Brugia Malayi - Clark Science Center - Smith College

Generating Images of Swarming Motility Across Strains of Escherichia coli
Shannon Pettit
Swarm motility assays conducted as part of my honors project revealed differences in the swarming motility of E. coli across
different strains, temperatures, and types of growth media. These analyses of motility provide a phenotypic comparison for gene
expression data generated in the White-Ziegler laboratory. Recent microarray data from our lab has shown that genes involved in
flagellar motility are down-regulated in a 37˚C to 23˚C transition for the non-pathogenic K-12 strain MG1655, while qRT-PCR data
indicates that those same genes show increased expression after a 23˚C to 37˚C upshift. These gene expression patterns are not
conserved across strains, where uropathogenic strain CFT073 demonstrates decreased motility gene expression after a 23˚C to 37˚C
temperature shift.
To generate images that support the phenotypic motility data, reduced-agar swarm motility plates were prepared and inoculated
with the three strains of interest and a negative control. Images were taken of these plates at specific times after inoculation. These
images were taken with illumination from below with indirect white light in a covered environment to minimize glare.
These images support our previous findings that there are differences in motility based on strain and environmental conditions
that include ambient temperature and the nutrient richness of the growth media. Uropathogenic strain CFT073 was motile in
all media and temperature conditions, while enteropathogenic strain E2348/69 and K-12 strain MG1655 are more sensitive to
environmental conditions. These two strains show high levels of motility on nutrient rich media, but minimal or no motility on a
nutrient poor medium (Figure 1).
The importance of these images is how they support the previously generated swarm motility data described in my honors
project, which I presented in poster form at the American Society of Microbiology 2012 Annual Meeting in San Francisco, CA.
They will be used in a publication alongside the data to further describe the effects of ambient temperature shifts on the gene
expression and morphology of E. coli. (Supported by the Blakeslee Fund in the Biological Sciences)
Advisor: Christine White-Ziegler
2012
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