Compost heap bacteria. Coloured scanning electron micrograph of a dividing spirochaete amongst other bacteria from a compost heap. Compost is made by stacking together vegetable trimmings, non-seeding weed plants and grass cuttings in a heap. The material is broken down and the resulting brown crumbly compost is used to enrich the soil. Some saprophytic bacteria playing an important role in this degradation of plant remains are shown here (pink and green). At centre (green, corkscrew- like) is a spirochaete, with its characteristic spiral shape. The organism's centre line shows that it is in the process of reproducing itself by division. Magnification: x5,000 at 6x6cm size.