Microbiology: a very short introduction
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FUNDAMENTALS OF
MICROBIOLOGY
CIVL270-Maraqa
Environmental Applications of
Microbial Processes
Wastewater treatment aerobic/anaerobic
Industry
Biocatalysts (enzymes)
Fermentation (cheese, yogurt, pickles)
Pharmaceuticals (antibiotics)
Bioremediation
Contaminated groundwater
Land-farming
Microorganism
Size (um)
Viruses
0.02-0.3
Bacteria
0.1-10
Some are pathogenic
Cholera, typhoid
Algae
1-100
Non pathogenic
Fungi
Few umseveral cm
Protozoa
10-300
CIVL270-Maraqa
Disease
All pathogenic
AIDS, hepatitis, mad cow
Many are nonpathogenic
Some are pathogenic
Amebic dysentery, malaria
CIVL270-Maraqa
Coliform as an Indicator
Total coliform
coliform
Total
Fecal
Fecal
Nonfecal
Nonfecal
Membrane Filter
Technique
CIVL270-Maraqa
35 oC
44.5 oC
Multiple-Tube Fermentation Technique
CIVL270-Maraqa
No. of tubes giving positive
reactions out of
MPN Index for
Coliform Counts by
the Multiple-Tube
Fermentation
Technique
MPN
index
5 of 10
ml each
5 of 1 ml
each
5 of 0.1
ml each
per 100
ml
4
3
1
33
4
4
0
34
5
0
0
23
5
0
1
31
5
0
2
43
5
2
1
70
5
3
1
110
5
3
2
140
5
3
3
180
5
4
0
130
5
5
5
>2400
In-Class Exercise
The membrane filter method is used to test a water for
coliform. Three different sample volumes (5, 50, and 200 ml)
were filtered through 3 membranes for each sample volume.
The number of colonies on each filter after incubation is listed
below. Find the number of coliforms/100 ml.
Solution:
Filter
#1
#2
#3
5-ml portion
4
8
5
50-ml portion
24
32
25
200-ml portion
101
128
144
Use the 50-ml portions since the counts fall between 20-80.
Average of 24, 32, and 25 is 27 coliform/50 ml.
In a 100-ml sample we have 27 x (100/50) = 54/100 ml.
CIVL270-Maraqa
In-Class Exercise
A multiple tube fermentation analysis of river water yielded the
following results. What is the MPN/100 ml of the water?
Solution:
Serial
dilution
Sample
portion (ml)
+ tubes
out of 5
0
1.0
5
1
0.1
5
2
0.01
2
3
0.001
1
4
0.0001
0
We choose 5-2-1.
From the MPN table we have 70/100 ml.
To account for dilution we have
70 (10/0.1) = 7000/100 ml of river water
