Please enable JavaScript.
Coggle requires JavaScript to display documents.
Growth of Cell populations (All growth media and growth conditions are…
Growth of Cell populations
Nutrients for Cells
Defined media: All the components of the medium are known, together with the amounts of them. These are used in physiological studies to investigate what carbon source a bacterium can use.
Undefined media: The components of the medium are not known. There might be a rich mixture of nutrients present. Used for example in hospital labs to see quickly if organisms are present.
What are nutrients used for?
Carbon - Forms the back bone of all organic molecules
Oxygen: used as an electron acceptor by the electron transport chain. Some can be incorporated into molecular structures
Nitrogen: Proteins and Nucleic acids
Hydrogen: In all molecules e.g water, hydrogcarbon
Phosphorus: Inorganic phosphate, ATP, phospholipids
Sulfur- Coenzyme A, side chains of the aa cysteine, methionine
Metals eg iron and copper used to transfer electrons. Others eg Mg are enzyme cofactors
All growth media and growth conditions are selective
pH for Lactobacillus
Temperature
Amount of Oxygen
Amount of nutrients available
Can be grown in either solid or liquid media
Advantages of liquid is that they can be grown on a variety of scales from a few ml to thousands of litres
Pressure
Radiation
Availability of water
Requirements for air
Obligate anaerobes: Killed by oxygen
Facultative anaerobes: Grow with or without oxygen, might grow better in its presence
Microaerophilic: Some prefer low levels of oxygen
Strict aerobes: have to have oxygen
Lab techniques
Pour plate
spread plate
Streak plate
Doubling time = the time for the number of cell in the population to double in the period of exponential growth
4 main phases when microbial cells are inoculated into broth
Lag phase
adaptation of the cells to their new environment
Log phase
Multiply at a uniform maxium rate. Growth is said to be balanced
Stationary phase
Gradual exhaustion of nutrients. growth rate decreases from the maximum
Death phase
Rate of cell death exceeds the rate of growth
Why grow animal cells?
Bacterial cells are cheaper and easier to grow nut they carry out the wrong post translational modifications
Animal cells produce much more expensive proteins but they carry out the correct processing of the proteins