This document discusses symbiotic relationships between bacteria and other organisms. It provides examples of bioluminescence in flashlight fish, pinecone fish, and lanternfish due to symbiotic bacteria. Bioremediation uses prokaryotes and fungi to detoxify polluted environments, such as lichen helping in oil spills. Methanogens are bacteria that live symbiotically in ruminant digestive systems like cows, producing methane as they break down cellulose.