Topic 6 Microbiology And Pathogens Flashcards
What are microbial techniques?
Aseptic techniques
- Bunsen burner: create updraft, sterilise air around Bunsen burner
- use disinfectant to clean surfaces
- flame the inoculating loop - sterilise and kills all microorganisms
- autoclave (heat and high pressure to sterilise Petri dish)
Where to culture bacteria and how?
Petri dish containing agar (nutrients like glucose, nitrates)
Put Petri dish on heat proof mat next to Bunsen
Flame and cool inoculating loop, and neck of sample bottle
Dip into bacteria
Slightly open lid of Petri and zig-zag streak on agar
Use tape to seal lid (12, 6 o’clock)
Store in incubator
What temperature would the the incubator for bacteria culture be at and why isn’t it higher?
25 C , 3-5 days
Prevent overgrowth and mutation that could become harmful
Why do we want to culture bacteria?
- test antibiotic resistance
- compare growth rate of bacteria
- identify bacteria then try to invent cure
Agar is a type of…
Culture medium that you grow bacteria on
What requirements are needed for microbial growth?
- organic C source
- N source
- mineral salts K, Mg, Fe
- vitamins
- purine and pyrimidines
All are needed
What are forms of culture media?
- liquid culture (stir w magnet to evenly distribute mineral ions, circulation of Oxygen as well) (can batch or continuous culture)
- solid culture (Agar)(no spillage, useful storage)
What are broad and narrow spectrum culture media?
Broad: can grow lots of generic/different bacteria containing general nutrients
Narrow: only specific bacteria can grow in it, designed specifically for particular microorganism. Inhibits growth of other microbes
How to make sure only specific bacteria grow on agar?
Use antibiotics
What makes antibiotics?
Bacteria to kill other species of bacteria to reduce competition
How do you know you’ve grown the specific species of bacteria you want?
Look at
- colour of colony
- shape/structure
- height
- texture
- colour
- form
What is a selective media?
Isolates bacteria
Can only grow gram positive/negative bacteria
What can grow on MacConkey Agar?
Gram -ve bacteria
How to measure population size of bacteria?
- serial dilution (so sample is less saturated)
- Then count (4 ways)
What are 4 ways of counting bacteria population size?
- haemocytometer (direct count)
- dilution plating (direct count)
- dry mass
- colorimeter
