Abstract

The rhizobium – legume symbiosis is a complex process that involves genetic cooperation from both bacteria and plants. Previously, our lab described naturally occurring accessory plasmids in rhizobia that inhibit this cooperation. A transposon mutagenesis was performed on the plasmids to detect the genetic factor that blocked nitrogen fixation. Several of the plasmids were found to possess a replication operon that when disrupted by transposon insertion, restored symbiotic function. This study describes an in-depth investigation into one of those plasmids, pHRC377, and into its replication operon. The operon, which we have called repA2C2, comes from the repABC family of replication and partitioning systems commonly found in alphaproteobacteria. In this study we show that this operon is not necessary for pHRC377 replication in LB culture or free living cells, but is necessary for plasmid amplification in the plant, specifically during rhizobial differentiation into nitrogen fixing bacteroids. We also show how the other repABC type operons on pHRC377 function in relation to plasmid maintenance and copy number during endoreduplication and how they do not have the same phenotypic effect as repA2C2.

Degree

MS

College and Department

Life Sciences; Microbiology and Molecular Biology

Rights

http://lib.byu.edu/about/copyright/

Date Submitted

2015-12-01

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd8203

Keywords

Sinorhizobium meliloti, Medicago truncatula, repABC, symbiosis, nitrogen fixation

Included in

Microbiology Commons

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