This Article Full Text Full Text (PDF) Other Versions of this Article: JB.00728-06v1 188/23/8196    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by O'Shea, T. M. Articles by Visick, K. L. Search for Related Content PubMed PubMed Citation Articles by O'Shea, T. M. Articles by Visick, K. L.

Diguanylate Cyclases Control Magnesium-Dependent Motility of Vibrio fischeri

Department of Microbiology and Immunology, Loyola University Chicago, 2160 S. First Ave., Bldg. 105, Maywood, Illinois 60153

Received 21 May 2006/ Accepted 5 September 2006

Flagellar biogenesis and hence motility of Vibrio fischeri depends upon the presence of magnesium. In the absence of magnesium, cells contain few or no flagella and are poorly motile or nonmotile. To dissect the mechanism by which this regulation occurs, we screened transposon insertion mutants for those that could migrate through soft agar medium lacking added magnesium. We identified mutants with insertions in two distinct genes, VF0989 and VFA0959, which we termed mifA and mifB, respectively, for magnesium-dependent induction of flagellation. Each gene encodes a predicted membrane-associated protein with diguanylate cyclase activity. Consistent with that activity, introduction into V. fischeri of medium-copy plasmids carrying these genes inhibited motility. Furthermore, multicopy expression of mifA induced other phenotypes known to be correlated with diguanylate cyclase activity, including cellulose biosynthesis and biofilm formation. To directly test their function, we introduced the wild-type genes on high-copy plasmids into Escherichia coli. We assayed for the production of cyclic di-GMP using two-dimensional thin-layer chromatography and found that strains carrying these plasmids produced a small but reproducible spot that migrated with an R_f value consistent with cyclic di-GMP that was not produced by strains carrying the vector control. Disruptions of mifA or mifB increased flagellin levels, while multicopy expression decreased them. Semiquantitative reverse transcription-PCR experiments revealed no significant difference in the amount of flagellin transcripts produced in either the presence or absence of Mg²⁺ by either vector control or mifA-overexpressing cells, indicating that the impact of magnesium and cyclic-di-GMP primarily acts following transcription. Finally, we present a model for the roles of magnesium and cyclic di-GMP in the control of motility of V. fischeri.

Published ahead of print on 15 September 2006.

This article has been cited by other articles:

• Darnell, C. L., Hussa, E. A., Visick, K. L. (2008). The Putative Hybrid Sensor Kinase SypF Coordinates Biofilm Formation in Vibrio fischeri by Acting Upstream of Two Response Regulators, SypG and VpsR. J. Bacteriol. 190: 4941-4950 [Abstract] [Full Text]  
• Hussa, E. A., Darnell, C. L., Visick, K. L. (2008). RscS Functions Upstream of SypG To Control the syp Locus and Biofilm Formation in Vibrio fischeri. J. Bacteriol. 190: 4576-4583 [Abstract] [Full Text]  
• Wolfe, A. J., Visick, K. L. (2008). Get the Message Out: Cyclic-Di-GMP Regulates Multiple Levels of Flagellum-Based Motility. J. Bacteriol. 190: 463-475 [Full Text]  
• Hussa, E. A., O'Shea, T. M., Darnell, C. L., Ruby, E. G., Visick, K. L. (2007). Two-Component Response Regulators of Vibrio fischeri: Identification, Mutagenesis, and Characterization. J. Bacteriol. 189: 5825-5838 [Abstract] [Full Text]  
• Kim, Y.-K., McCarter, L. L. (2007). ScrG, a GGDEF-EAL Protein, Participates in Regulating Swarming and Sticking in Vibrio parahaemolyticus. J. Bacteriol. 189: 4094-4107 [Abstract] [Full Text]  
• Visick, K. L., O'Shea, T. M., Klein, A. H., Geszvain, K., Wolfe, A. J. (2007). The Sugar Phosphotransferase System of Vibrio fischeri Inhibits both Motility and Bioluminescence. J. Bacteriol. 189: 2571-2574 [Abstract] [Full Text]