Dr P. Rosa is studying very interesting topics within Lyme
and pertaining to the plasmid situation she states facts that are a bit different than other studiesResearch in this laboratory focuses on the spirochete Borrelia burgdorferi, the cause of Lyme disease, the most common arthropod-borne disorder in the United States. B. burgdorferi is maintained in nature through an infectious cycle between wild mammals and ticks. Occasionally, infected ticks feed upon humans and transmit Lyme disease.
Although human infection is not relevant to the transmission cycle, it has medical significance as a multisystemic, potentially chronic illness. The tick vector and the mammalian host represent two very different environments, and there is good evidence for differential gene expression by borreliae in these locations.
part of her attempt to understand the infectivity:
Our broad objective is to use a molecular genetic approach to elucidate the mechanisms of adaptation and variation in B. burgdorferi and their roles in the infectious cycle. The specific aims of our research are as follows:
2.Understand the structure and function of plasmids in B. burgdorferi. A distinguishing feature of the B. burgdorferi genome is the presence of a linear chromosome and multiple linear and circular plasmids. The genomic sequence of B. burgdorferi identified 21 different plasmids, representing the largest known complement of plasmids of all bacteria and constituting one third of the spirochete's DNA. More than 90% of the plasmid-encoded genes are unique to B. burgdorferi, without homologs in any other organisms, suggesting they encode functions pertinent to the distinctive lifestyle of the spirochete. Consistent with this hypothesis is growing evidence that B. burgdorferi plasmids carry genes critical for survival in or transmission between the tick and mammal host.
Despite the apparent significance of B. burgdorferi plasmids to its life cycle, relatively little is known about the mechanisms of plasmid replication and partitioning, or the functions of the proteins they encode. We have begun a series of experiments to test our hypothesis that the multiplicity and unusual structure of the DNA molecules that form the B. burgdorferi genome are intrinsic to the ability of the spirochete to adapt to, persist in, and be transmitted between the alternating mouse/tick environments of the infectious cycle
so DO plasmids have higher priority relevance after all ??