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Journal of Bacteriology, May 1999, p. 3220-3225, Vol. 181, No. 10
Institute of Biological Sciences, National
Research Council Canada,1 and Electron
Microscopy Unit, Faculty of Medicine, University of
Ottawa,2 Ottawa, Ontario, Canada
Received 17 November 1998/Accepted 26 February 1999
The expression of nonagglutinating fimbriae (NAF) and
mannose-resistant/Proteus-like (MR/P) pili in swarming
colonies of Proteus mirabilis was investigated. Elongated
swarmer cells do not express pili, and the relative number of bacteria
expressing NAF during swarming and early consolidation phases was very
low (<5%). Relative expression of NAF in a terrace increased to
approximately 30% at 48 h. We also determined the expression of
NAF and MR/P pili in two phenotypically distinguishable regions of each
terrace. The expression of both NAF and MR/P pili was always higher in the region closer (proximal) to the middle of the colony than in the
distal region of the terrace. The relative numbers of bacteria expressing NAF or MR/P pili in the proximal region were between 39.1 and 63% and between 5.9 and 7.7%, respectively. In the distal region,
expression levels were between 20.8 and 27.3% and between 3.7 and
5.6%, respectively. A time course experiment testing NAF expression in
both the proximal and distal regions of a terrace indicated that NAF
expression in the proximal regions was always higher than in the distal
regions and increased to a plateau 40 to 50 h after the start of
the swarming phase for any given terrace. These results indicate that
expression of NAF or MR/P pili in swarming colonies of P. mirabilis is highly organized, spatially and temporally. The
significance of this controlled differentiation remains to be uncovered.
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Differential Expression of Nonagglutinating
Fimbriae and MR/P Pili in Swarming Colonies of Proteus
mirabilis
*
Corresponding author. Mailing address: 100 Sussex Dr.,
Rm. 3005, Ottawa, Ontario K1A 0R6, Canada. Phone: (613) 993-5900. Fax: (613) 952-9092. E-mail: luc.berube{at}nrc.ca.
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