Isolation of Pure Cultures by Dilution Techniques and Gram Staining Method
Isolation of Pure Cultures by Dilution Techniques and Gram Staining Method
Results
Table 1. Gram stain reaction and cellular features of the culture.
Gram staining methods were applied on the given mixture of Bacillus cereus,
Escherichia coli and Staphylococcus aureus and then examined microscopically. Results were recorded in Table 1.
Gram Reactions Cell shapes Cell Ends and Arrangement Size Distinctive Characters Predicted Bacteria
Bacteria 1 Gram positive (purple) Cocci Rounded, clusters, singly Small - Staphylococcus aureus
Bacteria 2 Gram negative (pink) Rods (shorter than B. cereus) Rounded, regular, pair, clusters Medium - Escherichia coli
Bacteria 3 Gram positive (purple) Long rods Rounded, irregular, groups, chains Large Endospores present; spherical, central, not distending the cell Bacillus cereus
Table 2. The observation of the colonies on the nutrient agar plates after incubated
Three isolation techniques were used; streak plate, spread plate and pour plate and the agar plates were then inverted and incubated at 370C for one day. The distributions of colonies were then observed. Observations were recorded.
Isolation Techniques Observation on the nutrient agar plates
Streak plate At the first inoculum, all the bacterial colonies were overlapping with each other and it was difficult to distinguish the colonies. At the 4th and 5th inoculum, it was easier to distinguish the colonies as they grew apart from each other. The appearance of each colony type could be determined at the final inoculum.
Spread plate The colonies were distributed evenly over the surface of the nutrient agar but there were more overlapping of colonies. Bacterial colonies could still be distinguished from each other.
Pour plate Some bacterial colonies are embedded in the agar medium and they are much smaller than those found on the surface. Bacterial colonies were difficult to distinguish from each other.
Table 3. The descriptions of the
Results
Table 1. Gram stain reaction and cellular features of the culture.
Gram staining methods were applied on the given mixture of Bacillus cereus,
Escherichia coli and Staphylococcus aureus and then examined microscopically. Results were recorded in Table 1.
Gram Reactions Cell shapes Cell Ends and Arrangement Size Distinctive Characters Predicted Bacteria
Bacteria 1 Gram positive (purple) Cocci Rounded, clusters, singly Small - Staphylococcus aureus
Bacteria 2 Gram negative (pink) Rods (shorter than B. cereus) Rounded, regular, pair, clusters Medium - Escherichia coli
Bacteria 3 Gram positive (purple) Long rods Rounded, irregular, groups, chains Large Endospores present; spherical, central, not distending the cell Bacillus cereus
Table 2. The observation of the colonies on the nutrient agar plates after incubated
Three isolation techniques were used; streak plate, spread plate and pour plate and the agar plates were then inverted and incubated at 370C for one day. The distributions of colonies were then observed. Observations were recorded.
Isolation Techniques Observation on the nutrient agar plates
Streak plate At the first inoculum, all the bacterial colonies were overlapping with each other and it was difficult to distinguish the colonies. At the 4th and 5th inoculum, it was easier to distinguish the colonies as they grew apart from each other. The appearance of each colony type could be determined at the final inoculum.
Spread plate The colonies were distributed evenly over the surface of the nutrient agar but there were more overlapping of colonies. Bacterial colonies could still be distinguished from each other.
Pour plate Some bacterial colonies are embedded in the agar medium and they are much smaller than those found on the surface. Bacterial colonies were difficult to distinguish from each other.
Table 3. The descriptions of the