Test: Microorganisms Friend & Foe- 1 - Class 8 MCQ

• Nitrogen-fixing bacteria are responsible for fixing atmospheric nitrogen into the soil.
• This process enriches the soil with nitrogen, which is essential for plant growth.
• These bacteria often reside in the root nodules of leguminous plants and contribute significantly to soil fertility.

Pasteurization is a process in which milk is heated to about 70oC for 15 to 30 seconds and then suddenly chilled and stored. By doing so, it prevents the growth of microbes. This process was discovered by Louis Pasteur and hence is called pasteurization.

• Microorganisms like bacteria and yeast are used in making curd, bread, and cake.
• For example, the bacterium Lactobacillus helps in turning milk into curd by multiplying in it.
• Similarly, yeast is used in making bread by causing the dough to rise.

While baking cakes, yeast reproduces rapidly and produces carbon dioxide gas. This gas is responsible for the spongy texture of cake.

Common salt is used to preserve meat and fish to stop bacteria from growing on them. Bacteria can make food go bad and make us sick. So, by using salt, we can keep the meat and fish fresh for a longer time. It acts like a shield to protect our food from getting spoiled.

Sugar in food preservation reduces the wetness (moisture) which helps to stop the bacteria from growing.

Lactobacillus is the microorganism present in curd. This bacterium converts milk into curd at 30 to 40oC.

Antibiotics are medicines that kill or stop the growth of disease-causing bacteria. They are used to cure various diseases and infections. It is important to take antibiotics only when prescribed by a doctor and to complete the full course.

Yeast is used for the production of alcohol and wine by the process of fermentation.

Tuberculosis: Tuberculosis is a bacterial infection caused by the bacterium Mycobacterium tuberculosis. It primarily affects the lungs but can also affect other parts of the body. 

- Vaccines are used to prevent diseases.
- Vaccines work by stimulating the immune system to recognize and fight specific pathogens, like viruses or bacteria.
- They contain weakened or inactive parts of a particular organism that trigger an immune response.
- This prepares the body to recognize and combat the pathogen if exposed in the future.
- They do not cure diseases.
- Curing implies treating an active disease, which is not the purpose of vaccines.
- Vaccines do not cause diseases.
- While mild symptoms may occur, they do not cause the disease they prevent.