- Swarming motility
"Swarming motility" is a rapid (2-10 μm/s.) and coordinated translocation of a bacterial population across solid or semi-solid surfaces. This type of motility is an example of an emerging concept in microbiology :
bacterial multicellularity . Swarming motility was first reported by Jorgen Henrichsen [cite web|url=Henrichsen,|title=J. (1972) Bacteriol. Rev. 36, 478-503.] and has been mostly studied in genus "Serratia " [cite web|url=Alberti,|title=L. & Harshey, R. M. (1990) J. Bacteriol. 172, 4322-4328.] [cite web|url=Eberl,|title=L., Molin, S., & Givskov, M. (1999) J. Bacteriol. 181, 1703-1712.] , "Salmonella "cite web|url=Harshey,|title=R. M. (1994) Mol. Microbiol. 13, 389-394.] , "Aeromonas " [cite web|url=Kirov,|title=S. M., Tassell, B. C., Semmler, A. B., O'Donovan, L. A., Rabaan, A. A., & Shaw, J. G. (2002) J. Bacteriol. 184, 547-555.] , "Bacillus " [cite web|url=Kearns,|title=D. B. & Losick, R. (2003) Mol. Microbiol. 49, 581–590.] , "Yersinia" [cite web|url=Young,|title=G. M., Smith, M. J., Minnich, S. A., & Miller, V. L. (1999) J. Bacteriol. 181, 2823-2833.] , "Pseudomonas " [cite web|url=Déziel,|title=É., Lépine, F., Milot, S., & Villemur, R. (2003) Microbiol. 149, 2005-2013.] [cite web|url=Tremblay,|title=J., Richardson, A.-P., Lépine, F., & Déziel, É. (2007) Environ. Microbiol. 9, 2622-2630.] cite web|url=Kohler,|title=T., Curty, L. K., Barja, F., van Delden, C., & Pechere, J. C. (2000) J. Bacteriol. 182, 5990-5996.] cite web|url=Rashid,|title=M. H. & Kornberg, A. (2000) Proc. Natl. Acad. Sci. U. S. A. 97, 4885-4890.] [cite web|url=Caiazza,|title=N. C., Shanks, R. M. Q., & O’Toole, G. A. (2005) J. Bacteriol. 187, 7351-7361.] , "Proteus " [cite web|url=Rather,|title=P. N. (2005) Environ Microbiol 7, 1065-1073.] , "Vibrio " [cite web|url=McCarter,|title=L. & Silverman, M. (1990) Mol. Microbiol. 4, 1057-1062.] [cite web|url=McCarter,|title=L. L. (2004) J Mol Microbiol Biotechnol 7, 18-29.] and "Escherichia " [cite web|url=Harshey,|title=R. M. & Matsuyama, T. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 8631-8635.] [cite web|url=Burkart,|title=M., Toguchi, A., & Harshey, R. M. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 2568-2573.] .This multicellular behavior has been mostly observed in controlled laboratory conditions and relies on two critical elements: 1) the nutrient composition and 2) viscosity of culture medium (i.e. % agar) ] . One particular feature of this type of motility is the formation of dendritic fractal-like patterns formed by migrating swarms moving away from an initial location. Although the majority of species can produce tendrils when swarming, some species like "
Proteus mirabilis " do form concentric circles motif instead of dendritic patterns.Biosurfactant, quorum sensing and swarming
In some species, swarming motility requires the self-production of
biosurfactant to occur [cite web|url=Daniels,|title=R., Vanderleyden, J., & Michiels, J. (2004) FEMS Microbiol. Rev. 28, 261-289.] ] .Biosurfactant synthesis is usually under the control of an intercellular communication system calledquorum sensing . Biosurfactant molecules are thought to act by lowering surface tension, thus permitting bacteria to move across a surface.Cellular differentiation
Swarming bacteria undergo morphological differentiation that distinct them from their planktonic state. Cells localized at migration front are typically hyperelongated, hyperflagellated and grouped in multicellular raft structures [cite web|url=Julkowska,|title=D., Obuchowski, M., Holland, B., & Séror, S. J. (2004) Microbiol. 150, 1839–1849.] ] ] .
Ecological significance
The fundamental role of swarming motility remains unknown. However, it has been observed that active swarming bacteria of "
Salmonella typhimurium " shows an elevated resistance to certain antibiotics compared to undifferentiated cells [cite web|url=Kim,|title=W., Killam, T., Sood, V., & Surette, M. G. (2003) J. Bacteriol. 185, 3111–3117.] .References
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