Term
| What is the kingdom of bacteria? |
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Definition
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Term
| How can bacteria be distinguished? (6- SSSMAG) |
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Definition
-Sie
-Shape
-Staining characteristics
-Metabolic features
-Antigenic features
-Genetic features |
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Term
What are the names of three types of bacteria? (Give examples)
-Spheres
-Rods
-Spirals |
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Definition
-Cocci- Streptococcus
-Bacilli-E.coli
-Spirals-Spirilum |
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Term
| What ribosomes do bacteria have? |
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Definition
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Term
| What causes the difference in shape in bacteria? |
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Definition
The shape of bacteria is due to their rigid cell wall which
has a unique structure: it contains a 3D mesh of
peptidoglycan (murein). |
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Term
| What is the typical length of bacteria? |
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Definition
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Term
| What is meant by autotrophic? |
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Definition
| Synthesise cell constituents using CO2 as the C source |
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Term
| What is meant by phototautotrophic? |
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Definition
| Either photosynthesise with chlorophyll as an e- donor or alternatives using S or H gas as an e- donor |
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Term
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Definition
| A molecules that causes the immune system to produce antibodies against it |
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Term
| Give the sequence of gram staining and colour of the gram -ive bacteria |
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Definition
1.Application of crystal violet
2.Application of I2
3.Alcohol wash (decolourisation) differential stage - Gram -ive turns colourless
4. Application of safranin (a counter-stain) gram -ive turns red/pink |
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Term
| Which bacteria contains the lipopolysaccahride? |
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Definition
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Term
| Which bacteria is not susceptible to penecilin? |
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Definition
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Term
| Give an example of gram + and - |
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Definition
+ = streptococcus
- = salmonella |
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Term
| Describe the gram + cell wall |
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Definition
Thick peptidoglycan layer
No outer liposaccharide |
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Term
| Describe the gram - cell wall |
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Definition
Lipopolysaccharide layer- made from a polysaccharide attached to a lipid
Thin peptidoglycan layer |
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Term
| Explain why gram + and gram - bacteria look different under the microscope |
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Definition
Gram + bacterial cell walls take up & retain the crystal violet dye
Gram - bacterial cell walls are treated with alcohol which removes the outer layer of lipopolysaccharide allowing safranin to stain the thin layer of peptidoglycan red |
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Term
| What is the function of the peptidoglycan layer? |
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Definition
| Support to prevent osmosis pressure causing damage (lysis) to cell |
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Term
| What is the function of the plasma membrane? |
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Definition
| Controls what enters and leaves as it is selectively permeable |
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Term
| How to bacteria reproduce? |
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Definition
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Term
| What temperature facilitates bacterial growth? |
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Definition
| 25-45C mammalian pathogen is at 37C |
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Term
| What nutrients do bacteria require for growth? |
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Definition
| Agar, liquid broth. Glucose for carbon source N for amino acids and nucleic synthesis as NO4- |
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Term
| What pH do bacteria require for growth? |
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Definition
Alkaline conditions
Fungi neutral and slightly acidic |
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Term
| What is an obligate aerobe? |
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Definition
Only survive and metabolise in presence of O2
e.g. clostridium tetani |
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Term
| What is an obligate anaerobe? |
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Definition
| Only survive and metabolise in the absence of O2 e.g. E.Coli |
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Term
| What is a facultative anaerobe? |
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Definition
Metabolise better in O2 but can survive without it
e.g. TB |
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Term
| Name 2 substrates that can be used to release energy in respiration |
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Definition
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Term
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Definition
| No/little cell division. Intense metabolic activity such as enzyme synthesis |
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Term
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Definition
| Rapid increase in numbers, no limiting factors to growth. Cell division higher than death rate. Plenty of glucose available |
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Term
| Describe the stationary phase |
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Definition
| Limiting factors prevent further growth of the population. E.g. competition for glucose. Carrying capacity has been reached. |
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Term
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Definition
| Limiting factors cause the population size to decrease. Death rate is higher than cell division. This could be due to build up of toxic waste, or no glucose left in the medium |
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Term
| What are two main purposes of aseptic techniques? |
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Definition
-Preventing contamination of pure cultures by environmental microbes
-Preventing contamination of the environment by cultures being grown |
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Term
| How can contamination be prevented by environmental microbes? |
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Definition
-Sterilise all media and equipment
-Handle carefully flame neck of culture bottles before opening and closing
-Use a Bunsen burner to create convection current
-Disinfect workbenches beforehand |
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Term
| How can contamination of the environment be prevented? |
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Definition
-Sterilise work surfaces before and after experiments using a disinfectant
-Lift agar dish lid to no more than 45 degrees
-Seal agar dishes with adhesive tape, but not all the way around
-Flame the neck of the culture bottle without placing the cap on the work surface |
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Term
| How does sterilisation happen in an autoclave? |
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Definition
-Sealing it in an autoclave bag
-Heating it to 121C in steam (above boiling point)
-Applying high pressure for 15 minutes |
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Term
| How to sterilize with gamma radiation and what it is used for? |
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Definition
-Plastic sterilised with radiation
-After use the plastic equipment can be disposed of in a biohazard waste bin or sterilised in an autoclave |
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Term
| What is total cell count? |
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Definition
| Living and dead cells in a bacterial sample |
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Term
| What is total viable count? |
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Definition
| Living cells in a known volume of liquid medium |
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Term
| What is a haemocytometer and how is it used? |
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Definition
A microscope slide with a grid-engraved rectangular chamber.
The chamber has a known depth, allowing the n of cells in a specific volume to be counted.
A coverslip is placed over the chamber and the slide is observed under a microscope to count the cells |
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Term
| Which lines are not counted in a haemocytometer? |
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Definition
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Term
| What type of count is serial dilution? |
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Definition
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Term
| How do you find number of bacteria in serial dilution? |
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Definition
| Count number of distinct colonies and multiply by the dilution factor |
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Term
| What inaccuracies may occur when carrying out a serial dilution if the original bacterial culture is under diluted? |
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Definition
| Colonies might merge, referred to as 'clumping' and counting may be inaccurate resulting in an under estimate of cell numbers |
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Term
| What inaccuracies may occur when carrying out a serial dilution if the original bacterial culture is over diluted? |
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Definition
| There will be too few colonies on each plate to count to be statistically sound |
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Term
| How are cells indirectly counted? |
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Definition
| By measuring turbidity (cloudiness) of the culture gives an indirect measure of growth |
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Term
| How is turbidity measured? |
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Definition
| Involves using a colorimeter to measure the turbidity (cloudiness) of a culture as cell numbers increase |
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Term
| How are bacterial population measurements obtained? |
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Definition
| By finding the suspension's absorbance value and graph on light absorbance against n of bacterial cells |
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Term
| What type of cell count is turbidity? |
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Definition
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