The process where bacteria break down organic matter in the absence of oxygen is called anaerobic decomposition. This microbial action occurs in environments where oxygen is limited or absent, such as in wetlands or deep ocean floors. Anaerobic bacteria convert organic material into gases, such as methane and carbon dioxide, and other substances. While less efficient than aerobic decomposition, anaerobic processes are vital for nutrient cycling and contribute to the formation of natural resources like natural gas.