1What is the circular bacteria called, how is it shaped
Coccus (1), cocci (2+)
Spherical shaped
2What is the long bacteria called, how is it shaped
Bacillus (1), bacilli (2+)
Rod shaped
3What is the sprial bacteria called, how is it shaped
Spirillium
Spiral / corkscrew shaped
4What can bacteria be classified as?
Gram negative (red), gram positive (purple)
5How to test what type bacteria is
• Smear bacteria sample onto glass slide
• Heat to fix sample
• Stain with crystal violet
• Put iodine on to fix stain
• Decolourise with alcohol to remove unbound stain
• Use counter stain Safranin
6How can you tell what gram positive bacteria is after staining
Only has thick pepticoglycan cell wall so retains crystal violet stain
7How can you tell what gram negative bacteria is after staining
Has lipopolysaccharide layer to protect thin pepticoglycan wall
Lipopolysaccharide layer doesnt retain crystal violet so washed away by alcohol
Stains red bc of Safranin
8What does the lipopolysaccharide wall do?
Protect thin pepticoglycan gram negative wall
Protects against lysozymes and penicillin
So more difficult to control
9What does total count mean
Number of alive and dead cells in sample
10What does viable count mean
Number of alive cells only in sample
11What type of count is used in serial dilution
Viable count, only the living cells can divide to form a colony
12between how many colonies should you use to count
inbetween 10-100 colonies
13How do you serial dilute
•1cm3 of water in tube
•0.1cm3 of sample
• Put in first tube and mix
• Take 0.1cm3 of first tube sample and repeat
• Repeat until you get to 10,000 dilution factor
• Count no. of colonies seen
14Why should you use between 10-100 colonies to count
Over 100- too many to count, colonies may merge together
Under 10- not enough to reliably estimate
15What do microbes need to grow
Nutrients- Needs carbon source to grow (eg, glucose)
Optimum pH (7.4)
Optimum Temperature (25°-45°)
Oxygen for metabolism
16What are the 3 different types of microbes in terms of needing oxygen
Obligate anaerobe- needs no oxygen
Obligate aerobe- needs oxygen
Facultative anaerobe- can thrive in both, rathers oxygen
17What is aseptic technique used for?
Prevent contamination of environment by sample
Prevent contamination of culture by microbes from environment
18How do you practice the aseptic technique?
• Sterilise equipment b4 and after by heating it on bunsen burner on red flame
• Use inoculation loop to transfer bacteria
• Lift petri dish lid slightly when transfer prevent environment microorganisms contaminating
• Secure lid with tape
• Sterilise
19What are the four types of culture
Defined medium
Undefined medium
Selective
Complete
20What is a defined medium culture
Only known ingredients in the culture
21What is a undefined medium culture
Not all of the ingredients are known
22What is a selective medium culture
Only allows certain bacteria to grow
23What is a complete medium culture
Contains all chemicals needed to grow