Aerobic methane-oxidizing bacteria (methanotrophs) have a key role in the global carbon cycle, converting methane to biomass and carbon dioxide. Although these bacteria have been isolated from many environments, until recently, it was not known if they survived, much less thrived in thermoacidic environments, that is, locations with pH values of approximately 1 and temperatures greater than 50 degrees C. Recently, three independent studies have isolated unusual methanotrophs from such extreme environments, expanding the known functional and phylogenetic diversity of methanotrophs.