Test: Microorganisms Friend & Foe- 1 - UPSC

Microbiology is the study of all living organisms that are too small to be visible to the naked eye.
This includes bacteria, archaea, viruses, fungi, prions, protozoa, and algae, collectively known as 'microbes'. 

Leeuwenhoek observed a large number of living microorganisms in a drop of water when observed under the microscope. These organisms are not visible by naked eyes.

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

• Rhizobium is a bacteria found in soil that helps in fixing nitrogen in leguminous plants. It attaches to the roots of the leguminous plant and produces nodules.
• These nodules fix atmospheric nitrogen and convert it into ammonia that can be used by the plant for its growth and development.
  

Animals or insects carry infecting agents from a sick person to another potential host. These animals are thus the intermediaries and are termed as vectors.
The most common vectors are mosquitoes.

Option A: Salt is effective as a preservative because it reduces the water activity of foods. Adding salt to foods can also cause microbial cells to undergo osmotic shock, resulting in the loss of water from the cell and thereby causing cell death or retarded growth.
Option B: Drying or “dehydrating” food is a method of food preservation that removes enough moisture from the food so bacteria, yeast, and molds cannot grow.
Option C: Boiling or blanching food at high temperatures destroys all enzyme activity and almost all microorganisms. The more acidic the food, such as fruit, the more easily microorganisms are destroyed by heat. Boiled preserves must be sealed in airless conditions (e.g. airtight jars) to prolong their shelf life.
Option D: Pickling is defined as the process of preserving a food by either anaerobic fermentation in brine or immersion in vinegar. It can add a special flavor to food by itself or mixed in with other foods.

Thus, option E is correct.

Fermentation is the process in which yeasts convert sugar into ethanol in the absence of oxygen. The fermentation process is used to produce alcoholic beverages.

There are five major types of infectious agents:

• Bacteria
• Viruses
• Fungi
• Protozoa
• Helminths

In addition, a new class of infectious agents, the prions, has recently been recognized.

Microorganism and microbe are two words having the same meaning, very small organisms that cannot be seen with naked eyes.

 Citrus canker is a plant disease caused by bacteria. It’s mode of transmission is through air.