Investigative Labs
-
BIOL 315
The lab portion of the Microbiology course culminates in four-week-long
independent projects. The observation that Agrobacterium tumefaciens can transfer a variety
of DNA molecules, including IncQ plasmids, to plants raises the possibility that antibiotic
resistance genes present in environmental samples (e.g. manure used as fertilizer) could
find their way into crop plants. Inspired by the recent work from members of the European
consortium on Mobile Elements' Contribution to Bacterial Adaptability and Diversity, the
students designed their own experiments to study the prevalence and transfer of IncQ-related
and other plasmids in local environmental samples. They selected for copper- or
streptomycin-resistance in orchard soils, or for gentamycin-resistance in pig manure, either
by plating for resistant bacteria, or by mixing the soil community bacteria with a recipient
agrobacterium strain and recovering a mobilizable plasmid carrying the resistance marker.
Individual pairs of students then chose, for example, to investigate whether inter-species
transfer is as efficient as conjugation between cells of the same species; to test whether
multiple resistance traits were conferred by the same plasmid; and/or to determine the
incompatibility grouping of their resistance-conferring plasmids, using Inc-specific PCR
primers.