Mycoplasma gallisepticum

• Domain: Bacteria
•     Phylum: Firmicutes
•         Class: Mollicutes
•             Order: Mycoplasmatales
•                 Family: Mycoplasmataceae
•                     Genus: Mycoplasma
•                         Species: Mycoplasma gallisepticum

Mycoplasma gallisepticum is a small cell wall-less bacterium that belongs to the class Mollicutes. It has a very small genome of 996,422 bp for the R_low strain with an overall G+C content of 31 mol%. It contains 742 putative coding DNA sequences (CDSs), representing a 91% coding density (Papazisi et al., 2003). This small genome accounts for its complex nutritional requirements and its obligate parasitic mode of life with a high degree of dependence on the host animal. Mg has a flasked shaped appearance with a differentiated tip structure also known as an attachment organelle which binds to sialoglycoproteins (Glasgow and Hill, 1980). The organism has a gliding motility and always glides in the direction of the tip structure. Indikova et al. (2014) determined that cytadherence proteins GapA and CrmA are required for gliding. Loss of GapA and CrmA resulted in the loss of motility and led to a drastic change in the flask-shape of the cells. The organism has mechanisms which can be used for survival or to evade the host immune response or antibiotic treatment, this includes variable surface proteins VlhA (Browning et al., 2010) and the ability to form biofilms (Chen et al., 2013).

With the lack of a cell wall these highly pleomorphic organisms are not usually detected by standard light microscopy of gram stained cultures. Growth on suitable mycoplasma media results in typical “fried egg” like colonial morphology.

Mg has been shown to survive for up to 3 days in chicken droppings at 20°C or in egg yolk for up to six weeks at 20°C. It has been shown to be viable after two days on straw, cotton and rubber.