First day
Making media: Depending on cost, time and availability.
-Buy it already made
-Make it from a mix
-Make it from scratch
Types of Media
There are two main groups of media. Within these groups
are a very large number of different kinds of media.
-Defined media: Know the exact kind and amounts of all
the ingredients.
-Complex media: Generally know the ingredients. The basic
growth requirements of a wide variety of bacteria will be met. Like chicken
soup.
NA: stands for nutrient agar. NB: nutrient broth. TSA: stands for Tryptic soy agar. TSB: Tryptic soy broth. Both are often used in complex growth media. They are similar but different, some bacteria grow differently in one compared to the other.
Physical form of the media
-Liquid (broth): Good for growing bulk amounts of bacteria.
Cannot tell kind or types of bacteria growing as the media simply becomes
cloudy with bacterial growth.
-Solid : Placed in tubes. Has two areas. The surface
has access to air. The rest is the butt area and has little access to air.
Deeps: small surface area. Slants: large surface area.
Typical format is in Petri plates.
- Comes in various sizes.
- Referred to as a Pour plate or Agar plate.
- Wide surface area
-Good for viewing bacteria, separating bacteria
Key ingredient for solid media is Agar
- Agar is a sugar derived from a red seaweed
- Acts as a solidifier. Has very useful properties.
--Inert: it is not broken down by most bacteria.
--Liquid/solid at usable temperatures. Know the temperatures.
Procedure:
-Aseptically transfer the liquid from the tube to the
plate. If necessary, swirl to cover entire plate.
-Labeling: Label on the bottom. Put whatever information
is sufficient so that anyone could use that plate. Typically: Name, date,
type of media, incubation temperature, etc.
-Incubation: The plates are placed upside down to minimize
contaminants and condensation from falling onto the media.
Tips:
- If you wait to long to pour it then it may have totally
or partially (lumpy) solidified.
- If it is not cool enough, i.e. too hot, then it may
melt the plate, and or produce a large amount of condensation.
- Do not flame the lip of the tube. This will be dealt
with later.