Recent Brandeis Ph.D graduate, Tracey Seier (Molecular and Cell Biology Program), Professor Sue Lovett, Research Assistant Vincent Sutera, together with former Brandeis undergraduates Noor Toha, Dana Padgett and Gal Zilberberg have developed a set of bacterial strains that can be used as “mutational reporters”.  Students in the Fall 2009 BIOL155a, Project Laboratory in Genetics and Genomics, course also assisted in the development of this resource. This work has recently been published in the journal Genetics.

These Escherichia coli strains carry mutations in the lacZ (β-galactosidase) gene that regain the ability to metabolize lactose by one, and only one, specific type of mutation. This set allows environmental compounds to be screened for effects on a broad set of potential mutations, establishing mutagen status and the mutational specificity in one easy step.

This strain set is improved over previous ones in the inclusion of reporters that are specific for certain types of mutations associated with mutational hotspots in gene. Mutations at these sites occur much more frequently than average and involve DNA strand misalignments at repeated DNA sequences rather than DNA polymerase errors. Such mutations are associated with human diseases, including cancer progression, and have been under-investigated because of the lack of specific assays. Using this strain set, Seier et al. also identified a mutagen, hydroxyurea, used in the treatment of leukemia and sickle cell disease, which affects only the “hotspot” class of mutations. This strain set, which will be deposited in the E. coli Genetic Stock Center,  will facilitate the screening of potential mutagens, environmental conditions or genetic loci for effects on a wide spectrum of mutational events.

Left: E. coli colonies showing lacZ mutant revertants (blue pimples) arising on a white colony on growth medium containing the beta-galactosidase indicator dye,  X-gal