They decompose plant and animal residues, synthesize humus, cycle nutrients such as carbon and nitrogen. The chemical by-products of microbial reactions bind together soil particles into stable aggregates that resist erosion. A special kind of fungus called Mycorrhizae invades plant root cells and aid in transfer of soil nutrients and water into the plant. Although not directly associated with plant roots actinomycetes and algae are also important fixers of atmospheric nitrogen that can used later by soil organisms. Not all microorganisms are beneficial.
Some organisms are harmful to plants and humans.
The survival of life on our planet depends on ultimately on the cooperation and interactivity of the various organisms. Especially important is the so called food chain or more accurately the food web. Energy is passed down the food chain from the primary producers such as plants to primary consumers such as ruminant animals to secondary and tertiary consumers which are predators. The body of one organism becomes food for another in a very complex interaction. Many organisms will die as the soil is removed and dries out while others such as insects worms and mammals may escape the sampling process.