Question

A peculiar odour found in marshy areas and cow sheds is of gas produced by :
A) Archaebacteria
B) Cyanobacteria
C) Slime moulds
D) Mycoplasma

Answer 1

Methanogens are prokaryotic microorganisms which produce methane as metabolic byproduct under hypoxic conditions, i.e. in low to no availability of oxygen.

Complete answer:
Methanogens present in marshy areas and in the animal gut like that of a cow, produce biogas from the dung of these animals.

Option A: Archaebacteria - Archaebacteria is a primitive group of bacteria. The three main groups of archaebacteria are - thermophiles, halophiles and methanogens. They produce marshy gas in the marshy areas and cow sheds, thus producing a peculiar odour.
Thus, this is the correct option.

Option B: Cyanobacteria or blue green algae, are bacteria, a few of which are nitrogen-fixing. They exist either freely or in a symbiotic relationship with plants or lichen-forming fungi. They grow naturally in marine and freshwater systems. They thrive in dams, rivers, reservoirs, lakes and even in hot springs.
Thus, this option is incorrect.

Option C: Slime moulds - They are saprophytic microorganisms which feed on decaying and dead organic matter. The term - slime - is because of the gelatine-like appearance of these slime moulds. They are usually found on the forest floors, soil, lawns, etc. This option is also incorrect.

Option D: Mycoplasma - Human and animal mycoplasma’s primary habitats are the mucous surfaces of the urogenital and respiratory tracts..
This also is an incorrect option.

Thus, the correct option is (A) Archaebacteria.

Note: Methanogens are anaerobic, obligate archaebacteria. They oxidise carbon dioxide during their cellular respiration, and produce methane as the waste product. They are found in the gut of termites, marshes, cattle rumen, sludges of sewage, etc.