Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes with the help of a microscope, which sample would you carry and why?
I would carry a sample of curd from my home to the biology laboratory. Curd contains millions of Lactobacillus bacteria, commonly called lactic acid bacteria (LAB), which can be easily observed under a microscope.
According to the context, microbes are present everywhere – in soil, water, air, and inside our bodies. During curd formation, LAB grow in milk and produce acids that coagulate and partially digest the milk proteins. A small amount of curd added as inoculum contains millions of these beneficial bacteria.
This sample is ideal because it is easily available at home, contains a high concentration of microbes, and the bacteria can be clearly demonstrated under a microscope in the laboratory for study purposes.
Explanation
This question is from NCERT Biology Class 12, Chapter 8 (Microbes in Human Welfare). The textbook explains that curd is an excellent source of lactic acid bacteria (LAB), specifically Lactobacillus. The context states that 'A small amount of curd added to the fresh milk as inoculum or starter contain millions of LAB.' This makes curd an ideal sample to carry from home as it is readily available and contains abundant microbes that can be easily observed under a microscope.
Solution Steps
Step 1: Identify samples mentioned in context that contain microbes - curd, soil, water
Step 2: Select the most practical and microbe-rich sample - curd contains millions of LAB
Step 3: Explain why curd is suitable - easily available, contains Lactobacillus bacteria in high concentration