Sem-5 Practical Workshop Quiz

When isolating Rhizobium from root nodules, which step is crucial to ensure only nodule-specific bacteria grow?

• Use selective media for isolation.
• Isolate bacteria from soil samples instead.
• Use non-selective media for isolation.
• Incubate at room temperature without any media.

Why is Pikovskaya’s agar commonly used for isolating phosphate-solubilizing microorganisms?

• Pikovskaya’s agar is used for isolating bacteria that produce antibiotics.
• Pikovskaya’s agar contains high levels of nitrogen to promote microbial growth.
• Pikovskaya’s agar is used for isolating phosphate-solubilizing microorganisms because it contains tricalcium phosphate, which these microorganisms can solubilize.
• Pikovskaya’s agar is primarily used for isolating fungi from soil samples.

Why do colonies of Azotobacter appear slimy and mucoid on Ashby’s medium?

• The colonies produce extracellular polysaccharides that create a slimy, mucoid texture.
• The colonies are contaminated with other bacteria.
• The colonies are grown at too high a temperature.
• The colonies lack sufficient nutrients for growth.

In a practical experiment, how would you test the efficiency of biofertilizer-treated seeds?

• Conduct a controlled experiment comparing growth metrics of biofertilizer-treated seeds with untreated seeds.
• Observe the color of the seeds after treatment.
• Count the number of seeds in each treatment group.
• Measure soil pH levels before and after planting seeds.

What is the significance of a clear zone around colonies grown on Pikovskaya’s agar?

• The clear zone signifies phosphate solubilization by the bacteria.
• The clear zone represents antibiotic resistance.
• The clear zone shows the presence of toxins.
• The clear zone indicates bacterial growth rate.

In the Methylene Blue Reduction Test, what does faster decolorization of methylene blue indicate about the quality of milk?

• Faster decolorization indicates lower quality of milk.
• Faster decolorization indicates higher quality of milk.
• Faster decolorization has no effect on milk quality.
• Faster decolorization suggests the milk is fresh.

During the Standard Plate Count (SPC) method for milk microflora, why is it necessary to perform serial dilutions?

• To accurately count and enumerate microorganisms in a sample.
• To enhance the flavor of the milk during testing.
• To reduce the volume of the sample being tested.
• To increase the temperature of the milk sample.

During the determination of a standard curve for reducing sugar using the DNS method, why is 3,5-dinitrosalicylic acid (DNS) used?

• DNS is used because it is a strong acid that enhances sugar solubility.
• DNS is used to stabilize the sugar solution during the experiment.
• DNS is used as a preservative for the sugar samples.
• DNS is used because it reacts with reducing sugars to produce a measurable color change.

What is the purpose of boiling the sample with DNS in the DNS method for reducing sugar estimation?

• To sterilize the sample before testing.
• To dilute the sugars for easier measurement.
• To separate the sugars from other components in the sample.
• The purpose of boiling the sample with DNS is to facilitate the reaction between DNS and reducing sugars to form a measurable colored complex.

During the immobilization of yeast cells using sodium alginate, why is calcium chloride solution used?

• Calcium chloride is used to dissolve sodium alginate.
• Calcium chloride is used to enhance yeast fermentation.
• Calcium chloride is used to provide nutrients to yeast cells.
• Calcium chloride is used to cross-link sodium alginate, immobilizing yeast cells.