hygroscopicus

Hygroscopicus is a Latin adjectival form used as a species epithet in the scientific names of several organisms. As a nomenclatural element, it is typically capitalized as part of the binomial name in zoological and botanical nomenclature, but is not a taxon itself; rather, it describes a characteristic or is a traditional label.

The most prominent use is Streptomyces hygroscopicus, a soil-dwelling actinobacterium in the genus Streptomyces. Members of this group are noted for producing a variety of bioactive compounds. Streptomyces hygroscopicus is best known for producing rapamycin (sirolimus), an immunosuppressant drug that inhibits the mechanistic target of rapamycin (mTOR) pathway and has applications in organ transplantation and cancer therapy, as well as research into aging and metabolism.

The epithet hygroscopicus occurs in other species names as well, across bacteria, fungi, and plants, but such occurrences are relatively uncommon and the same epithet does not imply close relatedness among the organisms bearing it. The term itself derives from Latin hygroscopicus, meaning “hygroscopic” or moisture-absorbing, reflecting a trait thought to be associated with the organism or its habitat in some historical context. In taxonomy, epithets are descriptive or commemorative and do not by themselves indicate taxonomic rank beyond the species level.

See also: rapamycin, sirolimus, Streptomyces.