Monera is a kingdom composed solely of prokaryotic organisms like bacteria and cyanobacteria. Bacteria can exist as single cells, filaments, or colonies, and can be aerobic or anaerobic, autotrophic or heterotrophic. Other groups in the kingdom include cyanobacteria, which can perform photosynthesis, and eubacteria, which rely on organic carbon sources. Archaebacteria are the most ancient group and differ so greatly from other Monera that they may constitute their own kingdom.