Question

What is true for Actinomycetes?
A) They lack a cell wall.
B) They are the smallest living cells known.
C) They are filamentous Protists.
D) They are filamentous Monerans.

Answer 1

Monerans are prokaryotic organisms and include the most primitive of living forms. They generally possess a cell wall which contains peptidoglycan and polysaccharides other than cellulose. The cell has one envelope type of organization and lacks membrane bound organelles. DNA is naked in monerans. Some of the monerans have the ability to fix atmospheric nitrogen.

Complete answer:
The kingdom Monera includes all prokaryotic organisms, i.e., bacteria, archaebacteria, actinomycetes, cyanobacteria, mycoplasma and rickettsia.

Now let us discuss about Actinomycetes:
Actinomycetes are bacteria which have a tendency to form filaments. Some biologists consider them intermediate forms between bacteria and true fungi. They grow in the form of radiating colonies in cultures and, therefore, commonly called ray fungi. They are gram positive and occur most commonly in soil, freshwater, manure, food products and substrata rich in dead organic matter.

- All monerans have a cell wall except mycoplasma. So, it is not true that actinomycetes lack a cell wall.
- The smallest living cells known are mycoplasma. So, it is also not true about actinomycetes.
- The kingdom Protista contains diverse kinds of unicellular, eukaryotic microorganisms. So, it is not true for actinomycetes because they come under the monera kingdom.
- Yes, it is true about Actinomycetes that they are filamentous Monerans because they belong to the kingdom monera.

So, the correct answer is option (D) i.e, They are filamentous Monerans.

Note:
- Many actinomycetes resemble bacteria in their physiological activities. Therefore, they are considered as higher forms of bacteria.
- Actinomycetes are active soil decomposers. Many of them also produce antibiotics belonging to genus Streptomyces. The important antibiotics are – Streptomycin, Aureomycin, Chloromycin, Terramycin, Neomycin, Erythromycin. These antibiotics have proved very useful in combating several bacterial diseases in human beings.