Micro-organisms are commonly patented, including new species or strains, which have often been genetically engineered to include a specific gene or genes required for a particular metabolic pathway. Within Europe, the term "micro-organism" extends to cover bacteria, yeast, fungi, algae, protozoa, plan cells, and generally unicellular organisms propagated and manipulated in the laboratory. The U.S. definition is broadly similar, however, the precise protection available may vary in each country. Additionally, under the Budapest Treaty, micro-organisims, require a sample to be deposited at one of a number of designated depositories in addition to their description. The U.S. (as well as the U.K.) is a signatory of the Budapest Treaty, which allows for a single deposit to be considered when applying for a patent for a micro-organism.