Olivia Walser

Date of Defense


Date of Graduation



Biological Sciences

First Advisor

Silvia Rossbach

Second Advisor

Todd Barkman


Sinorhizobium meliloti is the bacterial endosymbiont which lives within the root nodules alfalfa (Medicago sativa). While S. meliloti provides its plant host nitrogen through nitrogen fixation, the plant provides nutrients for the bacteria. How S. meliloti metabolizes the plant-provided carbon sources scyllo-inositol and pinitol are the focus of the work described here. Previous work in our laboratory demonstrated that the iolY gene is essential for growth with scyllo-inositol and that the mocDEF-smb20821 genes play a role in pinitol utilization. A complementation experiment was used to verify that the iolY- phenotype is due to the insertion in the iolY gene and not due to a second site mutation elsewhere in the genome. A survey of the distribution of the pinitol catabolism genes among the genomes of Sinorhizobium, most of which have been recently sequenced, was performed and revealed that S. meliloti USDA1021a does not possess the pinitol catabolism genes. When tested for the ability to grow with pinitol as sole carbon-source, the USDA1021a strain was not able to grow - further suggesting that mocDEF-smb20821 are indeed responsible for pinitol catabolism. Also described is the use of S. meliloti USDA1021a as a genomic tool with which we hope will be useful in further delimiting the pinitol catabolism genes. This work has elucidated some remaining questions produced by previous work in our laboratory concerning inositol derivatives while also describing methods with which scyllo-inositol and pintol catabolism can be further investigated.

Access Setting

Honors Thesis-Restricted