Project name: Mycoplasma mycoides

Description: Mycoplasma. This genus belongs to the class Mollicutes (phylum Tenericutes), a taxonomic group of small (0.3-0.8 micron diameter) monoderm bacteria characterized by the lack of cell walls, reduced genome sizes, and obligate parasitic lifestyles (Krieg et al., 2010). Over 120 obligate parasitic species found in a wide spectrum of hosts, including humans, animals, insects and plants. Human and animal mycoplasmas primarily inhabit mucous membranes of the respiratory and urogenital tracts, eyes, mammary glands and the joints. Infection typically proceeds through the attachment of bacteria to host cells via assorted adhesins or, in some species, through highly specialized surface protein appendages. In some cases, subsequent invasion of host cells results in a prolonged intracellular persistence that may cause lethality. The mycoplasmal cell membrane is rich in proteins that include extensive sets of prokaryotic lipoproteins, some of which contribute to surface diversity through mutation-prone contingency loci that mediate both phase-variable expression and structural variation. These adaptive strategies are involved in host cell attachment and invasion, as well as immune evasion. Most mycoplasmas are non-motile, with the exception of some flask-shaped human and animal pathogens (M. pneumoniae, M. genitalium, M. gallisepticum, M. pulmonis and M. mobile). Motile mycoplasmas glide on surfaces by mechanisms different from those of other microbes, employing cytoskeletal components that interact with unique motility proteins. Although mycoplasmas are dependent on their association with eukaryotic host tissue in nature, most can be cultivated axenically if their fastidious growth requirements are met. Nearly all mycoplasmas derive energy only from glycolytic pathways, whereas some can hydrolyze arginine. Cell division may proceed through normal binary fission, or through elongation of a parental cell to form multinucleated filaments that septate and subsequently break up to form coccoid bodies. Mycoplasma mycoides. Assigned to the genus Mycoplasma by historic taxonomic precedent, organism in the Mycoplasma mycoides phylogenetic cluster are in fact more closely related to other genera in the Mollicutes (Krieg et al., 2010). The group has recently been defined and divided by assorted taxonomic criteria (Krieg et al., 2010; Manso-Silvan et al., 2009) that place five taxa into three subclusters: (i)Mycoplasma mycoides, divided further into subspecies mycoides and subspecies capri (ii)Mycoplasma capricolum, divided further into subspecies capricolum and subspecies capripneumoniae and (iii)Mycoplasma leachii. These taxa form a tight phylogenetic clade, at the limit of resolution based on rRNA sequence similarity. All taxa of the group infect ruminant animals, in which they display a wide range of disease manifestations and severity. Specific subspecies cause two widespread and economically damaging diseases, contagious bovine pleuropneumonia (CBPP) in cattle and contagious caprine pleuropneumonia (CCPP) in goats, both of which are controlled under the Terrestrial Animal Health Code of the Office International des Epizooties. Subspecies of the cluster show overlaps in phenotypic traits, and incongruent phylogenetic branching based on different gene sets. Phase variable expression of surface antigens by reversible indel mutation is also known to occur in subspecies mycoides and capricolum (Persson et al., 2002; Wise et al., 2006). Consequently they continue to challenge the definition of species, and their selective detection and classification has required multiple approaches.

Last updated: 2007-04-06