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J. Bacteriol., 02 1996, 1113-1119, Vol 178, No. 4
W Shi, BA Stocker and J Adler
We have reported that motile Escherichia coli K-12 placed in an electric
field swims toward the anode but that motile Salmonella typhimurium strains
swim toward the cathode, a phenomenon called galvanotaxis (J. Adler and W.
Shi, Cold Spring Harbor Symp. Quant. Biol. 53:23-25, 1988). In the present
study, we isolated mutants with an altered direction of galvanotaxis. By
further analyses of these mutants and by examination of E. coli and
Salmonella strains with altered cell surface structure, we have now
established a correlation between the direction of galvanotaxis and the
surface structure of the cell: motile rough bacteria (that is, those
without O polysaccharide; for example, E. coli K-12 and S. typhimurium
mutants of classes galE and rfa) swam toward the anode, whereas motile
smooth bacteria (that is, those with O polysaccharide; for example,
wild-type S. typhimurium LT2) swam toward the cathode. However, smooth
bacteria with acidic polysaccharide capsules (K1 in E. coli and Vi in
Salmonella typhi) swam toward the anode. Measurements of passive
electrophoretic mobility of strains representative of each set were made.
We propose that the different directions of galvanotaxis of rough (or
capsulate) bacteria and of smooth bacteria are explicable if the negative
electrophoretic mobility of flagellar filaments is less than that of rough
bodies but greater than that of smooth bodies.
Copyright © 1996, American Society for Microbiology
Effect of the surface composition of motile Escherichia coli and motile Salmonella species on the direction of galvanotaxis
Department of Biochemistry, University of Wisconsin-Madison 53706, USA.
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