Lab 19 Goals and Objectives:
Exercise 21: Enumeration
Count colonies (30-300 plates) and share data
(Sample data/explanations in supplemental packet pages 69-72)
Exercise 58: Bacterial Counts on Foods
Plate pre-made dilutions for the following foods: meat, spinach, and milk
Use pre-poured solid plates and spread with beads
Each pair needs:
1:10 of each: meat, spinach, milk (no blending: done!)
1:1000 of each: meat, spinach, milk (no diluting: done!)
9 NA plates and 9 tubes of beads
Exercise 59: Bacteriological Examination of Water
If turbid, pre-filter water with cheese-cloth in funnel into new bottle
Each pair set up tubes for one water sample (you need minimum 200ml in your
sample for this exercise and Ex. 60)
Each pair needs:
5 DS lactose broth LARGE tubes
10 SS lactose broth normal tubes
Exercise 60: The Membrane Filter Method
Each pair use the same water sample from Exercise 59
Perform according to directions pg 403 except skip step 4, Filter 100ml of sample
Each pair needs:
Filter apparatus,
Grid filter disc, Absorbent pad,
Petri dish,
Endo MF broth
0.4
0.3
0.2
0.1
y = mx+b
2.55 X 105
3.4 X 106
CFU/ml
Once you can assign real CFU/ml numbers to the OD readings, you have
a standard curve and the equation of the line can be used to determine the
CFU/ml concentration in a sample from the OD reading
Fig 58.1
Dilutions
already made,
you just plate
Figure 59.1
Lab 19 Goals and Objectives:
Exercise 21: Enumeration
Count colonies (30-300 plates) and share data
(Sample data/explanations in supplemental packet pages 69-72)
Exercise 58: Bacterial Counts on Foods
Plate pre-made dilutions for the following foods: meat, spinach, and milk
Use pre-poured solid plates and spread with beads
Each pair needs:
1:10 of each: meat, spinach, milk (no blending: done!)
1:1000 of each: meat, spinach, milk (no diluting: done!)
9 NA plates and 9 tubes of beads
Exercise 59: Bacteriological Examination of Water
If turbid, pre-filter water with cheese-cloth in funnel into new bottle
Each pair set up tubes for one water sample (you need minimum 200ml in your
sample for this exercise and Ex. 60)
Each pair needs:
5 DS lactose broth LARGE tubes
10 SS lactose broth normal tubes
Exercise 60: The Membrane Filter Method
Each pair use the same water sample from Exercise 59
Perform according to directions pg 403 except skip step 4, Filter 100ml of sample
Each pair needs:
Filter apparatus,
Grid filter disc, Absorbent pad,
Petri dish,
Endo MF broth