ABSTRACT
Yeasts, fungi, protozoa and most bacteria, are heterotrophic organisms which means that the organisms need organic material to provide organic carbon required for growth. The remaining protists, algae and some groups of bacteria, obtain their organic carbon required for growth from inorganic carbon, namely carbon dioxide. Bacteria ‘ruled’ the earth for almost 2 billion years, spanning a period from about 3.5 billion years ago to about 5 billion years ago, when the first eukaryotes such as yeasts and fungi are supposed to have appeared on our planet for the first time. Eukaryotes are cells in which the genetic material, unlike bacteria, is contained in a distinct nucleus, which is surrounded by a membrane. The most important physical and chemical properties of a soil are determined by the amount and composition of soil organic matter and by the mineralogical composition, in which both the amount and composition of clay plays a dominant role.
