Identification of a Burkholderia tuberum Nodulation Mutant
Mentor:Michelle Lum, Associate Professor of Biology, Loyola Marymount University
Identification of a Burkholderia tuberum Nodulation Mutant Nitrogen fixation is a plant process in which nitrogen (N₂) in the atmosphere is broken down into a usable form, ammonia (NH₃). Symbiotic, nitrogen-fixing bacteria that reside in structures on plant roots called nodules can be categorized as either α-rhizobia or β-rhizobia, with β-rhizobia being the more recent discovery. These bacteria provide fixed nitrogen to the plant in exchange for carbohydrates. Burkholderia tuberum is a β-rhizobium strain that is known to nodulate legumes such as beans and cowpea. The objective of this experiment is to identify a mutant that does not cause nodulation in plants in order to be able to identify genes important for symbiosis. To begin, a transposon mutagenesis was performed on B. tuberum and transposon mutants were identified. Pure cultures were obtained from the colonies. Phaseolus vulgaris (bean) seeds were germinated and using a hydroponic system, the plants were grown and tested for nodulation. During these trials, 84 different mutants were tested and compared to nodulated plants that had been inoculated with wild type B. tuberum. Plants inoculated with mutant ML30 showed no signs of nodulation, which was confirmed in three independent trials. Further molecular work is being conducted on ML30 in order to identify the mutated gene.