Question

A few days after you have completed the streak plate method, you observe not one single isolated colony on the TSA plate. Explain why this may have happened.

How does dental plaque form?

How does tooth decay occur?

Answer 1

Answer: Streak plate method is done to isolate a specific microorganism from a mixed colony. Microbes often seem in isolated forms. Otherwise, they tend to be in a mixture of microbes. Streak plate enables the individual cells to colonize.
# TSA( Tryptone Soya Agar) is a medium used to the culture of bacteria. They are the general-purpose medium which is non-selective, providing nutrients for a wide variety of microbes.
# Sometimes, the streak plate method couldn't give isolated single colonies. There are many reasons for this. Some of them are;
° The TSA medium allows for a wide range of bacteria to grow. This causes numerous species of bacteria to grow together. Thus single colony can't be obtained.
° The streak plate allows the abundant cell to colonize in the last lines, as each streak causes a reduction in the inoculum. If more than one species is abundant, they can grow together.
° If the culture is allowed to grow for more days, the colonies will grow and isolated colonies can't be obtained.
° The major reason for not getting a single colony is contamination. It can occur due to personal errors, exposure of plates, or due to medium contamination. Contamination causes the growth of unwanted bacterias and fungus on the plate. Thus single isolated colonies can't be obtained.

How dental plaques are formed?
Answer: Dental plaques are biofilms produced over the surface of teeth which consists of oral bacteria, food particles, leukocytes, cell disintegrates, etc.. They are usually hard, colorless, or pale yellow colored which can adhere to teeth. They are matrix enclosed bacterial population which can adhere to the tooth surface. It is caused by a variety of bacterial species especially streptococcal species.
They make use of the nutrients in the food remains in the oral cavity to colonize. That's why brushing is important as it brushes off the food remains and bacteria.

Dental plaque can be divided into supragingival and subgingival plaques. Untreated dental plaques can lead to tooth decay and tooth loss.

How tooth decay occurs?
Answer: Tooth decay occurs due to the deposition of acid in teeth and mineral loss followed by it. The deposition of acid occurs when the sugar from the food particles remains in mouth and bacteria break down these sugars. Bacteria present in the plaque are thus dangerous this way. The acids cause the softening of the enamel and eventually cause a cavity. This causes tooth decay.
Thus dental plaque and tooth decay are directly connected. Proper oral hygiene is a preventive measure to avoid both.