- FtsA - Connector
- FtsI - Peptidoglycan biosynthesis
- FtsZ - The mesh ring itself
-
Septum
Centre of a dividing cell, produced by the divisiome
-
How do MinC, MinD and MinE determine midpoint
- All three inhibit FtsZ ring formation
- MinD spirals along the cell, with greater density at the ends
- MinC is recruited to MinD and inhibits FtsZ
- Mine oscillates from pole to pole, removing MinC and Min D
- As a result, MinC and MinD concentrations are lowest in the middle
-
How is the cell pinched
FtsZ is depolymerized during septum formation
-
MreB
- Shape determining protein in bacteria
- Actin homolog
-
Bactoprenol
- Transports peptidoglycan precursors across the membrane
- Lipid-based
-
Generation time
Time it takes for a cell or population to double in size
-
Equation for number of cells with time (no. of replications)
-
Eqn for generation time
- g = t / n
- (The g is in the top)
-
Batch Culture
Continuous Culture
- Batch: Fixed volume, sealed
- Continuous: Medium is replenished
-
Balanced and unbalanced growth
- Both occur in log phase (batch culture)
- Balanced: All metabolic products produced at constant rates relative to one another
- Unbalanced: Metabolic products vary relative to one another
-
Starvation proteins
- Activated by some cells in low nutrient conditions
- Increases resistance (more peptidoglycan crosslinking etc)
-
The death phase is reversible if conditions are changed? (T/F)
True
-
Chemostat
Incubator-thing used to store and maintain continuous cultures
-
Direct cell counting techniques
- Filtration
- Counter culture
- Flow cytometry
-
Indirect (viable) cell counting techniques
- Viable plate count (CFU/mL)
- Most probable number (MPN)
- Membrane filtration
- Microbial dry weight
- Turbidity
-
Liebig's law
The total biomass of an organism will be determined by the nutrient present in the lowest concentration relative to the organism's requirements
-
Shelford's law
There are limits to environmental factors below and above which a microorganism cannot survive and grow, regardless of the nutrient supply
-
Which part of the cell is most temperature sensitive?
Membrane
-
Psychophile, Mesophile and Thermophile++ temperatures
- Psychro- : 0°C - 15°C (20°C Max)
- Meso- : 15°C - 50°C (25°C - 40°C Optimum)
- Thermo- : 45°C - 85°C
- Extreme thermo- : > 80°C
-
Regular pH range for growth
5.5 - 7.9
|
|
