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Microbiology: a very short introduction

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



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