ABSTRACT: The family Corynebacteriaceae is composed of the type genus Corynebacterium with almost 90 species and the monospecific genus Turicella. The status of Turicella as a genus is supported by phenotypic characteristics. Bothtaxa form a distinct clade in the order Corynebacteriales which is clearly separated from the related families Dietziaceae and Tsukamurellaceae. Most Corynebacterium species contain mycolic acids with 22–36 carbons, though few species and Turicella otitidis lack this component. The peptidoglycan is of the A1γ type with directly cross-linked meso-diaminopimelic acid. Arabinose and galactose are the major cell-wall sugars. Fatty acid profiles are rich in saturated and unsaturated components and may contain tuberculostearic acid.   TABLE OF CONTENTS: 1.        Introduction 2.        Definition of Corynebacterium 3.        Taxonomy 4.        Genomics 5.        Characteristics 6.        Cell wall 7.        Culture 8.        Habitat 9.        Role in diseases 10.      Industrial uses 11.      Pathogenic pathway and metabolism 12.      Pathogenicity 13.      Antibiotics susceptibility and Mechanisms of resistance 14.      Ecology CHAPTER 1   Corynebacterium is a genus of Gram-positive bacteria and most are aerobic. They are bacilli (rod-shaped), and in some phases of life they are, more specifically, club-shaped, which inspired the genus name (coryneform means "club-shaped").It is a club bacterium, straight to slightly curved rods with tapered ends. Rods are usually short or of medium length. Club-shaped forms may be observed; sometimes ellipsoidal, ovoid or rarely, “whip handles” or thinner rods with bulges. Snapping division produces angular and palisade arrangements of cells. Gram-stain-positive; some cells stain unevenly. Metachromatic (synonym being polyphosphate) granules may be observed for some species. Not-acid-fast (Ziehl–Neelsen stain), and no species has aerial mycelium. All species are non-motile. All species are catalase positive. All species are oxidase negative except for Corynebacteriumbovis, Corynebacteriumaurimucosum, Corynebacteriumdoosanense, and Corynebacteriummaris. Many species of Corynebacterium are facultatively anaerobic and some are aerobic, Chemoorganotrophs. Some species are lipophilic. Many species produce acid from glucose and some other sugars in peptone media. Several species alkalinize citrate as sole carbon sources, but most do not. Corynebacteria are widely distributed in nature in the microbiota of animals (including the human microbiota) and are mostly innocuous, most commonly existing in commensal relationships with their hosts. Some, such as C. glutamicum, are commercially useful. Others can cause human disease, including, most notably, diphtheria, which is caused by C. diphtheriae. As with various species of amicrobiota (including their relatives in the genera Arcanobacterium and Trueperella), they usually are not pathogenic, but can occasionally opportunistically capitalize on atypical access to tissues (via wounds) or weakened host defenses.