Unit 2 KA6 Flashcards
Prokaryote
Organism lacking a true nucleus, eg. bacteria, archaea
Eukaryote
Cells containing a true nucleus, eg. plant, animal and fungal cells
Properties of micro-organisms
Highly adaptable and can grow on a variety of substrates, including waste materials.
Make a wide range of metabolic products which are useful to humans. eg. alcohol, antibiotics.
Easy to cultivate - they grow and reproduce rapidly.
Growth medium
A substance used for culturing micro-organisms.
Can be solid agar or liquid broth.
Various substances can be added to control the metabolism of the micro-organisms being grown.
Composition of growth media
Carbohydrates (eg. starch) - energy source and to build all organic molecules.
Water - (hydrogen/oxygen) for building molecules. Oxygen is required for respiration. (Final H acceptor)
Nitrates and phosphates - for building amino acids, DNA and ATP.
Sulfates - for building some amino acids
Beef extract - contains vitamins and fatty acids which cannot be synthesised by some micro-organisms.
Enzyme inhibitors and inducers to divert metabolic pathways.
Biosynthesis
The production of complex molecules within cells.
Aseptic technique
Sterile conditions used when preparing and inoculating growth media with micro-organisms.
Includes using disinfectant, heating equipment in a flame and protective clothing.
Prevents contamination with rival microbes which may compete with the desired microbe and cause spoilage of the product.
Fermenter
Used to grow microbes in optimum conditions on a large scale to produce antibiotics, enzymes etc.
Sensors/probes
Used to monitor conditions inside a fermenter, so that optimum conditions can be maintained.
Information is fed back to a computer which can alter factors such as the flow rate of cooling water, to adjust the temperature inside the fermenter. (Negative feedback control)
Paddle/stirrer
Blades inside a fermenter that are driven by a motor.
Stirs the culture to prevent the cells from sinking or settling.
Growth
The rate of production of new cells is faster than the rate of cell breakdown, resulting in an increase in biomass (living tissue).
Measuring microbial growth
Dry and weigh a sample of culture to measure biomass.
Or count cell numbers in a known volume using a haemocytometer.
Mean generation time (doubling time)
The time taken for a population of micro-organisms to double in number.
Semi-logarithmic graph paper
Has a normal linear scale along the x-axis and a logarithmic scale along the y-axis.
This allows a large range of values to be plotted.
Microbial populations increase rapidly and are difficult to plot on a normal graph.
Phases of growth
The pattern shown by microbial populations in culture, when number of viable cells is plotted on semi-log graph paper against time.
Shows population growth in 4 phases - lag, log, stationary, death
Lag phase
The cells adjust to the growth medium, and their metabolic rate increases.
They induce enzymes to prepare for growth.
Log phase
A period of exponential growth at the maximum rate possible.
The number of cells doubles with each division, so the population increases rapidly and the graph goes steeply upwards.
Nutrients are plentiful and there are no other limiting factors.
Stationary phase
Rate of new cell production = rate of cell death, and the graph levels out.
Nutrients begin to run out, toxic waste products and secondary metabolites start to build up, and the rate of cell division decreases.
Death phase
More cells are dying than are being produced, due to lack of nutrients and accumulation of toxic products.
The number of viable cells drops.
Viable cell count
Only living cells are counted.
Allows a death phase to be seen.
Total cell count
All cells, viable and dead, are counted.
The death phase cannot be seen in a total cell count.
Haemocytometer
A specialised microscope slide used to count the number of cells in a sample of known volume.
Primary metabolism
Occurs during periods of active growth (lag and log phases)
Substrates are broken down to release energy and produce molecules such as amino acids (biosynthesis) which are essential for growth.
Secondary metabolism
Produces substances that are not used for growth, but which may give an ecological advantage. eg. antibiotics
Happens during stationary phase, when the culture is under pressure and nutrients are running out.
Used to kill rival microbes which may compete for limited resources.
Many secondary metabolites are very useful to humans eg. penicillin (antibiotic)
