Lecture 2 - Jennifer Culturing Microbes Flashcards
function of aseptic technique
To prevent contamination
Before handling and growing microbes what is required
A sterile growth media
What is the Latin meaning for “medium”
Middle
Name the types of medium
•liquid
•water based (broth)
•solid (agar petri plates)
Name the common methods of sterilising bacterial growth media
•boiling
•autoclave
•dry heat
Write a short note on boiling
100 degrees celcius
For 30 minutes
Kills cells
Write a short note on autoclave
121 degrees celcius
For 30 minutes
Kills all cells and spores
Write a short note on dry heat
150 degrees celcius
For 120 minutes
Kills all cells and spores
Name the five l’s for handling microorganisms
1.Innoculation
2.Incubation
3.Isolation
4.Inspection
5.Identification
Growth in a nutrient broth can be observed as what kind of suspension
A cloudy suspension
What is a cloudy suspension in a nutrient broth termed as
A culture
What temperature does agar melt at
100 degrees Celsius
What temperature does agar solidify at
40 degrees Celsius
Name the method used to sterilise agar
Autoclaving
What do bacteria grow as on agar
Colonies
Each bacterial colony is derived from what
A single cell
Single colony purification =
Single bacterial cell purification
Where are microorganisms grown
In an incubator
What makes an incubator suitable for growing microorganisms
It provides optimal temperature and gas content
What does an incubator speed up
The process of multiplication and production of a culture
How many different media for growing bacteria
> 500
What do different colony types mean
The culture is not pure
Disadvantage of broth culture
Not possible to determine if growth of more than one bacterial species has occurred
Name identification methods for microorganisms
•Macroscopic or colony morphology
•Microscopic morphology
•biochemical characteristics
•genetic characteristics
Define sterilisation
Removal and destruction of all microbes in or on an object
Describe physical heat method for the disposal of cultures
•moist heat,boiling, flowing steam
Cells and most viruses - not spores
•Tyndallization - intermittent boiling
•steam (autoclaving) 121 degrees celcius for 15-30 minutes
All spores , viruses , cells , media and equipment
•dry heat ( hot air) 1 hour at 171 degrees
•incineration (burning) 1 second or more at 1000 degrees celcius
Describe radiation methods for disposal of cultures
•Ionising eg- x rays , gamma rays , secs-hrs , OH- radicals , damage to DNA
•sterilise pharmaceuticals and medical supplies
•non ionising eg- UV light ,DNA damage , operating theatres , kitchens
Name gaseous avengers used for chemical sterilisation methods
Ethylene oxide
What causes cell death in chemical sterilisation methods
EtO alkylates
Nucleic acids
Proteins
Enzymes
How long are cycles for chemical sterilisation methods
12 - 24 hours
What is ethylene oxide sterilisation commonly used for
Sterilisation of surgical equipment in hospitals
Write a short note on pasteurisation
Use of heat
75 degrees celcius for 15 seconds
Kill pathogens and reduce number of spoilage microorganisms in good and beverages ( milk , fruit juice , wine , beer)
What are antiseptics
Microbicidal agents harmless enough to be applied to skin and mucous membrane
Examples of antiseptics
Mercurials
Silver nitrate
Iodine solution
Alcohols
Detergents
What are disinfectants
Agents that kill microorganisms but not necessarily their spores not safe for application of living tissues they are used on inanimate objects like tables,floors
Example of disinfectants
Chlorine
Hypochlorites
Chlorine compounds
Copper surface
Quaternary ammonium compounds
What are disinfectants and antiseptics distinguished on the basis of
Whether they are safe for application to mucous membranes
Safety often depends on concentration of compound
Eg: sodium hypochlorite (chlorine) as add to water is safe for drinking but chlorox (5% hypochlorite) is an excellent disinfectant not safe to drink
