Spread-Plate Technique, Streak-Plate Technique
Abstract
Agar streak plates are essential in Microbiology; it allow bacteria as well as fungi to grow on a
solid surface to produce discrete colonies. Staphylococcus Aureus and E. coli are used in this
experiment to obtain well-isolated and pure colonies. Several techniques are used, which are the
streak, pour, and spread plate techniques. Pour-plate methods allow the innovative sample to be
diluted several times, which reduces the microbial population enough to obtain separate colonies
upon plating. Though the pour plate method was not used in this experiment. The streak-plate
technique causes the bacterial components to shift to the edge of an agar plate, using an
inoculating loop, and then streaks over the surface in several patterns. Spread-plates technique is
a procedure where a small volume of dilute bacterial mixture containing 100 to 300 cells or
fewer is transferred to the center of an agar plate. Then it is spread evenly over the surface with a
sterile L-shaped rod.
Introduction
The purpose of these techniques is to produce isolated colonies of an organism on an agar plate.
This is beneficial when there is a need to separate organisms in a mixed culture or a need to
study the colony morphology of an organism. The spread-plate technique is a direct way of
achieving these results. Through streaking, a diluted gradient is established on the surface of the
plate as cells are deposited on the agar surface. The isolated cells grow into colonies and can be
used to establish pure cultures. The surface colonies are circular and large, subsurface colonies
are lenticular or lens-shaped and much smaller.
Materials
Escherichia Coli Inoculating Loop Pipettes With
Pipettor
Staphylococcus Aureus 95% Ethyl Alcohol 3 Agar Plate
Bunsen Burner L-shaped Glass Rod Sharpie
Petri Plates 0.9% NaCl Saline
Procedure
1. Streak-Plate Techniques (T-Streak)
a. Take the sharpie and make a T-Streak plate a Continuous Plate and a Quadrant
Plate.
b. Take the Escherichia Coli and remove the cap place the inoculating loop and pick
some bacteria up.
c. Than start at area 1 and gently spread the inoculating loop of bacteria over a small
area in that section at one edge of the plate.
d. Remove the inoculating loop and kill any remaining bacteria by flaming them.
Then insert the loop under the lid and cool it at the edge of the agar near area 1.
e. Rotate the plate while carefully keeping in mind where the initial streaks end and
cross over the streak in area 1 to enter area 2.
f. Remove the inoculating loop, flame it, cool in the agar as before, and repeat the
streaking process for the area 3.
2. Continuous Plate
a. Place a line straight across the plate to divide it into two.
b. Take the Escherichia Coli and remove the cap place the inoculating loop and pick
some bacteria up
Abstract
Agar streak plates are essential in Microbiology; it allow bacteria as well as fungi to grow on a
solid surface to produce discrete colonies. Staphylococcus Aureus and E. coli are used in this
experiment to obtain well-isolated and pure colonies. Several techniques are used, which are the
streak, pour, and spread plate techniques. Pour-plate methods allow the innovative sample to be
diluted several times, which reduces the microbial population enough to obtain separate colonies
upon plating. Though the pour plate method was not used in this experiment. The streak-plate
technique causes the bacterial components to shift to the edge of an agar plate, using an
inoculating loop, and then streaks over the surface in several patterns. Spread-plates technique is
a procedure where a small volume of dilute bacterial mixture containing 100 to 300 cells or
fewer is transferred to the center of an agar plate. Then it is spread evenly over the surface with a
sterile L-shaped rod.
Introduction
The purpose of these techniques is to produce isolated colonies of an organism on an agar plate.
This is beneficial when there is a need to separate organisms in a mixed culture or a need to
study the colony morphology of an organism. The spread-plate technique is a direct way of
achieving these results. Through streaking, a diluted gradient is established on the surface of the
plate as cells are deposited on the agar surface. The isolated cells grow into colonies and can be
used to establish pure cultures. The surface colonies are circular and large, subsurface colonies
are lenticular or lens-shaped and much smaller.
Materials
Escherichia Coli Inoculating Loop Pipettes With
Pipettor
Staphylococcus Aureus 95% Ethyl Alcohol 3 Agar Plate
Bunsen Burner L-shaped Glass Rod Sharpie
Petri Plates 0.9% NaCl Saline
Procedure
1. Streak-Plate Techniques (T-Streak)
a. Take the sharpie and make a T-Streak plate a Continuous Plate and a Quadrant
Plate.
b. Take the Escherichia Coli and remove the cap place the inoculating loop and pick
some bacteria up.
c. Than start at area 1 and gently spread the inoculating loop of bacteria over a small
area in that section at one edge of the plate.
d. Remove the inoculating loop and kill any remaining bacteria by flaming them.
Then insert the loop under the lid and cool it at the edge of the agar near area 1.
e. Rotate the plate while carefully keeping in mind where the initial streaks end and
cross over the streak in area 1 to enter area 2.
f. Remove the inoculating loop, flame it, cool in the agar as before, and repeat the
streaking process for the area 3.
2. Continuous Plate
a. Place a line straight across the plate to divide it into two.
b. Take the Escherichia Coli and remove the cap place the inoculating loop and pick
some bacteria up
