3501906 Colony of Bacterium mallei, 1906 (litho) by German School, (20th century); Private Collection; (add.info.: Bacteria constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth\'s crust;); Prismatic Pictures .