Coryneform ​Bacteria
By M Borisova, H Coates, K Durber-Stoneman, E Wilcher
Corynebacterium
Corynebacterium are a group of micro-organisms that are widely distributed throughtout nature and can be present in high numbers. Usually Corynebacterium are innocuous, they do not cause harm, however some species are highly pathogenic; i.e. Corynebacterium diphtheriae. Corynebacterium are capable of causing disease in other animals, not just humans, and also disease in plants (Chiller et al., 2001). This can also harm us as it can lead to economic difficulty. On the other hand non-pathogenic species of Corynebacterium are thought to be beneficial to economy. This is because they have important applications in industrial production of amino acids, nucleotides and other nutritional factors. In addition they are involved in the microbial conversion of steroids and the ripening of particular cheeses. Coryneforms are a group of micro-organisms that have similar characteristics to Corynebacterium, however Corynebacterium do tend to have one key difference to the rest of the coryneform bacteria. This is that Corynebacterium tend to have metachromic granules present within their cell cytoplasm whereas other groups of bacteria categorised as coryneforms do not have these granules present in their cytoplasm (Madigan et al., 2012).
Habitat
Corynebacterium have a number of different habitats, ranging from soil, activated sludge and plant surfaces to the sea and on fish. These bacteria are also present in food products, especially dairy, and have also been isolated from poultry deep litter. Not only are Corynebacterium diverse and adapted to a range of different habitats, but they are adapted enough to live symbiotically in the commensal microflora of man and animals. Corynebacterium that are considered part of the commensal microflora are usually known as diphtheroids (Dworkin et al., 2006).
Pathogenicity
Corynbacterium tend to be diphtheroids meaning they are non-diphtheral and are usually innocuous. Some species of Corynebacterium are opportunistic pathogens and so will only cause disease when an opportunity arises. For example when a person is immunocompromised the organism may choose to become pathogenic and infect host tissues (Dworkin et al., 2006). Some examples of pathogenic Corynebacterium includes: C. jeikeium, C. striatum and C. urealyticum. These examples show resistance to a range of antibiotics, however they can currently be treated using vancomycin (Pitcher et al., 1992). Corynebacterium when present in plants can cause two types of disease: vascular and hypertrophic. Examples of each respectively are Corynebacterium flaccumfaciens and Corynebacterium fascians. The latter is a common causer of leafy gall disease (Lelliott, 1966).
Characteristics
Corynbacterium are Gram-positive, aerobic, non-motile and pleomorphic rod-shapes. These rods are often formed irregularly and can take on: club-shapes, V-shapes or generally irregular. V-shaped cells are the result of snapping division. Studies have suggested that coryneform bacteria were distinguished from true bacteria on the basis of their mode of snapping division rather than the use of cell division (Madigan et al., 2012). The coryneforms themselves were divided into five groups in relation to their principle amino acid in their cell wall: 2,4- diaminobutyric acid (DAB), DL- and LL- diaminopimelic acid, lysine and ornithine. Corynebacterium tend to exhibit either DL-diaminopimelic acid or ornithine in their cell wall (Chapot-Chartier and Kulakauskas, 2014).
