Adsorption of phage λ to Salmonella typhimurium lamB + requires the presence of lipopolysaccharide in the outer membrane

Summary Two S. typhimurium strains TA1534 (rfa ⁺) and TA1538 (rfaE) were transformed with the lamB expression plasmid pAMH70. Transposition events with placMu55 hybrid phage were successful only with TA1534/pAMH70 strain. Using SDS-PAGE, the LamB protein was present in the total cell proteins but not in the outer membrane proteins of the TA1538/pAMH70 strain. The LamB protein must linked to the LPS of the outer membrane to allow adsorption of phage in S. typhimurium.     

Use of flow cytometry to detect genotoxins by the Salmonella sulA-test

The Salmonella sulA-test using Salmonella typhimurium TA1538/pEM1968 ( sulA:: lacZ) is a new SOS-repair inducing system that detects mutagens and carcinogens. The b-galactosidase activity, currently detected by colorimetric dosage, can be measured by flow cytometry using a fluorescent substrate (fluorescein-di-b-D-galactopyranoside). Comparison of the dose-response relationships of eight chemicals determined by the two techniques showed that the Salmonella sulA-test combined with the flow cytometry technique was accurate and reliable as it covered a large number of cells in a short time.