organisms that typically reproduce by asexual budding or fission and whose nutritional mode is absorption or photosynthesis or chemosynthesis

in some classifications considered a kingdom

archaebacteria found in anaerobic environments such as animal intestinal tracts or sediments or sewage and capable of producing methane; a source of natural gas

archaebacteria requiring a salt-rich environment for growth and survival

archaebacteria that thrive in strongly acidic environments at high temperatures

in some classifications considered a kingdom