<P> The term comes from the Greek κορωνη, corönë ("knotted rod") and βακτηριον, bacterion ("rod"). The term "diphtheroids" is used to represent corynebacteria that are non pathogenic; for example, C. diphtheriae would be excluded . The term diphtheroid comes from Greek διφθερα, diphthera--prepared hide, leather . </P> <P> Comparative analysis of corynebacterial genomes has led to the identification of several conserved signature indels which are unique to the genus . Two examples of these conserved signature indels are a two - amino - acid insertion in a conserved region of the enzyme phosphoribose diphosphate: decaprenyl - phosphate phosphoribosyltransferase and a three - amino - acid insertion in acetate kinase, both of which are found only in Corynebacterium species . Both of these indels serve as molecular markers for species of the genus Corynebacterium . Additionally, 16 conserved signature proteins, which are uniquely found in Corynebacterium species, have been identified . Three of the conserved signature proteins have homologs found in the Dietzia genus, which is believed to be the closest related genus to Corynebacterium . In phylogenetic trees based on concatenated protein sequences or 16S rRNA, the genus Corynebacterium forms a distinct clade, within which is a distinct subclade, cluster I . The cluster is made up of the species C. diptheriae, C. pseudotuberculosis, C. ulcerans, C. aurimucosum, C. glutamicum, and C. efficiens . This cluster is distinguished by several conserved signature indels, such as a two - amino - acid insertion in LepA and a seven - or eight - amino - acid insertions in RpoC . Also, 21 conserved signature proteins are found only in members of cluster I. 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 . Corynebateria have a high G + C content ranging from 46 - 74 mol% . </P> <P> The principal features of the Corynebacterium genus were described by Collins and Cummins in 1986 . They are gram - positive, catalase - positive, non spore - forming, non motile, rod - shaped bacteria that are straight or slightly curved . Metachromatic granules are usually present representing stored phosphate regions . Their size falls between 2 and 6 μms in length and 0.5 μm in diameter . The bacteria group together in a characteristic way, which has been described as the form of a "V", "palisades", or "Chinese letters". They may also appear elliptical . They are aerobic or facultatively anaerobic, chemoorganotrophs . They are pleomorphic through their lifecycles, they occur in various lengths, and they frequently have thickenings at either end, depending on the surrounding conditions . </P> <P> The cell wall is distinctive, with a predominance of meso diaminopimelic acid in the murein wall and many repetitions of arabinogalactan, as well as corynemycolic acid (a mycolic acid with 22 to 26 carbon atoms), bound by disaccharide bonds called L - Rhap - (1 → 4)--D - GlcNAc - phosphate . These form a complex commonly seen in Corynebacterium species: the mycolyl - AG--peptidoglican (mAGP). </P>

Bacteria can be arranged in a chinese letter pattern known as
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