Deep-sea mussels from cold seeps and hydrothermal vents were studied to understand their tissue-associated bacteria. The researchers looked at different tissues of two mussel species and found that the gill had a unique bacterial community related to methane oxidation. The adductor muscle, mantle, foot, and visceral mass had different bacteria in mussels from cold seeps compared to hydrothermal vents. The gill communities were similar between the two environments, while other tissues showed variations. This study helps us learn more about the bacteria living in deep-sea mussels from different habitats.