MicroBio Lab Quiz 4

Complex growth media

Complex growth media

Yeast extract:
- Use yeast to make alcohol
- After alcohol is made end up with yeast cells
- Yeast cells are nutritious
- Take yeast from brewery dry it, and mix up into mixture
~don't know the molecular formula for yeast cells

No formula (Peptone)

Defined growth media

Known chemicals in precise amounts
Sodium chloride (NaCl) 2.5g

Chemical formulas

Growth media can be -

Liquid, solid, semi-solid

Agar is?

a polysaccharide that comes from algae

When is Agar solid?

below 42-45 degrees Celsius

If you put agar in liquid and bring it to _________ temp it will dissolve and melt

boiling (100 degrees Celsius)

Is Agar metabolized?

no

Agar

Solid is like agar
- We make solid medium when we take liquid medium and add a solidifying agent which could be agar

- Cool it down to solidify it

- Heat it up to melt it

Many bacteria can metabolize _______________, this is why we don't use it

gelatin

Semi-solid is like -

loose jelly

Sterilization

- Always want the medium to be sterile
- Autoclave used for sterilization
- No degrees of sterilization
- Something is either sterile or not sterile

What type of heat does the autoclave use?

moist

(much better at sterilizing things than dry hot air)

How is 121 degrees Celsius achieved with the autoclave?

the pressure

(just heat will not get anything about 100 degrees)

Why do we need the autoclave temperature at 121 degrees Celsius?

to kill endospores

Alternatives to autoclaves are:

- Chemicals (gasses)
- Radiation (most plastic things are sterilized through radiation)
- Filtration (used with syringes)

Serratia marcescens

rod shaped, gram -, produces pink pigment

Klebsiella pneumonia

rod shaped, gram -, causes pneumonia, known to produce capsules

Agar slant

- Inoculate it in 2 ways
o 1st way - go in slant and draw zig zag using the loop
o 2nd way - insert needle all the way to bottom of test tube
- Use needle to check for growth in anaerobic (anaerobic without air, without oxygen)

Streak plate method

the point of this method is to obtain isolated colonies

what are the most common mistakes during the streak plate method?

People normally forget to sterilize loop in between each division
Forget to cool down loop