Isolation and Characterization of a Burkholderia tuberum Exopolysaccharide Mutant
Mentor:Michelle Lum, Assistant Professor of Biology, Loyola Marymount University
Burkholderia tuberum is a beta-proteobacterium that engages in symbiotic relationships with legume plants, such as Phaseolus vulgaris (black bean), through nodulation. Nodules are special root structures that allow for bacterial fixation of atmospheric nitrogen. We are interested in identifying and characterizing Burkholderia tuberum mutants so that we can better understand the mechanisms by which this bacterium interacts with plants. The first step to generate mutants was to introduce the transposon vector, pRL27, from Escherichia coli into B. tuberum by conjugation. B. tuberum transposon mutants were selected using media with rifampsin, which selects for B. tuberum, and kanamycin, which selects for the presence of the transposon. Two hundred transposon –tagged mutants were then screened for alterations in motility and exopolysaccharide production, both processes implicated in bacterial-host interactions. When compared to the wild type, exopolysaccharide mutant SS6 absorbed the dyes and was extremely dry on yeast mannitol agar containing congo red and coomassie brilliant blue dyes, in comparison to wild type, which has a mucoidy appearance. Molecular methods were used to determine that the gene mutated encodes an S-adenosylmethionine-dependant methyltransferase. This indicates that methylation is involved in the regulation of exopolysaccharide production in B. tuberum.