1. Key Area 6 : Growth in Micro-organisms
Unit 2: Metabolism and Survival

2. Micro-organism Metabolism
Micro-organisms use a wide range of substances for metabolism and can produce a wide range of products.
They are adaptable and found in a wide range of ecological niches.
They are widely used for research and industrial processes.
They produce many products and their metabolism can be controlled and manipulated easily.
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3. Environmental Conditions
What does micro-organism mean: Very small, normally unicellular, micro-scopic. Examples in the 3 domains of life Bacteria Archae Eukarya
Staphylococcus aureus, Escherichia coli, Clostridium botulinum, Diplococcus pneumonia
Methanogens, Thermophiles, Halophiles
Slime moulds, algae, yeast, fungi, plants
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4. Requirements for Growth
Micro-organisms are influenced by the composition of their growth culture or the nutrients that they have access to. The environmental conditions in which they are cultured or exist in are also important.
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5. Requirements for growth
Energy Source
Chemical or Light
Simple chemical compounds
Complex chemical compounds
Sterile culture
Temperature
Oxygen pH
Basic nutrients are required for growth e.g. salts.
Some require things like fatty acids or vitamins that they cannot produce themselves.
Cuts down competition and so allows a much faster growth.
There will be an optimum temperature range for the particular micro-organisms enzymes.
Some will require aeration(bubbling air through) of the culture. Others will only survive in low or no oxygen.
The correct pH needs to be maintained.
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6. Requirements for Growth
Micro-organisms are grown in a laboratory under controlled conditions. A liquid medium called broth or a solid medium called agar is used. Both of these contain essential nutrients that the micro-organisms require.
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7. Requirements for Growth
Bottles, flasks and petri dishes are used to contain the growth medium and control micro-organism growth in a laboratory environment.
For large industrial processes huge, stainless steel fermenters are required.
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8. Requirements for Growth
To ensure the optimum yield of useful product, the environmental conditions during the culture process must be controlled.
What conditions do you think would need to be controlled in a fermenter?
Temperature, oxygen concentration, pH, glucose concentration, aseptic techniques
What are aseptic techniques? Write a sentence describing/explaining these.
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9. Aseptic Techniques
Aseptic techniques are used in the preparation and transfer of growth medium. It is also used in the inoculation of this media with the required micro-organism.
Aseptic techniques will help to ensure that all the conditions involved are STERILE.
This means that contaminants that would affect the growth of the micro-organism are avoided.
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10. Metabolism and
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11. Computer Controlled Fermenters
These fermenters are used to produce huge quantities of products e.g. enzymes, vaccines. If any factors required for the best growth varies outwith the set optimum levels, sensors will pick this deviation up. These sensors will then send this information to the computer running the fermenter. The computer responds to this information and adjusts the supply of the altered condition accordingly until the required level is restored.
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12. Patterns of Growth
Growth can be defined as the point where the rate of synthesis of new organism material exceeds the rate of breakdown of material.
Growth involves an irreversible increase in dry biomass.
Why is dry biomass used?
Dry biomass is used as more reliable indicator of growth compared to fresh biomass as fresh biomass will vary depending on water availability.
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13. Patterns of Growth
For bacteria and yeast cells growth is usually measured by an increase in cell number over a period of time.
The time taken for a cell to divide is called the generation or doubling time.
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14. Growth phases of micro-organisms
Number of micro-organisms
time
Phase name
Lag
Log /exponential
Stationery
Death
What is happening
Slow increase in numbers as cells adjust to conditions. Induce required enzymes for substrates present.
Cells are growing at fastest possible rate. Nothing limits their growth
No increase in numbers. Reproduction = death
Less available resources, metabolites accumulate, secondary metabolites produced
Culture is depleted, lack of substrate and build up of toxic metabolites kills cells.

15. Graphing bacterial growth
Growth curve on graph paper Growth curve on semi-logarithmic paper
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16. Graphing bacterial growth
Growth curve using calculated log values.
Using log values and semi logarithmic graph paper allows the large numbers of microorganisms to be plotted on one piece of paper.
It would also allow a growth rate to be calculated.
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17. Products from micro-organisms
Name some examples of products that are made from micro-organisms.
Large scale
e.g. cheese, wine, beer, sewage treatment ..
More specific
antibiotics / penicillin, insulin, ethanol, methane, human growth hormones, erythropoietin
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18. Control of Metabolism
Micro-organisms control their metabolic pathways naturally.
By inducing or inhibiting enzymes or end –product inhibition.
Some processes require addition of substances to control metabolism and ensure that the required substance is produced.
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19. Control of Metabolism
Adding metabolic precursors: a precursor is a substance that is acted upon by an enzyme to ensure that a desired metabolite is produced later on in the same pathway. They have a positive effect on enzymes
Inducers: an inducer is a substance that triggers the production of a specific enzyme, which then produces a desired metabolite. They start enzyme production for a pathway.
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20. Control of Metabolism
Inhibitors: can be used to avoid the breakdown of a required product. They can affect an enzyme by acting competitively or non-competitively. They control the pathway used by inhibiting certain enzymes
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21. Types of metabolism Micro-organisms can show two types of metabolism.
Primary and Secondary Metabolism.
Where do you think these might occur in the growth cycle of a micro-organism?
Primary metabolism occurs during active growth of the micro-organism – in the lag and exponential phases
Secondary metabolism occurs at the end of the exponential phase and during the stationary phase.
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22. Primary metabolism
Occurs when the micro-organism breaks down a substrate in order to obtain energy and primary metabolites are produced which are essential for growth. This leads to an increase in biomass.
What metabolites are essential for growth?
eg. Amino acids
Humans find some of these primary metabolites useful and have developed industrial processes to collect them.
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23. Secondary metabolism
Secondary metabolism describes metabolic pathways that are not absolutely necessary for survival.
It produces secondary metabolites which are not used for growth or cell division. These metabolites may even be toxic but may also give the micro-organism an ecological advantage.
e.g. antibiotics are secondary metabolites produced by fungi and fall in to this category. Explain why this is.
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24. Secondary metabolism
The fungi is not affected by the antibiotic and does not need it to be present to survive. But it can cut down competition from bacteria present in the fungi ecosystem, which is usually soil.
These secondary metabolites are therefore extremely useful to humans and are cultivated on enormous scales.
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25. Manipulation of Metabolism
An industrial process may rely on a micro-organism that follows a particular metabolic pathway. However, the desired product may not be the natural final product (metabolite D)
The desired product may be C instead.
Metabolite A
Enzyme 1
Metabolite B
Enzyme 2
Metabolite C
Enzyme 3
Metabolite D
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26. How to ensure that metabolite C is mass produced.
Metabolite A would be continuously supplied to be changed into metabolite B by enzyme 1. It would be supplied as a precursor. (phenylacetic acid is added as a precursor to make penicillin)
Metabolite B is provided to act as an inducer and be converted into metabolite C by enzyme 2.
Once metabolite C is produced an inhibitor can be supplied that inhibits enzyme 3 converting metabolite C into D.
Metabolite A
Enzyme 1
Metabolite B
Enzyme 2
Metabolite C
Enzyme 3
Metabolite D
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27. Industrial Processes
Using your text book, the internet and library sources, carry out research into at least 2 industrial processes that use micro-organisms and produce a useful product.
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