Structural peculiarities of linear megaplasmid,pLMA1, from Micrococcus luteus interfere with pyrosequencing reads assembly

Different strains of Micrococcus luteus, isolated from high-altitude Argentinean wetlands, were recently reported to harbour the linear plasmids pLMA1, pLMH5 and pLMV7, all of which with 5′-covalently attached terminal proteins. The link between pLMA1 and the host’s erythromycin resistance as well as further presumptive qualities prompted us to perform a detailed characterization. When the 454 technology was applied for direct sequencing of gel-purified pLMA1, assembly of the reads was impossible. However, combined Sanger/454 sequencing of cloned pLMA1 fragments, covering altogether 23 kb of the 110-kb spanning plasmid, allowed numerous sequence repeats of varying in lengths to be identified thus rendering an explanation for the above 454 assembly failure. A large number of putative transposase genes were identified as well. Furthermore, a region with five putative iteron sequences is possibly involved in pLMA1 replication.