The outer surface lipoprotein (osp) layer forms an interface between the internal and the external
environment of the Lyme disease spirochete, Borrelia burgdorferi. The homeostatic maintenance of the
osp layer effectuates adaptation of B. burgdorferi as it gets transmitted from the tick vector to a mammalian
host and vice-versa. However, the regulation of the outer surface lipoproteins (osps) is still a conundrum
for borrelia scientists. Part of this dissertation inquires about the homeostatic maintenance of the osp layer.
We found that the deletion of the dominantly expressed tick phase osp, OspA, induces expression of two
other osps. OspD, and BBJ41. Also, increased expression of OspC was seen in borrelia mutants lacking
OspA, OspD, and BBJ41. These results suggest constant osp layer maintenance, irrespective of the presence
or the absence of the dominant Osps, like OspA and OspC. Furthermore, our conclusive electron
microscopic study demonstrates that the overall density of the osp layer remains identical in wild type and
mutant B. burgdorferi, lacking either several osps or the dominantly expressed OspA.
OspA is abundantly expressed on the borrelial surface as it persists in an unfed tick. A blood meal causes
rapid downregulation of OspA as B.burgdorferi prepares to infect the mammalian host. The downregulation
of OspA is speculated to be regulated by an unknown repressor protein. The remaining part of this
dissertation pertains to the investigation of this unknown repressor protein for ospA. The borrelia oxidative
stress regulator protein, BosR, has been attributed with an indirect role in OspA downregulation. However,
due to its homolgy with a family of transcriptional repressors, BosR is more likely to cause direct repression
of OspA. Therefore, we investigated the direct interaction of BosR and the ospA regulatory region. The
DNA binding experiments demonstrated that borrelia oxidative stress regulator, BosR, binds directly to the
cisI and cisII regulatory regions of ospA promoter. Thus, conclusively, BosR acts as a repressor protein
which causes OspA downregulation in B. burgdorferi.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-11072014-161553 |
| Date | 18 November 2014 |
| Creators | Dadhwal, Poonam |
| Contributors | Liang, Fang Ting, Stout, Rhett, Elzer, Philip H., Macaluso, Kevin, Gleason, Evanna L |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-11072014-161553/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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