Transport and Catabolism of Inositol Derivatives in Sinorhizobium Meliloti


Mary Thwaites

Date of Award


Degree Name

Master of Science


Biological Sciences

First Advisor

Dr. Silvia Rossbach

Second Advisor

Dr. John Geiser

Third Advisor

Dr. Brian Tripp


Sinorhizobium, Meliloti, Inositol, metabolism, pinitol

Access Setting

Masters Thesis-Abstract Only

Restricted to Campus until



Sinorhizobium meliloti is the nitrogen-fixing symbiont of alfalfa. In this thesis two genetic loci in S. meliloti are investigated, one involved in transport of inositols, and the second needed for catabolism of methylated inositol derivatives. The first locus contains the ibpA-iatA-iatP operon encoding proteins of an ABC transporter. A mutant with an insertion in ibpA, which encodes the periplasmic-binding protein of the ABC transporter, showed a three-day growth delay as compared to the wild type when grown with inositol as sole carbon source. Complementation with the entire ibpA-iatA-iatP operon was necessary to restore wild-type-like growth. It was concluded that this operon encodes a major inositol transporter, but there may be a second inositol transporter present in S. meliloti. S. meliloti can also utilize a methylated inositol derivative, pinitol (3-O-methyl-D-chiro-inositol). Mutants with insertions in the mocD and mocE genes, which encode a hydrocarbon oxygenase and a ferredoxin, respectively, were able to use D-chiro-inositol but not pinitol as sole carbon source. It was concluded that the mocDE gene products play a role in pinitol catabolism, probably through the demethylation of pinitol.


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