Environmental Control of Metabolism Flashcards
define ‘micro-organisms’?
Micro-organisms use a wide variety of substrates for metabolism and produce a range of products from their metabolic pathways.
Give of some examples micro-organisms.
Micro-organisms are archaea , bacteria and some species of eukaryotes.
Why are micro-organisms used?
Micro-organisms are used because of their adaptability, ease of cultivation and speed of growth.
Explain the complex molecules micro-organisms produce and what they are required for?
Many micro-organisms produce all the complex molecules required for biosynthesis, for example amino acids, vitamins and fatty acids. Other micro-organisms require these to be supplied in the growth media.
Describe culturing micro-organisms?
When culturing micro-organisms, their growth media require raw materials for biosynthesis as well as an energy source.
An energy source is derived from either chemical substances or from light in photosynthetic micro-organisms.
State the culture conditions?
Sterility, control of temperature, oxygen levels and pH.
Explain sterile conditions?
Sterile conditions in fermenters reduce competition with desired micro-organisms for nutrients and reduce the risk of spoilage of the product.
Phases of growth and changes in culture conditions
The lag phase- where enzymes are induced to metabolise substrates.
Log/exponential phase- contains the most rapid growth of micro-organisms due to plentiful nutrients.
Stationary phase- occurs to due to the nutrients in the culture media becoming depleted and the production of toxic metabolites. Secondary metabolites are also produced, such as antibiotics. In the wild these metabolites confer an ecological advantage by allowing the micro-organisms which produce them to outcompete other micro-organisms.
Death phase - occurs due to the toxic accumulation of metabolites or the lack of nutrients in the culture.
Explain the difference between ‘viable cell count’ and ‘total cell count’?
‘Viable cell count’ involves counting only the living micro-organisms whereas ‘total cell count’ involves counting viable and dead cells. Only viable cell counts show a death phase where cell numbers are decreasing.
