The two motility systems of Myxococcus xanthus show different selective advantages on various surfaces.
Myxococcus xanthus, a bacterium that forms fruiting bodies, moves by gliding motility utilizing dual motility systems that differ both genetically and morphologically [system A, having at least 21 genetic loci and moving mainly single cells, and system S, having at least 10 genetic loci and moving groups (rafts) of cells] [Hodgkin, J. & Kaiser, D. (1979) Mol. Gen. Genet. 172, 177-191]. In this study, we found that A- and S-gliding-motility systems have different selective advantages on surfaces containing different concentrations of agar. We observed that colonies of A+S- cells (A-motile cells) swarmed better than A-S+ cells (S-motile cells) on relatively firm and dry surfaces (e.g., 1.5% agar). In contrast, colonies of A-S+ cells swarmed much better than A+S- cells on soft and wet surfaces (e.g., 0.3% agar). Individual A-motile cells moved at a rate of 2-4 microns/min on 1.5% agar but they barely moved on 0.3% agar (< 0.5 microns/min); in contrast S-motile cells moved 3-5 times faster on 0.3% agar than on 1.5% agar. Wild-type cells with both A- and S-motility systems were able to move well over a wide range of surfaces. These results suggest that dual motility systems enable the myxobacteria to adapt to a variety of physiological and ecological environments and show similarities in function to the dual motility systems of flagellated bacteria such as Vibrio spp.
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Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Zusman
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D000362:Agar / Q000494:pharmacology; D001431:Bacteriological Techniques; D002465:Cell Movement / Q000187:drug effects; D005838:Genotype; D016941:Myxococcus xanthus / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D010641:Phenotype; D013045:Species Specificity; D001616:beta-Galactosidase / Q000378:metabolism
D000362:Agar; D001616:beta-Galactosidase