Characterization of Genetic Differences between Mycobacterium avium subsp. paratuberculosis Type I and Type II Isolates

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Abstract
A combination of representational difference analysis and comparative DNA sequencing revealed that four type I (sheep) isolates of Mycobacterium avium subsp. paratuberculosis were differentiated from nine type II (bovine) isolates by the presence of an 11-bp insertion in a novel M. avium subsp. paratuberculosis -specific region of genomic DNA. Further, our studies show that M. avium subsp. paratuberculosis type I isolates contain three type-specific loci that are missing in M. avium subsp. paratuberculosis type II but are present in M. avium subsp. avium . Taken together, the results are consistent with the hypothesis that M. avium subsp. paratuberculosis type I strains are an evolutionary intermediate between M. avium subsp. avium and M. avium subsp. paratuberculosis type II isolates or share a subset of M. avium subsp. avium type-specific loci through horizontal transfer.