Light micrograph of purple bacteria from a sulphuretum. The bottom of this small water body is permanently anaerobic due to the decaying plant inputs, and in this milieu there is a society of predominantly anaerobic microorganisms that reduce or oxidise sulphur. Such an ecosystem is called a sulphuretum. The picture shows a colony of purple bacteria, probably belonging to the genus Thiocapsa, recognisable by its purple colour. Microscopic contrast method : dark field. Magnification 220x at a print width of 10 cm.