Consider the following statements about microbes:
(A) Microbes are present even deep inside geysers (thermal vents) and deep in the soil.
(B) Bacteria and many fungi can be grown on nutritive media to form colonies that can be seen with the naked eyes.
(C) Prions are proteinaceous infectious agents.
(D) During growth in milk, Lactobacillus and related bacteria produce alcohols that coagulate and partially digest the milk proteins.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (B) and (C) only
Microbes are a very diverse group: protozoa, bacteria, fungi, microscopic plant and animal viruses, viroids and prions. They live almost everywhere, even in places where no other life can survive.
(A) Microbes are present even deep inside geysers (thermal vents) and deep in the soil. — True. Microbes live even at sites as hostile as thermal vents, deep in the soil, under thick snow and in highly acidic places.
(B) Bacteria and many fungi can be grown on nutritive media to form colonies that can be seen with the naked eyes. — True. A single microbe cannot be seen without a microscope, but a colony grown on nutritive media can. Such cultures help in the study of microbes.
(C) Prions are proteinaceous infectious agents. — True. Prions are infectious agents made of protein, and the book lists them among the microbes.
(D) During growth in milk, Lactobacillus and related bacteria produce alcohols that coagulate and partially digest the milk proteins. — False. Lactic acid bacteria (LAB) produce acids, not alcohols. The acids coagulate and partly digest the milk proteins and turn milk into curd.
NCERT Extract:
Microbes in Human Welfare – “… They are present even at sites where no other life-form could possibly exist–sites such as deep inside the geysers (thermal vents) where the temperature may be as high as 1000C, deep in the soil, under the layers of snow several metres thick, and in highly acidic environments. Microbes are diverse–protozoa, bacteria, fungi and microscopic animal and plant viruses, viroids and also prions that are proteinacious infectious agents. Some of the microbes are shown in Figures 8.1 and 8.2. Microbes like bacteria and many fungi can be grown on nutritive media to form colonies (Figure 8.3), that can be seen with the naked eyes.”
Microbes in Household Products – “… Micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB) grow in milk and convert it to curd. During growth, the LAB produce acids that coagulate and partially digest the milk proteins.”