Longum

Longum is the neuter form of the Latin adjective longus, meaning long. In biological nomenclature, longum is commonly used as a species epithet in the scientific names of organisms. The form of the epithet agrees with the gender of the genus: longus for masculine genera, longa for feminine, and longum for neuter.

One well-known example is Bifidobacterium longum, a Gram-positive, anaerobic bacterium that inhabits the human intestinal tract. It is widely studied as a probiotic, and several subspecies have been described, including Bifidobacterium longum subsp. infantis and Bifidobacterium longum subsp. longum.

In other taxa, longum appears in plant and animal names as a descriptive epithet; the meaning remains tied to the organism’s elongated form, and the exact implication varies with the genus.

The epithet derives from Latin and reflects the long-standing tradition of binomial nomenclature established by Carl Linnaeus; its use continues in contemporary taxonomy.