POSTERS - BLAST X - University of Utah

BLAST X Poster #72
A MECHANICAL AND GENETIC STUDY OF ESCHERICHIA COLI SWARMING MOTILITY
Matthew Copeland and Douglas B. Weibel
Department of Biochemistry, University of Wisconsin-Madison, WI 53706 USA
Bacterial swarming is a phenotype associated with the motility of bacteria across
surfaces in search of resources. In this abstract we describe two approaches to understand this
phenotype in Escherichia coli; a ‘mechanistic’ approach to elucidate potential flagella/flagella
interactions between adjacent swarming cells and a genetic investigation to chart the
expression of genes unique to the swarming phenotype.
In contrast to swimming motility, swarming bacteria cells migrate cooperatively across
surfaces. The role of physical interactions in the coordination of swarming motility is unknown. It
has been shown that swarming bacteria align along their long axis and move as multicellular
rafts from which the characteristic dynamic swirling patterns of swarming emerge. The
alignment of cells may facilitate or accompany the intercellular bundling of flagella between
adjacent cells and play a role in the characteristic, coordinated movement observed during
swarming motility. To test this hypothesis, we have created strains of E. coli with fluorescent
flagella and are using space- and time-resolved fluorescence resonance energy transfer (FRET)
to measure flagella/flagella interactions.
Iron starvation is known to signal swarmer cell differentiation in Vibrio parahaemolyticus
and the genes for iron uptake and metabolism have been shown to be elevated in swarming
populations of Salmonella typhimurium. We have found that iron metabolism and iron
acquisition genes are upregulated in swarming cells of E. coli versus planktonic cells. A specific
role for iron in E. coli swarming cells is unknown. Like V. parahaemolyticus, iron starvation may
be a signal for swarmer cell differentiation in E. coli or swarming development and motility may
require intracellular levels of iron in excess of those necessary for growth under vegetative
conditions. We are exploring the role of iron in E. coli swarming using a combination of chemical
and gene expression techniques and strains containing iron metabolism gene knockouts.
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