7/21/2019 Ubiquity of Microorganisms(1)
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Ubiquity of Microorganisms
I. Introduction
Microorganisms are found in nature either in their substrate or
as aerial contaminants. In
conditions where their food and environmental needs are properly
met, they actively proliferate.However, when food or environmental
factors become limiting, their growth may be arrested.
Under severe conditions they may ultimately die.
II. Materials and Methods
Materials:
Prepoured nutrient agar !"#$ plates !% per group$
& piece paper mold with a %' cm% cut at the center
(.& ) sterile peptone water in test tube
% pieces sterile cotton swabs
*( ) ethanol
+etergent
unsen burner or alcohol lamp
Procedure
&. -roups of most students for each shall do the
following:
a$ /0pose open plates to the air inside and outside the
laboratory for ' minutes
b$ 1ouch agar surface with finger tips before and after running
fingers through hair
c$ 1ouch agar surface with finger tips before and aftr washing
hands with detergent
d$ 2pread &% drops of tap watr on the agar surface by
swirling the plate, and scatter fine soil
particles on the surface of another agar plate.%. Incubate
plates in an inverted position inside a plastic bag for %3 hours at
room temperature or
at *45.
III. 6esults
2pecies
7orm /levation Margin 5olor "umber
2pecies &
2pecies %
2pecies
2pecies 3
2pecies '
2pecies 8
&. 5ompare the relative abundance of growth on the
plates.
%. 2elect isolated colonies from the growth and characteri9e
based on type of margin, elevation,
te0ture and color.. /ach student selects a colony to purify for
/0ercise 3.
