Question

Usnic acid is an antibiotic obtained from
A. Fungi
B. Bacteria
C. Lichen
D. Algae

Answer 1

Hint: Usnic acid is a yellow crystalline compound. It is an antibiotic compound which means that it kills the bacteria or hinders the growth of bacteria. They are obtained from symbiotic associations of fungus and algae. These symbiotic units are found attached to the bark of the trees.

Complete answer:
An antibiotic is a substance that inhibits the growth of the bacteria or directly kills the bacteria. Usually, many fungi species are identified which have antibiotic properties. For example, penicillin is obtained from a fungus and it is a wide range antibiotic that kills many bacterial species. Except for fungus, many species of lichens are also reported to synthesize antibiotic compounds like usnic acid. Usnic acid is a yellow crystalline acidic compound having molecular formula \[{{C}_{18}}{{H}_{16}}{{O}_{7}}\]. It is a naturally occurring antibiotic that is found in many lichen species. The lichens are the symbiotic associations of fungi and algae. These are found growing over barks of trees, stone surfaces, rotting materials, etc. they stay attached to the substratum. Both fungi and algae benefited from this association. They secrete many compounds including antibiotics to sustain their safe development. The usnic acid was found to be synthesized by various lichen species namely Usnea, Cladonia, Alectoria,, etc. It is believed that usnic acid in lichens is used to protect them from the harmful effects of sunlight. It is a secondary metabolite of lichens. This means that it is a waste type secretory product of lichens. Also, the bitter taste of usnic acid protects the lichens from grazing animals.
Hence, from the above discussion, we can conclude that the right answer is option C.

Note: Many fungal and lichen species secrete antibiotics naturally. The use of antibiotics in the pharmaceutical industry has saved millions of lives from deadly bacterial infections. But due to the un-sustained use of antibiotic medicines, the bacteria have become resistant to them. This is called antibiotic resistance. This causes a greater threat to future health emergencies. Thus, alternatives need to be found.