(Science: molecular biology) refers to any number of methods to contain genetically engineered organisms by creating biochemical barriers to prevent them from growing outside the laboratory.
in the case of bacteria and yeasts, genes in the organisms may be altered so that they need to have a supply of a nutrient that is normally found only in the laboratory.
When some potentially dangerous experiments are undergone by scientists, the organisms involved may be genetically engineered or extremely toxic to other organisms in some way. In such examples, the experiment must be contained in order to preserve the external environment (i.e. the open air) from this dangerous entity.