Like various species of microbiota (including their relatives in the genera Arcanobacterium and Trueperella), they are usually not pathogenic, but can occasionally capitalize opportunistically on atypical access to tissues (via wounds) or weakened host defenses.

The genus Corynebacterium was created by Lehmann and Neumann in 1896 as a taxonomic group to contain the bacterial rods responsible for causing diphtheria.

Based on studies of 16S rRNA, they have been grouped into the subdivision of Gram-positive Eubacteria with high G:C content, with close phylogenetic relationships to Arthrobacter, Mycobacterium, Nocardia, and Streptomyces.

[8] The term comes from Greek κορύνη, korýnē 'club, mace, staff, knobby plant bud or shoot'[9] and βακτήριον, baktḗrion 'little rod'.

[11][12] Comparative analysis of corynebacterial genomes has led to the identification of several conserved signature indels (CSIs) that are unique to the genus.

Another cluster has been proposed, consisting of C. jeikeium and C. urealyticum, which is supported by the presence of 19 distinct conserved signature proteins which are unique to these two species.

They are pleomorphic through their lifecycles, they occur in various lengths, and they frequently have thickenings at either end, depending on the surrounding conditions.

lipophilum, C. bovis,[18] C. jeikeium, C. macginleyi, C. uropygiale,[19] and C. urealyticum), but medically relevant corynebacteria are typically not.

[20] The nonlipophilic bacteria may be classified as fermentative (such as C. amycolatum; C. argentoratense, members of the C. diphtheriae group, C. glucuronolyticum, C. glutamicum, C. matruchotii, C. minutissimum, C. striatum, and C. xerosis) or nonfermentative (such as C. afermentans subsp.

They form small, grayish colonies with a granular appearance, mostly translucent, but with opaque centers, convex, with continuous borders.

[citation needed] Corynebacterium species occur commonly in nature in soil, water, plants, and food products.

It is more common in developing countries[33] It can occasionally infect wounds, the vulva, the conjunctiva, and the middle ear.

[46] L-Lysine production is specific to C. glutamicum in which core metabolic enzymes are manipulated through genetic engineering to drive metabolic flux towards the production of NADPH from the pentose phosphate pathway, and L-4-aspartyl phosphate, the commitment step to the synthesis of L-lysine, lysC, dapA, dapC, and dapF.

These enzymes are up-regulated in industry through genetic engineering to ensure adequate amounts of lysine precursors are produced to increase metabolic flux.

Many genetic manipulations conducted in industry are by traditional cross-over methods or inhibition of transcriptional activators.

[49] Unlike gram-negative bacteria, the gram-positive Corynebacterium species lack lipopolysaccharides that function as antigenic endotoxins in humans.