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Requirements for Growth
Key terms
Macronutrients- required in relatively large amounts, includes carbon, hydrogen, oxygen, nitrogen,
sulphur, magnesium and iron. All nutrients have to be provided in a suitable form in the culture media
in which the microorganisms are grown.

Micronutrients- required in small amounts, may also be known as…

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used as a setting agent in preference to gelatine as it not attacked by the vast majority of
bacteria and it doesn't melt at 37 oc, a temperature often used to incubate bacteria.

Environmental Influences on the Growth of Microorganisms

As temperature increases enzyme activity within the cells also…

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Growth of Cultures

The Important Bits

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Phases of Growth

1. Lag phase- Growth does not happen immediately when the medium is inoculated with a
culture of a microorganism, there is a period where the cells must synthesise the enzymes
required for metabolism of nutrients present in the medium and become adjusted to the
culture conditions.

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Diauxic Growth

This is characterised by two distinct phases
of exponential growth separated by a brief lag phase. It occurs when there are two different carbon
sources to grow on and so once one is used up new enzymes must be synthesised for the
metabolism of the other. For example,…

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Viable cell count- only considers living cells

Cell counts using a Haemocytometer

The number of cells in a suspension can be determined by counting the number of cells present in an
accurately determined, very small volume of culture medium. This is usually carried out using special
microscope slides called Haemocytometers…

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The transfer of the sample should be done as quickly as possible to minimise contamination from
organisms present in the air and surroundings.

Streak Plating

Streak plates are used to isolate pure cultures as individual colonies will have grown from a single
cell. These can then be used to subculture…

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Use of Biotechnology
Food and Drink
Mycoprotein (Quorn)
Single celled Protein (SCP)- made by a microbe rather than an animal
Quorn is a meat substitute for vegetarians designed to provide them with protein.
Fungi used are called Fusarium graminareum.
The whole fungi is harvested and consumed- it is the hyphae…




This a very detailed set of notes that includes growth requirements,fermenters, growth phases, aseptic technique and uses of biotechnology. There are  clear annotated flow diagrams included which help illustrate the key points. Team these up with a set of flashcards that include definitions of the biological terms included in this topic for a complete set of resources.

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