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DATE: 17/18/2022
EXPERIMENT NO: 1
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Usually the dilution
factor at each step is constant, resulting in a geometric progression of the concentration
in a logarithmic fashion
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So, by calculating the total dilution over the
entire series
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In natural habitats,
bacteria usually grow together in populations containing a number of species
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Spread plate technique is the method of isolation of microorganisms and its
enumeration in a mixed culture and distributing it evenly over the surface of a medium
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In this technique a
small volume of dilutes bacterial mixture is transferred to the center of an agar plate
and evenly spread over the surface with a sterile L- shaped glass rod
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After incubation some of the
dispersed cells develop into isolated colonies
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The plate
needs to be dried at room temperature, so that the agar can absorb the bacteria more
readily
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After incubation the general form of the
colony and the shape of the edge or margins can be determined by looking down at the
top of the colony
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It is used to calculate the concentration of cells in the tube from which the
sample was plated
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LIMITATIONS OF SPREAD PLATE TECHNIQUE
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Strict aerobes are favored while microaerophila tend to grow slower

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Crowding of colonies make the enumeration difficult
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Master dilution is prepared by dissolving (1g) in 100 ml saline
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2
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3
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The pipette is discarded
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4
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The pipette is
discarded
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5
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The
pipette is discarded
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6
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The glass rod is removed from the beaker , passed through
the Bunsen burner flame with bent portion of rod, pointing downwards
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The rod is cooled for 10-15 seconds
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With the pipette labeled as 10-3, 0
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The petri plate is spun manually and the culture is spread uniformly with
a bent rod in the petri plates by moving the bent rod black anf forth
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Similarly 0
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10
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The plates were incubated in an inverted position for 24
hours at 37° C
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The result was observed in order to enumerate the bacterial colonies
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Isolated colonies

RESULT:

Isolated colonies were obtained after performing spread plate technique
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Number of colonies formed in the given sample =114*104 CFU/mL
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