Class Description
Actinomycetes They produce branching, multicellular filaments that resemble fungi. We obtain many valuable antibiotics from them.
Mycoplasmas They have lost their cell walls and are the smallest living cells (0.1-0.25 Ám); live as parasites in plant or animal cells; cause one kind of human pleumonia and many animal diseases.
Spirochetes They have spiral shape, with a distinctive set of flagella, called axial filaments; parasitic ones include those that cause syphilis, yaws, and Lyme disease.
Rickettsiae Tiny parasitic bacteria that usually live inside other cells; carried by ticks or insects and trasmitted to mammals by bites; cause diseases such as typhus (from lice) and Rocky Mountain spotted fever (from ticks).
Cyanobacteria Blue-green bacteria; photosynthetic; may form filamentous or clustered colonies; some colonies show division of labor: spore-producing, attaching, etc.

Kingdom Monera
Life on Earth