When decaying organic matter sinks to the bottom of a lake or ocean, methane is produced as the biomass is broken down. Some of the methane is released from the surface into the atmosphere, where it acts as a potent greenhouse gas, while some is broken down by microorganisms in the water column. In a new study, an international research group reports that, as well as the “classical” methane consumers, filamentous bacteria of the genus Crenothrix – previously little studied in the environment – are also involved in the methane removal process.