MMB03 Microbial Growth Flashcards
How do bacteria divide
Binary fission
What are the downsides to using microscopy or viable counts to measure microbial growth
It’s very laboratory intensive
Very time consuming
What is Turbidity
Turbidity is the measure of optical density of a liquid (cloudier liquids are more Turbid)
How can we use turbidity in microbial growth
The increasing turbidity caused by the increase in microorganisms as they multiply can be measured with a spectrometer and used to quickly and easily make growth curve
What are the phases of a bacterial growth curve
Lag phase
Exponential phase
Stationary phase
Death phase
What happens during the lag phase
Microbes are adapting to the new environment. They need time to produce the necessary biochemical components required for growth.
If a culture is transferred to a new medium with the same conditions then there will be no lag phase as the microorganisms are already adapted
What happens during the exponential phase
Bacteria are growing and multiply exponentially through logarithmic growth.
What happens during the stationary phase
The rate of cells multiplying is equal to the rate of cells dying resulting in no net growth.
This occurs when an essential nutrient for cell growth is depleted
Or when a biproduct of growth accumulates and inhibits cell growth
Many other cell functions like energy metabolism and biosynthesis still take place
What happens in the death phase
Cells start dying, in some cases the cells will undergo lysis.
Cell death is also exponential, but at a much slower rate than cell growth
What is a psychrophile
A microorganism that grows most optimally in cold conditions between -5-10 C
What is a mesophile
A microorganism that grows most optimally in warm conditions between 15-45 C
What is a thermophile
A microorganism that grows most optimally in hot conditions between 45-70 C
What is a hyperthermophile
A microorganisms that grows most optimally in very hot conditions over 70 C
Why are thermophiles and hyperthermophiles useful in industry?
There enzymes work at very high temperatures without being denatured. High temperatures allow for many industrial processes to occur more efficiently
What are acidophiles
Microorganisms that grow best below pH 5.5
What are alkaliphiles
Microorganisms that grow best above pH8
What is a nonhalophile
Microorganisms that do not grow very well in salty conditions
What is a halotolerant
Microorganisms that grow best in mildly salty conditions below 10%
What is a halophile
Microoganisms that grow best in salty conditions
What are the different categories of oxygen requirements
Obligate aerobes
Facultative anaerobes
Obligate anaerobes
Aerotolerant anaerobes
Microaerophiles
What is an obligate aerobe
Organisms that can only grow aerobically in the presence of oxygen. Can remove toxic forms of oxygen
What is a facultative anaerobe
Can grow both aerobically and anaerobically, usually prefer aerobic growth. Can remove toxic forms of oxygen
What is an obligate anaerobe
Can only grow anaerobically without the presence of oxygen. Can not remove toxic forms of oxygen so will die in aerobic conditions
What are aetotolerant anaerobes
Can only grow anaerobically. It can however remove toxic forms of oxygen so can survive in aerobic conditions
Microaerophiles
Can only grow aerobically in areas with a low oxygen concentration. Higher levels of oxygen are lethal and it can not grow
Why is oxygen toxic to some microorganisms
All organisms can reduce oxygen, however this produces toxic biproducts like hydrogen peroxide and oxygen radicals.
Aerobic or aerotolerant microorganisms can remove or neutralise these toxic forms of oxygen
However obligate anaerobes can not and will die
What anabolic mean
Processes that build up substances like the biosynthesis of macromolecules
What does catabolic mean
Processes that lead to energy conservation, usually through breaking down bonds in molecules e.g. the breakdown of ATP into ADP
What is a defined culture media
Prepared by adding highly purified chemicals to distilled water
What is a complex culture media
A highly nutritious media where the exact composition is unknown making it easier to prepare than a defined media.
Used when high growth is required but the knowledge of the exact composition is not essential
What is general purpose culture media
A media that can culture a wide range of different bacteria
What is a selective culture media
A media that contains compounds that inhibit the growth of some microorganisms but not others
What is a differential culture medium
A medium where an indicator is added that shows whether a chemical reaction has taken place
