Methanogens
மெத்தனோஜென்கள்
Do not confuse Methanogens with simple saprophytes. These are Archaebacteria, not Eubacteria. Their ability to thrive in anaerobic conditions is a metabolic masterclass that NTA tests repeatedly.
The idea
Methanogens are anaerobic bacteria that thrive on cellulosic material. They perform anaerobic respiration to produce methane, CO2, and H2. Methanobacterium is the standard NCERT example. They are found in the rumen of cattle and in anaerobic sludge during sewage treatment.
Why it matters
These bacteria exist to break down complex cellulose into simpler compounds, serving as a vital part of the digestive process in ruminants and the decomposition process in anaerobic environments.
NEET lens
NEET focuses on the location: rumen of cattle and sewage treatment plants. Remember they are Archaebacteria, not Eubacteria. Expect a matching question or a statement-based question regarding their gaseous output. Do not miss the 'anaerobic' keyword; it is the most common trap.
Clinical significance
In the human gut, methanogens like Methanobrevibacter smithii are linked to constipation and irritable bowel syndrome. An overgrowth disrupts the delicate balance of the human microbiome. Their metabolic output directly affects intestinal transit time.
Introduction
Methanogens are bacteria that grow anaerobically on cellulosic material and produce large amounts of methane along with CO2 and H2.
Core concept
Example: Methanobacterium. Methanogens are commonly found in the anaerobic sludge during sewage treatment and in the rumen (a part of the stomach) of cattle, where a lot of cellulosic material is present; they help break down cellulose and play an important role in cattle nutrition. Cattle excreta (dung), commonly called gobar, is rich in these bacteria and is used to generate biogas (gobar gas). Biogas is a mixture of gases (predominantly methane) produced by microbial activity and is used as fuel.
Go deeper
Methanogens belong to archaebacteria in the five-kingdom classification — they live in extreme, oxygen-free conditions such as marshy areas and animal guts.
From Class 10
Cow dung contains bacteria that make methane gas, which can be burnt as fuel in a gobar gas plant.