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  • Created by: Laura
  • Created on: 04-04-14 14:34
Name three shapes of bacterial cell
bacillus (rod) spirillum (spiral) & coccus (spherical)
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What is the cell wall structure of a bacterial cell like?
Singe cell wall - lots of murein & complex layered cell wall
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What is turbidity?
a measurement of light absorption (cloudiness). The more cells, the greater the light absorption. Includes living and dead cells but doesn't give a cell count
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What is haemocymetry?
counting cells under the microscope. the total cell count includes dead cells
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What is dilution plating?
Serial dilution followed by spread plate
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What are bacteria and fungi important for?
decaying dead organisms & releasing/recycling nutrients
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How do bacteria reproduce? (mainly)
Asexually by binary fission
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How are bacteria classified?
shape or gram stain technique (+/-)
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What two types of gram stain can you get?
Positive & negative
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Why do bacteria stain differently?
different chemical compositions in cell walls
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What colour would gram positive bacteria be?
stained violet
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What colour would gram negative bacteria be?
stained red
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Explain the gram stain procedure
1. Basic stain (crystal violet) all bacteria are violet. 2. mordant fixes the stain in place 3. decolouriser makes some bacteria colourless (gram negative) some still violent (gram +) 4. counterstain makes the colourless bacteria appear red (gram -)
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What does bacteria cell walls consist of?
Mixture of polysaccharides & polypeptides = petidoglycan (murein)
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How do cross links aid the cell wall?
strength, shape & protection against swelling & bursting (lysis) due to osmosis
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What is the extra layer gram negative bacteria have?
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What are gram positive bacteria more susceptible to?
penicillin & the enzyme lysozyme. Penicillin interfers with interpeptide linking of peptidoglycan making the cell wall weaker and prone to collapsing and disintegrating when bacteria divides.
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What bacteria require a different class of antibiotics?
Gram negative
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Why do gram negative bacteria require another class of antibiotics?
To interfere with cells ability to make proteins
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How long does it take bacteria to divide?
20 minutes
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Conditions bacteria need for growth
Nutrients, temperature, pH & oxygen
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How are nutrients provided in a lab?
In a nutrient media e.g. agar
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What form does carbon take in a nutrient agar?
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Why is nitrogen in the nutrient agar?
produces amino acids
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Why is temperature important?
growth is regulated by enzymes
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What temperature range is favourable for bacteria?
25-45 degrees
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What temperature is the optimum for most pathogens?
37 degrees
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What pH do bacteria favour?
slightly alkaline
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What pH do fungi favour?
neutral-slightly acidic
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Why is oxygen needed?
For metabolism.
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What is the name given to organisms that require oxygen?
Obligate anaerobes
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What is the name given to organisms that can survive in the absence of oxygen?
Facultative anaerobes
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How would you prevent contamination of pure cultures & apparatus by bacteria in the aseptic technique?
1. sterilise apparatus 2. handle cultures carefully & use equipment such as sterile loops
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How would you prevent contamination to the environment by bacteria?
1. Sterilise work surface before & after 2. use correct handling techniques
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What are endospores resistant to?
Heat, drying, pH change & disinfectant
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What is a fermenter?
industrially cultures micro-organisms
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What is a viable cell count?
counting of living cells
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What is a colony?
A cluster of cells from a single bacterium
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What is a benefit of using a haemocytometer?
more accurate
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What is a negative of using a haemocytometer?
can't distinguish between living and dead cells
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What is turbidimetry?
colorimeter is used to measure cloudiness of the culture
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What is a batch culture fermenter used for?
Culturing bacterial & fungal cells & antibiotics e.g. penicillin
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What are the advantages of a batch culture fermenter?
microbes grow rapidly, enzymes dont have to be supplied, takes place at lower temperatures & production is cheaper
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Why may forced aeration be needed?
For maximum growth of aerobes, which may also mix culture to improve contact with nutrients
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Why is temperature monitored?
maintain constant conditions
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Why are water jackets used in batch fermentation?
remove excess heat
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How long does it take for production of penicillin to begin?
30 hours
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What is penicillin secreted by?
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Why is there a delay in production?
penicillin is a secondary metabolite
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What is a secondary metabolite?
A chemical which isn't necessary for the growth of fungus & is produced after the exponential growth phase, when glucose is depleted e.g. food sources are scarce
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What is a disadvantage of using batch culture?
The fermenter has to be sterilised before being used again
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What is continuous cultivation suitable for?
Primary metabolites
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Why is continuous cultivation good?
allows production to continue for much longer
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Give examples of products produced with continuous cultivation
Alcohol & insulin
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In continuous cultivation what is added throughout the process?
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When are the products removed in continuous cultivation?
All the time
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Other cards in this set

Card 2


What is the cell wall structure of a bacterial cell like?


Singe cell wall - lots of murein & complex layered cell wall

Card 3


What is turbidity?


Preview of the front of card 3

Card 4


What is haemocymetry?


Preview of the front of card 4

Card 5


What is dilution plating?


Preview of the front of card 5
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