Mycoplasmas are members of the class Moliicutes which are the smallest self-replicating organisms yet to be described. They have very small genomes and it appears that over time they have used the process of reductive evolution to rid themselves of non-essential genes. For instance, they lack a cell wall, and can't synthesize any amino acids. This makes them obligate parasites as they must obtain most of their building blocks from their host. Mycoplasmas may be thought of as simple organisms, but this is not at all accurate. They are very complex and in some ways quite advanced organisms. They have devised mechanisms that allow them to be found in nearly every niche in nature. Moliicutes are found in mammals, reptiles, fish, arthropods, insects andplants and it is likely we have only discovered a small portion of the total number of species that actually exist. Mycoplasmas tend to reside on mucosal surfaces and cause respiratory and urogentital infections. Additionally, in 2001 the genus Haemobartonella was reclassified to the genus Mycoplasma and these organisms are known as 'haemoplas-mas'. These haemoplasmas infect red blood cells and are a cause of hemolytic anemia.
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