title: Tar-dependent and -independent pattern formation by Salmonella typhimurium.
abstract: When Salmonella typhimurium cells were allowed to swarm on either a minimal or complex semisolid medium, patterns of cell aggregates were formed (depending on the thickness of the medium). No patterns were observed with nonchemotactic mutants. The patterns in a minimal medium were not formed by a mutant in the aspartate receptor for chemotaxis (Tar) or by wild-type cells in the presence of alpha-methyl-D,L-aspartate (an aspartate analog), thus resembling the patterns observed earlier in Escherichia coli (E. O. Budrene and H. C. Berg, Nature [London] 349:630-633, 1991) and S. typhimurium (E. O. Budrene and H. C. Berg, Abstracts of Conference II on Bacterial Locomotion and Signal Transduction, 1993). Distinctively, the patterns in a complex medium had a different morphology and, more importantly, were Tar independent. Furthermore, mutations in any one of the genes encoding the methyl-accepting chemotaxis receptors (tsr, tar, trg, or tcp) did not prevent the pattern formation. Addition of saturating concentrations of the ligands of these receptors to wild-type cells did not prevent the pattern formation as well. A tar tsr tcp triple mutant also formed the patterns. Similar results (no negative effect on pattern formation) were obtained with a ptsI mutant (defective in chemotaxis mediated by the phosphoenolpyruvate-dependent carbohydrate:phosphotransferase system [PTS]) and with addition of mannitol (a PTS ligand) to wild-type cells. It therefore appears that at least two different pathways are involved in the patterns formed by S. typhimurium: Tar dependent and Tar independent. Like the Tar-dependent patterns observed by Budrene and Berg, the Tar-independent patterns could be triggered by H(2)O(2), suggesting that both pathways of pattern formation may be triggered by oxidative stress.
authors.affiliation: Department of Membrane Research and Biophysics, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: Y
authors.initials: Y
authors.lastname: Blat
authors.forename: M
authors.initials: M
authors.lastname: Eisenbach
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology*; D002628:Chemoreceptor Cells; D003470:Culture Media; D029968:Escherichia coli Proteins; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008565:Membrane Proteins / Q000502:physiology*; D011956:Receptors, Cell Surface; D012486:Salmonella typhimurium / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; C057331:Tar protein, E coli; D006861:Hydrogen Peroxide