Publication Year



Chemistry, mutants, rhizobium meliloti, cellobiose, glucose, enzyme assay


Chemistry | Physical Sciences and Mathematics


A transposon mutagenesis technique was used to generate large numbers of Rhizobium meliloti mutants. Mutants that were unable to grow on cellobiose were chosen as possible β-glucosidase underproducers. Of the nineteen mutants that were unable to grow on cellobiose, three were likely cellobiose-mutants (Km106, Km116, Km155).

An attempt was made to determine whether Km106, Km116, and Km155 are true β-glucosidase underproducers. The growth of these three mutants was compared to the growth of a known β-glucosidase underproducer (Rm131) and to the wild-type bacteria (Rm1021). These growth studies indicated that while the three mutants are comparable in growth rate to Rm131 and Rm1021 on lactose, they show slower growth compared to Rm1021 on cellobiose. This supports the idea that the three mutants are β-glucosidase underproducers.

To verify this, enzyme assays were conducted with the cellobiose analog, p-nitrophenyl-β-D-glucopyranoside. These assays confirmed that Rm131 is a β-glucosidase underproducer. The assays, however, indicated that the three mutants and Rm1021 cleave p-nitrophenyl-β-D-glucopyranoside equally well, whether the cells were grown on cellobiose or lactose. This suggests that the slower growth rate of the mutants on cellobiose (as shown in the growth studies) is not due to an underproduction of β-glucosidase.

Department 1 Awarding Honors Status