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Phase Variation in Xenorhabdus nematophilus
A Volgyi1, A Fodor, A Szentirmai
1Department of Biological Sciences, University of Wisconsin, Milwaukee, Wisconsin 53201, and Department of Genetics, Eotvos Lorand University, Budapest, and Department of Microbiology, Kossuth Lajos University, Debrecen, Hungary.
Applied and Environmental Microbiology
|December 14, 2005
Summary
Phase variation in Xenorhabdus nematophilus (X. nematophilus) shows that phase II cells exhibit variable virulence and motility. These traits depend on the bacterial strain and environmental conditions, impacting insect pathogenicity.
Area of Science:
- Microbiology
- Bacteriology
- Insect Pathology
Background:
- Xenorhabdus nematophilus is a symbiotic bacterium essential for entomopathogenic nematodes, exhibiting pathogenicity towards insects.
- Two cell types, phase I and phase II, exist in X. nematophilus, with phase II arising spontaneously under stationary conditions.
- Phase II cells typically lack products associated with phase I, suggesting altered functionality.
Purpose of the Study:
- To investigate phase variation in X. nematophilus by analyzing phenotypic traits of different strains.
- To define the variability in phase II cell characteristics, including virulence and motility.
Main Methods:
- Analysis of multiple X. nematophilus strains (19061, AN6, F1, N2-4) for phenotypic differences.
- Assessment of bacterial pathogenicity in Manduca sexta larvae.
- Evaluation of bacterial motility and outer membrane protein (OpnB) production under varying conditions.
Main Results:
- Phase II variants displayed variable virulence; AN6/II and N2-4 were less virulent or avirulent, while F1/II and 19061/II retained virulence.
- Motility varied among phase II cells; 19061/II was motile, and AN6/II regained motility in low osmolarity, whereas F1/II remained nonmotile.
- Phase II cells generally did not produce the stationary-phase induced outer membrane protein, OpnB.
Conclusions:
- Phase variation in X. nematophilus involves strain-specific alterations in phenotypic traits.
- Virulence and motility of phase II cells are not uniform and are influenced by environmental factors.
- Despite variations, both phase I and phase II cells support nematode growth and development.