Genomic Characteristics
The genome of B. burgdorferi (B31 strain) was the third microbial genome ever to be sequenced, following the sequencing of both H. influenzae and M. genitalium in 1995, and its chromosome contains 910,725 base pairs and 853 genes. One of the most striking features of B. burgdorferi as compared with other bacteria is its unusual genome, which is far more complex than that of its spirochetal cousin Treponema pallidum, the agent of syphilis. In addition to a linear chromosome, the genome of B. burgdorferi strain B31 includes 21 plasmids (12 linear and 9 circular) – by far the largest number of plasmids found in any known bacterium. Genetic exchange, including plasmid transfers, contributes to the pathogenicity of the organism. Long-term culture of B. burgdorferi results in a loss of some plasmids and changes in expressed protein profiles. Associated with the loss of plasmids is a loss in the ability of the organism to infect laboratory animals, suggesting the plasmids encode key genes involved in virulence.
Chemical analysis of the external membrane of B. burgdorferi revealed the presence of 46% proteins, 51% lipids and 3% carbohydrates.
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