Affiliation:
1. Department of Genetics and Microbiology, University Medical Center,1 and
2. Laboratory of General Microbiology, Sciences III, University of Geneva,2 CH-1211 Geneva 4, Switzerland
Abstract
ABSTRACT
We describe swarming in
Pseudomonas aeruginosa
as a third mode of surface translocation in addition to the previously described swimming and twitching motilities. Swarming in
P. aeruginosa
is induced on semisolid surfaces (0.5 to 0.7% agar) under conditions of nitrogen limitation and in response to certain amino acids. Glutamate, aspartate, histidine, or proline, when provided as the sole source of nitrogen, induced swarming, while arginine, asparagine, and glutamine, among other amino acids, did not sustain swarming. Cells from the edge of the swarm were about twice as long as cells from the swarm center. In both instances, bacteria possessing two polar flagella were observed by light and electron microscopy. While a
fliC
mutant of
P. aeruginosa
displayed slightly diminished swarming, a
pilR
and a
pilA
mutant, both deficient in type IV pili, were unable to swarm. Furthermore, cells with mutations in the
las
cell-to-cell signaling system showed diminished swarming behavior, while
rhl
mutants were completely unable to swarm. Evidence is presented for rhamnolipids being the actual surfactant involved in swarming motility, which explains the involvement of the cell-to-cell signaling circuitry of
P. aeruginosa
in this type of surface motility.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
678 articles.
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