Gram-positive bacteria, blue-green algae and extremophiles are some examples of Monerans. Currently, most scientists divide the former Moneran kingdom into two separate kingdoms: Archaebacteria and Eubacteria.
Archae and Eubacteria contain entirely prokaryotic organisms. Prokaryotes are organisms with cells that have no nucleus or membrane-bound organelles. However, most do contain ribosomes. Prokaryotes are unicellular and obtain nutrients as material diffuses across their outer cellular membranes. Archaebacteria are mostly extremophiles, organisms capable of surviving in conditions that are inhospitable to most life.
Archae includes organisms that obtain energy from sulfur and methane and those that thrive in hot springs or near thermal vents in the ocean. These organisms are important in recycling chemicals such as nitrogen, carbon and sulfur for reuse in the environment. Eubacteria, or true bacteria, are those bacterial organisms responsible for many of the world's diseases. Eubacteria also make up the vital internal fauna necessary for the survival of many animals, are important in the production of medicine and are useful in the fermentation of various food products.
Cyanobacteria, or blue-green algae, are also members of Eubacteria. Cyanobacteria obtain energy through photosynthesis and are important producers of oxygen. Other cyanobacteria produce dangerous neurotoxins that pose a risk to other aquatic species during times of excessive algal blooms and to humans who eat fish from such environments.