Polarised light micrograph of diatom, euglenoid and purple bacteria. Euglenoids are flagellate microorganisms, that have a flexible body. They possess the characteristic features of plants and animals. There are around 1000 species of Euglena found. Diatoms are single-celled photosynthetic algae, of which there are about 100,000 species. They have mineralised cell walls (frustules) that contain silica and provide protection and support. Purple bacteria are gram-negative proteobacteria that use photosynthesis to produce their own food. Magnification: 186x when printed 10 centimetres wide.