What is the Difference Between Methanogens and Methanotrophs

The main difference between methanogens and methanotrophs is that methanogens are microorganisms producing methane as a metabolic byproduct whereas methanotrophs are prokaryotes metabolizing methane as the only carbon source of energy. 

Methanogens and methanotrophs are two types of microorganisms with methane-related metabolism. Furthermore, methanogenesis occurs in low oxygen concentrations while methanotrophs use oxygen to oxidize methane.

Key Areas Covered

1. What are Methanogens
     – Definition, Features, Importance
2. What are Methanotrophs
     – Definition, Features, Importance
3. What are the Similarities Between Methanogens and Methanotrophs
     – Outline of Common Features
4. What is the Difference Between Methanogens and Methanotrophs
     – Comparison of Key Differences

Key Terms

Anoxic, Denitrification, Methane, Methanogens, Methanotrophs, Oxic

What are Methanogens

Methanogens are a group of microorganisms that produce methane. The production of methane occurs as a metabolic byproduct under hypoxic conditions. Also, most methanogens belong to the domain Archaea. These methanogens mainly grow in wetlands, contributing to marsh gas, which is a mixture of methane, hydrogen sulfide, and carbon dioxide. In addition, methanogens live in the digestive tracts of ruminants as well as humans. Methanogens can also grow in sewage digesters, groundwater, and soil. On the other hand, extremophiles, which live in hot springs and hydrothermal vents also produce methane.

Figure 1: Methanogenesis

Furthermore, methanogenesis refers to the process that produces methane by methanogens. Here, hydrocarbons are broken down to produce carbon dioxide and methane as byproducts. Generally, methanogenesis is strictly an anaerobic process and methanogens can be poisoned by the presence of oxygen.

What are Methanotrophs

Methanotrophs are another group of microorganisms that oxidize methane as their main carbon source in order to produce energy. Furthermore, methanotrophs commonly grow near environments where methanogenesis occurs; for example, oceans, mud, marshes, underground environments, soils, rice paddies, and landfills. Also, they can grow either aerobically or anaerobically. Under aerobic conditions, they oxidize methane into formaldehyde, which is then incorporated into organic compounds through biochemical pathways, assimilating carbon.

Figure 2: Methylococcus capsulatus

However, based on the pathway of assimilating carbon, methanotrophs can be classified into two groups as Methylococcaceae or type I methanotrophs and Methylocystaceae or type II methanotrophs. Here, type I methanotrophs use the RuMP pathway to assimilate carbon while type II methanotrophs use the serine pathway of carbon assimilation. On the other hand, anaerobic methanotrophs that live in marine habitats and freshwater sediments undergo reverse methanogenesis coupled with either denitrification or sulfate reduction.

Similarities Between Methanogens and Methanotrophs

• Methanogens and methanotrophs are two types of microorganisms whose metabolism is related to methane.
• They mainly grow in the soil.
• Also, in the metabolism of both organism, methane is the second most important greenhouse gas after carbon dioxide.
• Both types of microorganisms contribute to biological methane cycle by oxidizing and producing methane in the soil.

Difference Between Methanogens and Methanotrophs

Definition

Methanogens refer to any methane-producing bacteria, especially archaea that reduce carbon dioxide to methane, while methanotrophs refer to any group of aerobic bacteria capable of utilizing methane as a carbon and energy source. Thus, this is the main difference between methanogens and methanotrophs.

Fate of Methane

Another important difference between methanogens and methanotrophs is that the methanogens produce methane while methanotrophs oxidize methane.

Influence of Oxygen

Furthermore, one other difference between methanogens and methanotrophs is that methanogens are active anoxic conditions while methanotrophs are active in oxic conditions.

Importance

While methanogens produce methane, which is a greenhouse gas, methanotrophs help to reduce the effect of methane. Hence, this is also a difference between methanogens and methanotrophs.

Conclusion

Methanogens are the methane-producing microorganisms in the soil. Significantly, methanogens are active in anoxic conditions. In contrast, methanotrophs are the microorganisms that use methane as their carbon source. They use oxygen to oxidize methane in order to produce energy. Both methanogens and methanotrophs play a key role in the methane cycle. However, the main difference between methanogens and methanotrophs is their effect on methane and type of oxygen condition in which they are active.

References:

1. Vance, D. B., “ NATURAL ATTENUATION PART V: METHANOGENIC SYSTEMS.” 2 The 4 Technology Solutions, Available Here.

Image Courtesy:

1. “CSIRO ScienceImage 1898 Testing Sheep for Methane Production” By CSIRO (CC BY 3.0) via Commons Wikimedia 
2. “Methylococcus capsulatus” By (Image: Anne Fjellbirkeland) – The Genome of a Methane-Loving Bacterium. PLoS Biol 2/10/2004: e358. (CC BY 2.5) via Commons Wikimedia