Pure culture can be prepared from a mixture of cultures by using the streak plate method. This enables the bacterial cells to be diluted to obtain a pure culture after many-folds dilution.
Pure culture is the one in which only one species, strain or clone of bacteria are grown. The pure culture enables to scientists to study in detail about its anatomy, lifestyle and potential uses or harms, without the interference of any other microbe.
Streak-plate method is the most commonly used technique in microbiology labs to isolate a single type of bacteria. It is performed by creating the smears of bacteria in zig-zag motion to dilute its concentration.
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Answer:
Paul has natural active immunity, while Nicholas has artificial active immunity.
Explanation:
Natural active immunity is an immunity that occurs when an individual is exposed to a disease causing organism, gets infected, and also become immune to the disease due to the primary immune response. From the question, Paul has natural active immunity because he had chicken pox before, and the virus that causes chicken pox has interacted with his immune response, hence, making him to develop natural immunity to the disease.
Artificial active immunity is an immunity that an individual acquires when small amount of immunity to a disease is deliberately exposed to his body. Artificial active immunity is usually produced in the form of vaccinations. From the question, Nicholas has artificial active immunity because chicken pox vaccines were intentionally introduced to his body.