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Colonial and Cellular Polymorphism in Xenorhabdus luminescens
R E Hurlbert1, J Xu, C L Small
1Department of Microbiology, Washington State University, Pullman, Washington 99164-4340.
Applied and Environmental Microbiology
|May 1, 1989
Summary
Xenorhabdus luminescens exhibits high phenotypic plasticity, with primary and secondary forms generating diverse colony variants. These variants, including small-colony (SC) forms, show high-frequency switching and reversion, indicating genetic instability.
Area of Science:
- Microbiology
- Bacteriology
- Genetics
Background:
- Xenorhabdus luminescens is a bacterial symbiont of entomopathogenic nematodes.
- This species is known for its phenotypic diversity and ability to switch between different forms.
Purpose of the Study:
- To investigate the high degree of polymorphism in a Xenorhabdus luminescens strain.
- To characterize the different colony forms and their interconversion capabilities.
Main Methods:
- Isolation and characterization of primary, secondary, and variant colony forms of Xenorhabdus luminescens.
- Analysis of colony morphology, pigmentation, luminescence, antimicrobial production, and cellular protein composition.
- DNA fingerprinting to assess genetic relatedness.
- Assessment of colony variant frequencies and reversion rates.
Main Results:
- A highly polymorphic Xenorhabdus luminescens strain was isolated, with distinct primary (luminescent, nonswarming, yellow pigment, antimicrobial production) and secondary (weakly luminescent, orange pigment, no antimicrobial production) forms.
- Both primary and secondary forms generated various colony variants, including nonswarming, swarming, and small-colony (SC) forms, at frequencies exceeding spontaneous mutation rates.
- SC forms exhibited distinct morphology and protein composition, reverted frequently to parental types, and showed age-dependent parental cell proportions.
- While the primary-to-secondary switch was stable, other colony forms demonstrated high-frequency switching between phenotypes.
Conclusions:
- Xenorhabdus luminescens displays remarkable phenotypic plasticity, generating multiple colony variants through high-frequency switching.
- The observed instability and high reversion rates of variant forms, particularly SC forms, suggest complex regulatory mechanisms governing bacterial development and adaptation.
- Understanding this polymorphism is crucial for comprehending the ecological role and evolutionary dynamics of Xenorhabdus luminescens.
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