TEMPERATURE-SENSITIVE, LIPOPOLYSACCHARIDE-DEFICIENT MUTANTS OF SALMONELLA-TYPHIMURIUM

Two mutants of Salmonella typhimurium LT2, which were temperature-sens itive for lipopolysaccharide (LPS) synthesis, were isolated from a gal E(-) strain based on their resistance to phage C21 and sensitivity to sodium deoxycholate at 42 degrees C. They produced LPS of chemotype Re at 30 degrees C and deep-rough LPS at 42 degrees C. P22-mediated tran sductional analysis showed that the mutations responsible for temperat ure sensitivity are located in the rfa cluster where several genes inv olved in the synthesis of the LPS core are mapped. A plasmid, carrying rfaC, D and F genes of Escherichia coli K-12, complemented these muta tions. These genes are responsible for the synthesis of the inner-core region of the LPS molecule. This indicates that genetic defects in th ese temperature-sensitive mutants affect the inner-core region of LPS.