Mcb Problem Set

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  • Topic: Water, Algae, Phytoplankton
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  • Published : February 11, 2013
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MCB 150 Lab
PROBLEM SET 1
1. The data below were obtained after performance of Ex. 2 as stated in your MCB 150 lab manual. a. Estimate the number of total bacteria, actinomycetes, fungi and algae per gram (dry weight) of soil collected from the IBS garden

pH: 6.0
ODW: 8.6 grams
Colony Counts:
PDA 10-1: 210, 190
AMA 10-4: 125, 119
SCA 10-4: 80, 62

10-2: 20, 34
10-5: 17, 29
10-5: 18, 2

Algal Medium (no. of + tubes/ no. of inoculated tubes):
10-1: 5/ 5
10-2: 5/ 5
10-3: 3/ 5
10-4: 1/ 5
10-5: 1/ 5
b. Potato Dextrose Agar used in the above exercise was compounded and supplemented with 50ppm of Rose Bengal and 100 ppm of Streptomycin. Compute for the amount of each component of this medium (exact volume used) considering that Rose Bengal is in powder and Streptomycin was given to you in stock solution of 100 µg per µl.

2. The data below were obtained after performance of Ex. 3 as stated in your MCB 150 lab manual. Determine the estimated number of bacteria and fungi per cubic feet of air collected from IBS parking lot using the impingement technique.

Capacity of vacuum source: 10 liters per minute
Sampling time: 28 minutes
Colony Counts:
PDA 10-1: TNTC, 210
PCA 10-1: 320, 230

10-2: 42, 90 10-3: 4, 12
10-2: 20, 10 10-3: 0, 0

10-4: 0, 1
10-4: 0, 1

3. The plankton counts below were obtained after collecting sea water sample 20 times using a plankton net (net mouth diameter: 20 cm, net length: 30 cm, arm length of sampler: 45 cm) via vertical towing and transferring the concentrated sample of 110 ml to 5% borax-buffered formalin at 1:9 ratio (water sample: preservative). Determine the estimated number of the said microorganisms in the sea water given the following counts:

a. using Sedgewick-Rafter tray (50 compartments, each with 1 mm width, of a single strip were observed) algae: 71
dinoflagellates: 126
diatoms: 28
Compute for the Simpson's Index of Diversity for the above plankton counts. b. using Haemocytometer (four square A...
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