Light micrograph of a Paramecium bursaria ciliate and a purple bacteria colony, probably belonging to the genus Thiocapsa. Paramecium bursaria harbours many symbiotic green algae of the genus Chlorella. Contrasting with the green of the protozoa are the purple bacteria with their red colour. Some filamentous cyanobacteria can be seen among the microorganisms. Microscopic contrast method : Differential interference contrast. Magnification 500x at a print width of 10 cm.