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Spatial control of the GTPase MglA by localized RomR–RomX GEF and MglB GAP activities enables Myxococcus xanthus motility


The rod-shaped Myxococcus xanthus cells move with defined front–rear polarity using polarized motility systems. A polarity module consisting of the small GTPase MglA, its cognate GTPase activating protein (GAP) MglB and RomR establishes this polarity. Agl–Glt gliding motility complexes assemble and disassemble at the leading and lagging pole, respectively. These processes are stimulated by MglA-GTP at the leading and MglB at the lagging pole. Here, we identify RomX as an integral component of the polarity module. RomX and RomR form a complex that has MglA guanine nucleotide exchange factor (GEF) activity and also binds MglA-GTP. In vivo RomR recruits RomX to the leading pole forming the RomR–RomX complex that stimulates MglA-GTP formation and binding, resulting in a high local concentration of MglA-GTP. The spatially separated and opposing activities of the RomR–RomX GEF at the leading and the MglB GAP at the lagging cell pole establish front–rear polarity by allowing the spatially separated assembly and disassembly of Agl–Glt motility complexes. Our findings uncover a regulatory system for bacterial cell polarity that incorporates a nucleotide exchange factor as well as an NTPase activating protein for regulation of a nucleotide-dependent molecular switch and demonstrate a spatial organization that is conserved in eukaryotes.

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Fig. 1: RomX is important for reversals in the T4P-dependent motility system and essential for gliding motility.
Fig. 2: RomX acts in the same pathway as MglA, MglB and RomR.
Fig. 3: RomX is polarly localized.
Fig. 4: RomR–RomX complex interacts with MglA-GTP and has GEF activity.
Fig. 5: RomR and RomX are important for Agl–Glt complex formation and are incorporated into these complexes.
Fig. 6: Model for front–rear polarity in M. xanthus.

Data availability

The authors declare that all data supporting this study are available within the article and its Supplementary Information files or are available from the corresponding author on request.

Code availability

The MATLAB script used in this study is available from the corresponding author upon request.


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The authors thank D. Skotnicka for construction of SA8802 as well as A. Treuner-Lange and T. Bender for construction of pMAT162 and pTB005, respectively. This work was funded by the Deutsche Forschungsgemeinschaft (project no. 269423233) within the framework of the Transregio 174 ‘Spatiotemporal dynamics of bacterial cells’ (to U.G. and L.S.-A.) and the German–Israeli Project Cooperation ‘Spatial and Temporal Regulation of Macromolecular Complex Formation in Bacteria’ (to L.S.-A.), as well as by the Max Planck Society.

Author information




K.W., D.K., D.S. and L.S.-A. conceptualized the study. K.W., D.K., D.S., A.H., L.A.M.C. and A.P. conducted the experimental work. D.S., L.A.M.C., M.W., U.G. and L.S.-A. developed the methodology for quantification of microscopy images. D.S., A.H. and L.S.-A. analysed experimental data. D.S. and L.S.-A. wrote the original draft of the manuscript. D.S., L.S.-A., K.W., D.K., L.A.M.C., M.W., A.P. and U.G. reviewed and edited the manuscript. U.G. and L.S.-A. acquired funding. U.G. and L.S.-A. provided supervision.

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Correspondence to Lotte Søgaard-Andersen.

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Supplementary Notes, Supplementary Figures 1–10, Supplementary Tables 1–4 and Supplementary References.

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Supplementary Dataset

Original data for Figure 1e,f,h; Figure 2b,c; Figure 4d–f; and Supplementary Figure 5a,b.

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Szadkowski, D., Harms, A., Carreira, L.A.M. et al. Spatial control of the GTPase MglA by localized RomR–RomX GEF and MglB GAP activities enables Myxococcus xanthus motility. Nat Microbiol 4, 1344–1355 (2019).

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