Lab #2 Flashcards
All culture media must provide what components?
1) Major elemetns (C, H, O, N, P, S)
2) Minor elements (Fe, Ca, K, Mg, etc)
3) Trace needs (e.g., vitamins)
4) An energy source
5) Buffering capacity
6) Special needs (e.g. unique terminal electron acceptors or donors, unique temperatures or other physical parameters)
What are the two types of bacterial media?
Complex or defined
Define broth
A liquid based medium provided in either tube or flask. Broth tubes are filled after thorough mixing. These broth tubes must be sterilized to ensure having sterile media for your cultures
Define agar
An extract of seaweed that can be used to make a solid, gel-like product after heat sterilization. The spaces within the agar matrix will be filled with whatever aqueous phase was mixed with the agar initially. Thus, beef-based, soy-based, and any number of aqueous additions can be made.
Define petri dish
A shallow dish with a loose fitting lid designed to hold a relatively small volume of molten agar, which then solidifies, giving a sold flat surface to grow cultures. They can be made out of glass or plastic; most are plastic and come pre-sterilized
Define agar slant
Agar-based media poured into a test tube prior to heat sterilization; upon removal from the autoclave, these tubes are placed on a slant and allowed to cool where they solidify, leaving a solid slanted surface in the tube. Media produced in slants is much less susceptible to drying than in agar petri dishes.
Define complex medium
The major constituents of this medium are provided by extracting components of plants or animals; the most common being soybean or beef based, because they provide a complex mixture of carbohydrates, proteins, lipids, nucleic acids, and other elements not easily defined. In general complex media are used to grow the largest number of different types of bacteria.
What were the two types of media used in lab 2?
Tryptic soy broth (TSB) and tryptic soy agar (TSA)
Define an autoclave
A device used to sterilize equipment/ supplies by subjecting them to high pressure saturated steam at 121C for 15-20 minutes
What do you use with a magnetic stirrer?
A hot plate
Describe what was done with the TSB media in lab 2
1) Measured out 9 grams of TSB powder and combined with water in a flask to produce 300ml of media
2) Transferred 10ml of the media to each of the 30 tubes
3) Capped the tubes, and removed one tube and labelled it as “nonsterile”
4) Tubes were then put in the autoclave
Describe what was done with the TSA in this lab
1) Measured out 9 grams of TSB powder and mixed with 4.5 grams of agar as well as water to make 300ml of molten agar; a hot plate and magnetic stirrer were used to ensure it was mixed well.
2) Transferred 12ml of the solution into 25 tubes
3) Capped the tubes and labelled them as TSA slants
4) Autoclave
Describe how autoclaves work
They work because moist heat kills due to:
1) Increased motion of molecules
2) Cleavage of H bonds in/between proteins
3) Water molecules in steam become more energized
4) More penetration (into liquids/ surfaces)
Describe what was learned in lab 2 overall
The preparation of bacterial culture-based media
