key area 6 : growth in micro-organisms unit 2: metabolism and survival

Key Area 6 : Growth in Micro-organisms

Unit 2: Metabolism and Survival

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.

CfE Higher BiologyMetabolism

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Environmental ConditionsWhat does micro-organism mean:Very small, normally unicellular, micro-scopic.Examples in the 3 domains of lifeBacteria ArchaeEukarya


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Staphylococcus aureus, Escherichia coli, Clostridium botulinum, Diplococcus pneumonia

Methanogens, Thermophiles, Halophiles

Slime moulds, algae, yeast, fungi, plants

Requirements for GrowthMicro-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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Requirements for growthEnergy Source Chemical or Light

Simple chemical compounds

Complex chemical compounds

Sterile culture

Temperature

Oxygen

pH


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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.

Requirements for GrowthMicro-organisms are grown in a laboratory under controlled conditions.A liquid medium called brothor a solid medium called agaris used. Both of these containessential nutrients that the micro-organisms require.


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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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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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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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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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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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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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Growth phases of micro-organisms

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.

time

Num

ber

of

mic

ro-o

rga

nism

s

Graphing bacterial growth


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Growth curve on graph paper Growth curve on semi-logarithmic paper

Graphing bacterial growth


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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.

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 specificantibiotics / penicillin, insulin, ethanol, methane, human growth hormones, erythropoietin


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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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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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Control of Metabolism


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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

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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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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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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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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Manipulation of Metabolism


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• 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

Metabolite B

Metabolite C

Metabolite D

Enzyme 1

Enzyme 2

Enzyme 3

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.


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Metabolite A

Metabolite B

Metabolite C

Metabolite D

Enzyme 1

Enzyme 2

Enzyme 3

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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key area 6 : growth in micro-organisms unit 2: metabolism and survival

Documents

survival slide

growth microorganisms

growth culture

growth bottles

faster growth

control microorganism

transfer of growth medium

controlled conditions