Microbial growth Flashcards
What are growth factors?
Organic molecules that the microorganisms need for growth but cannot synthesize by itself. Some growth factors are the by-product or waste of another microorganism.
Exemple of growth factors?
Vitamins, a.a. , purines, pyrimidines or other…
What are siderophores?
Shuttles to get iron. Molecule that will bidn to iron
What form or Iron can be taken up by cells? In what condition?
Ferrous ( 2+) or soluble form , in anoxic condition
What form of Iron cannot be taken up by cells? In what condition?
Ferric (3+) or insoluble. In oxic conditions.
What particular nutrient is limiting nutrient in nature and really important for many enzymes in resp. and photosynth?
IRON
What is growth of a population?
Increase in number of cells or in biomass
Most prokaryotes multiply by…
Binary fission
Steps of binary fission?
- CEll elongation
- Spetum formation
- Completion of septum, formation of walls, cell separation
What enzyme is involved in division of bacteria with peptidoglycan?
Autolysin and Bactoprenol
What is the role of Autolysin?
Destruction of peptidoglycan
What is the role of Bactoprenol?
Allows peptidoglycan subunits to be exported across the cytoplasmic membrane
What will decide where there has to be a fission/ making new peptidoglycan in division of bacteria?
FtsZ ring, or division ring
What is a wall band?
Scar between old and new peptidoglycan
Why is macconkey plate selective?
Because bile salts inhibits growth of Gram +
Why is MacConkey differential?
Because it contains lactose, and a pH indicator: only bacteria fermenting lactose will produce acid–> indicator = pink color on the plate
What does E.Coli form on a macconkey plate?
Dark pink colonies with bile precipitate: “ I don’t care about bile, I will destroy it”
Why is Manitol-salt selective?
Hight in NaCl concentration–> inhibits growth of most Gram -, and many Gram +
Why is mannitol-salt plates differential?
Mannitol fermenters will turn yellow
Exemple of a mannitol fermenter?
Straphylococcus aureus
Name all methods to measure microbial growth/presence.
- Viable Count
- Serial dilution
- Microscopic counts
- Flow cytometry
- Turbidimetric method
Describe viable count method
- Spread-plate method
- Pour plate method
- Need a permissive growth medium
- Results are reliable when there are between 30-300 colonies
How can you get a viable count with serial dilution?
CFU calculation: number of colonies/ dilution plated x volume plated