Commensalism is common and is a significant factor in organism succession within microbial communities. An example is S. cerevisiae releasing riboflavin for use by L. casei for growth. Prior modification of the environment by one organism often leads to better growth for another organism. Examples of environmental changes include the removal of oxygen for anaerobic processes, raising the water content, reducing the osmotic pressure and detoxifying the environment. This process is called metabiosis and is used for the production of the Japanese drink sake.
Competition is the single most important interaction in nature.
Experiments have shown that some or all of the less competitive organisms are not eliminated, but stable coexistence can occur. Commensalism and mutualism among some of the organisms could be responsible for this, or it may result from a population that that preys on the competing organisms. The competing populations can be stabilized by feedback control. An interaction between organisms in which one benefits and one is harmed based on the ingestion of the smaller sized organism, the prey, by the larger organism, the predator. Predation is brought about by endocytosis and is restricted to certain protozoa and others with amoebal phases.