Affiliation:
1. Discipline of Pathology, University of Tasmania, Hobart, Tasmania 7001, Australia
2. Division of Genomic Medicine, University of Sheffield Medical School, Sheffield, United Kingdom
Abstract
ABSTRACT
Swarming motility, a flagellum-dependent behavior that allows bacteria to move over solid surfaces, has been implicated in biofilm formation and bacterial virulence. In this study, light and electron microscopic analyses and genetic and functional investigations have shown that at least 50% of
Aeromonas
isolates from the species most commonly associated with diarrheal illness produce lateral flagella which mediate swarming motility.
Aeromonas
lateral flagella were optimally produced when bacteria were grown on solid medium for ≈8 h. Transmission and thin-section electron microscopy confirmed that these flagella do not possess a sheath structure. Southern analysis of
Aeromonas
reference strains and strains of mesophilic species (
n
= 84, varied sources and geographic regions) with a probe designed to detect lateral flagellin genes (
lafA1
and
lafA2
) showed there was no marked species association of
laf
distribution. Approximately 50% of these strains hybridized strongly with the probe, in good agreement with the expression studies. We established a reproducible swarming assay (0.5% Eiken agar in Difco broth, 30°C) for
Aeromonas
spp. The
laf
-positive strains exhibited vigorous swarming motility, whereas
laf
-negative strains grew but showed no movement from the inoculation site. Light and scanning electron microscopic investigations revealed that lateral flagella formed bacterium-bacterium linkages on the agar surface. Strains of an
Aeromonas caviae
isolate in which lateral flagellum expression was abrogated by specific mutations in flagellar genes did not swarm, proving conclusively that lateral flagella are required for the surface movement. Whether lateral flagella and swarming motility contribute to
Aeromonas
intestinal colonization and virulence remains to be determined.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
110 articles.
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