MBS Lab Practical Exam Review

What is a pure culture?

A population of a single species/strain.

Ex: Soil slurge is not a pure culture because there’s multiple bacteria.

Ex: Four-phase streak plate is pure culture; the only way to make pure culture

Quadrant streaking steps

1. Sterilize inoculation loop

2. Spread bacteria onto ¼ of the plate

3. Sterilize inoculation loop again

4. Streak the loop through the ¼ into the 2/4 of the plate

5. Repeat

What are MAC plates

MAC plates are differential and selective because they look different on the plate and selective for something to grow.

Only gram-negative can grow on plates

What color is a lactose fermenter

Pink

What color is lactose non-fermenter

Yellow

What do bile salts in MAC plates

Inhibit the growth of Gram-positive bacteria

Red Biohazard

Large, throw out plates here

Orange Biohazard

Small, throw out microcentrifuge tubes, pipette, cuvettes, e. Coli paper towels, gloves, plates

What goes into the bleach bucket

Slides

What is the broken glass procedure?

• Spray bleach, let it sit

• Wipe up and discard paper towel in trash

• Clean up glass and put in broken glass bucket

Anaerobic Respiration

The process of generating ATP in the absence of oxygen

Aerobic Respiration

The process of converting nutrients into ATP in the presence of oxygen

Catabolite Repression; diauxic growth curve

Di = two glucose & lactose

Glucose is used first, then lactose.

B-gal is made AFTER lactose is used

What is conjugation

Horizontal gene transfer mechanism; direct cell-to-cell contact

Is kanamycin a donor or recipient

Donor

Is chloramphenicol a donor or recipient

Donor

Is myristic acid a donor or recipient

Recipient on the chromosome/DNA

Do donors or recipients have plasmids?

Donors

What are auxotrophs?

Something that loses the ability to make essential nutrients

Ex: kanamycin and cholera cannot make tryptophan, that’s why its auxotrophic

What are prototrophs

Something that can grow on a medium; it’s simple and defined

ex: bacteria like e. coli

Which is obligate anaerobe, obligate aerobe, and facultative anaerobe?

Lysogenic Cycle

Phage integrates DNA into bacteria, keeping the bacteria alive. Now, it’s a prophage, and the virus can continue to copy each time the bacteria divides.

Lytic cycle

Phage immediately multiplies once in the host.

Bacterial cell is lysed, and new phage is released.

How to do a serial dilution

1. Get 0.4ml (400 microliters) of the contents

2. Put into first tube along with 0.6ml TYE

3. Vortex/mix

4. Take out 100 microliters from tube 1.

5. Put 100 microliters of 10^0 into 900 microliters of TYE. This second tube is 10^-1

Spec Station

1. Blank machine with the blank cuvette by pressing the 0 ABS button

2. Take out the blank cuvette

3. Put in the new cuvette to get OBSERVED OD

4. Calculate OD by using the observed OD number and multiplying it by 10

What does 600nm measure on a spec?

Turbidity

Lag OD

Clear, not cloudy

Low OD: <0.3

Exponential OD:

Around 0.4

Stationary OD

Cloudy

High OD: >0.5

Micropipettes of a P20

Lower limit: 2

Upper limit: 20

ex: 125 = 12.5 microliters

Micropipettes of a P200

Lower limit: 20

Upper Limit: 200

Ex: 125 = 125 microliters

Micropipettes of a P1000

Lower limit: 200

Upper limit: 1000

Ex: 028 = 280 microliters or 0.28mL

Sequencing

TOP = 3’

BOTTOM = 5’

• 5’ ATCGCCAT 3’

  • G 3’

  • B

  • R

  • R
    Y

  • R

  • G

  • B 5’

What is aseptic technique

The transfer of culture from one medium to another to prevent contamination

Koch’s Postulates

Evidence that microorganisms as causative agents

1. Isolate bacteria from a diseased animal and grow it in pure culture

2. Put that cultured bacteria into a healthy animal

3. Reisolate it from the inoculated, diseased host

4. Find that it is identical to the original causative agent