1. Metabolism and Survival
Key Area 6a
Micro-organisms and their growth

2. By the end of this topic you should be able to:
State that microorganisms include bacteria, archaea (thermophiles) which are prokaryotes
State that some species of eukaryotes are also classed as microorganisms e.g. photosynthetic algae
State that microorganisms can use a wide range of substrates for metabolism and produce a wide range of products in their metabolic pathways
State that all microorganisms require an energy source (chemical/light)
Say why simple chemical compounds are necessary in the growth media of microorganisms
Explain why some growth media require more complex compounds
Explain why sterile techniques are important when culturing microorganisms
State that microorganisms require a suitable temperature, suitable oxygen concentration and an optimum pH for growth

3. Microorganisms

4. Microorganisms - introduction
Microbiology is a specialised area of biology that studies organisms that are too small to be seen without magnification. These are known as microorganisms or microbes.
In today's world, microbiology makes up one of the largest and most complex biological sciences because it deals with microbe-human and microbe-environmental interactions.
These interactions are relevant to disease (in both plants and animals), drug therapy, immunology, genetic engineering, industry, agriculture and ecology.

5. Microorganisms
Microorganisms include archaea, bacteria and some species of eukaryote.
They include species that use a wide variety of substrates for metabolism and produce a range of products from their metabolic pathways.
Microorganisms are used because of their adaptability, ease of cultivation and speed of growth.

6. Micro-organism means ..
very small, normally unicellular, micro-scopic
Examples in the 3 domains of life:
Bacteria
e.g….
E.coli, Staphlococcus Aureus,..
Archae
e.g. …
methanogens, thermophiles…
Eukarya
slime molds, algae, yeast

7. Growth of microorganisms (cell culture)
Microorganisms can be cultured relatively easily in a laboratory. They must be given an appropriate growth medium* and the environmental conditions must be carefully controlled to ensure successful growth.
* Growth media – a solid (agar jelly) or liquid (broth) substance used to grow, transport or store microrganisms. The agar is usually found in petri dishes whilst the broth can be in flasks or bottles

8. Growth of microorganisms - media
When culturing micro-organisms their growth media must contain raw materials for biosynthesis as well as an energy source.
Growth media can be composed of specific substances or can contain complex ingredients such as beef extract.
Many micro-organisms produce all the complex molecules required for biosynthesis (amino acids, vitamins, fatty acids). Other micro-organisms require these to be supplied in the growth media

9. Growth of microorganisms - media
Two types of media are commonly used:
complex media contains one or more crude sources of nutrients and their exact chemical composition and components are unknown
- defined media (or synthetic media) is media in which the components of the medium are chemically known and are present in relatively pure form.

10. Growth of microorganisms
Microorganisms require an energy source (which may be chemical or light)
Energy from chemical substrates can be provided in the growth media.
Photosynthetic micro-organisms derive their energy from light

11. Growth of microorganisms – environmental conditions
In industrial processes, microorganisms are grown in large fermenters (or bioreactors) which are constantly monitored and controlled by sensors and computers.
Any necessary change to the environment to maintain optimum conditions is brought about by the computer

12. Growth of microorganisms – environmental conditions
In order to grow cells in culture they must be supplied with a growth media and the correct environmental conditions, including:
Sterility: sterile conditions in fermenters reduce competition with desired micro-organisms for nutrients and reduce the risk of spoilage of the product

13. Growth of microorganisms – environmental conditions
temperature (controlled using an incubator) – essential for maintaining optimum condition for enzymes
pH (controlled by the use of buffers or addition of acid/alkali)
Oxygen levels (controlled using oxygen sensor and sterile air supply) - some microorganisms are anaerobic and will not grow in the presence of oxygen, others will require a good oxygen supply for aerobic respiration

15. Production of the product can also be monitored and the whole process brought to a halt when the required concentration is reached
The advantage of using fermenters is that:
it can be done efficiently on a large scale
it saves energy
no raw materials are wasted

16. Energy source
Chemical or light
Simple chemical compounds
Basic nutrients are required for growth e.g. salts
Complex chemical compounds
Some require things like fatty acids or vitamins that they cannot produce themselves
Sterile culture
Cuts down competition and so allows a much faster growth
Temperature
There will be an optimum temperature range for the particular micro-organisms enzymes
Oxygen
Some will require aeration (bubbling air through) of the culture. Others will only survive in low or no oxygen (again tolerance curve) pH
The correct pH needs to be maintained – tolerance curve