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Appl. Environ. Microbiol., Apr 1995, 1408-1413, Vol 61, No. 4
A Givaudan, S Baghdiguian, A Lanois and N Boemare
Xenorhabdus spp., entomopathogenic bacteria symbiotically associated with
nematodes of the family Steinernematidae, occur spontaneously in two
phases. Phase I, the variant naturally isolated from the infective-stage
nematode, provides better conditions than the phase II variant for nematode
reproduction. This study has shown that Xenorhabdus phase I variants
displayed a swarming motility when they were grown on a suitable solid
medium (0.6 to 1.2% agar). Whereas most of the phase I variants from
different Xenorhabdus spp. were able to undergo cycle of rapid and
coordinately population migration over the surface, phase II variants were
unable to swarm and even to swim in semisolid agar, particularly in X.
nematophilus. Optical and electron microscopic observations showed
nonmotile cells with phase II variants of X. nematophilus F1 which lost
their flagella. Flagellar filaments from strain F1 phase I variants were
purified, and the molecular mass of the flagellar structural subunit was
estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to
be 36.5 kDa. Flagellin from cellular extracts or culture medium of phase II
was undetectable with antiserum against the denatured flagellin by
immunoblotting analysis. This suggests that the lack of flagella in phase
II cells is due to a defect during flagellin synthesis. The importance of
such a difference of motility between both phases is discussed in regard to
adaptation of these bacteria to the insect prey and the nematode host.
Copyright © 1995, American Society for Microbiology
Swarming and Swimming Changes Concomitant with Phase Variation in Xenorhabdus nematophilus
Pathologie Comparee, Universite Montpellier II, Institut National de la Recherche Agronomique--Centre National de la Recherche Scientifique (URA 1184), CP101, 34095 Montpellier Cedex 05, France
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