Answer:
Methanogens
Step-by-step explanation
Archaea is one of the three major domains of living organisms. It contains single celled organisms that lack membrane bound organelles hence they are prokaryotes.
Methanogens are archaea that frequently inhibit the guts of animals that consume foods rich in cellulose such as cows.They breakdown the cellulose releasing marsh gas as a waste product.
They also live in anaerobic muck in wetlands.