PMID:1100857

Citation	Aswad, D and Koshland, DE (1975) Isolation, characterization and complementation of Salmonella typhimurium chemotaxis mutants.J. Mol. Biol. 97:225-35
Abstract	No abstract in PubMed
Links	PubMed
Keywords	Chemotaxis; Genes, Dominant; Genes, Recessive; Genetic Complementation Test; Genotype; Mutation; Recombination, Genetic; Salmonella typhimurium; Species Specificity
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Main Points of the Paper

Please summarize the main points of the paper.

• Isolation of non-chemotactic mutants
• Description of the preformed liquid gradient technique
  • utilizes a preformed gradient in a vertical column of liquid medium
  • separates wild-type, non-motile, and non-motile but chemotactic into 3 regions
• None of the 72 mutants isolated exhibited a frequency of spontaneous tumbling
  • 68 exhibited smooth co-ordinated motility with no evidence of tumbling
  • 4 exhibited uncoordinated motility
• Results suggest there may be as many as 6 genetically distinct classes of che mutants in Salmonella

Materials and Methods Used

Please list the materials and methods used in this paper (strains, plasmids, antibodies, etc).

• For the isolation of non-chemotactic mutants
  • preformed liquid gradient technique (described in detail)
  • Diethylsulfate mutagenesis
  • negative swarm selection on Tryptone semi-solid medium (0.3% agar)

1. culture spotted on plate
2. overnight incubation (wt bacteria swarmed outward from the inoculum, leaving a dense population at the center)
3. sample taken from the center of colony
4. perform 10 such serial selections
5. grow samples in nutrient broth and plate on Tryptone semisolid medium
6. 200 non-swarming colonies were picked and screened for motility by examination with a microscope

• For complementations and strain constructions
  • Alternative method of abortive transduction

• Strains
  • all strains were derived from Salmonella typhimurium LT2

Phenotype Annotations

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Species	Taxon ID	Strain	Gene (if known)	OMP	Phenotype	Details	Evidence	Notes
Salmonella typhimurium LT2	NCBI:99287	ST20			Motility	smooth motility with no spontaneous tumbling	Microscopy	isolated from using negative swarm selection described above. Phenotype labeled che-222(p)
Salmonella typhimurium LT2	NCBI:99287	ST20			Motility	consistently diffuses in the direction of gravity, regardless of attractant	Other	Preformed liquid gradient technique- Phenotype for this strain is labeled che-222(p)
Salmonella typhimurium LT2	NCBI:99287	ST1			Motility	moves in the direction of attractant	Other	Preformed liquid gradient technique
Salmonella typhimurium LT2	NCBI:99287	TA1859			Motility	no significant movement in either direction	Other	Preformed liquid gradient technique. This is a non-motile mutant strain.
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Notes

Controls for the preformed liquid gradient method were:

1. ST20 (non-chemotactic mutant strain described above)
2. TA1859 (non-motile mutant)
3. ST1 (wild type strain)