Lysis of a temperature conditional thiamineless mutant of Salmonella typhimurium by glucose and other hexoses.

The SM-3 mutant of Salmonella typhimurium was isolated as streptomycin resistant and temperature conditional thiamine auxotroph. At 37 C it required thiamine, although it behaves as a leaky mutant at this temperature in minimal liquid medium. At 30 degrees C it was able to growth without thiamine. In minimal-glucose-aminoacids at 37 C after an initial growth, cellular lysis occurred. The same happened with other hexoses, but it was not observable when glycerol or lactate were used as carbon source. Microscopic examination showed clumps of cellular debris, empty bagshapes and swelling of microorganisms, suggesting a cell wall defect. Sucrose 0.5 M protected SM-3 cells from osmotic fragility. At 30 C growth was normal and at 37 C in presence of exogenous thiamine full growth without bacteriolysis was obtained. Preliminary experiments of bacterial conjugation allowed the identification of a new locus involved in thiamine biosynthesis which was tentatively mapped in the pur A - pro B region of the chromosomal map of S. typhimurium.