Mapping of genes involved in the synthesis of spermidine in Escherichia coli
The mapping of three genes (speA, speB and metK) involved in the biosynthesis of spermidine is described. They are located between minutes 56 and 57 on the linkage map of Escherichia coli. The clustering of these genes suggests the possibility of an operon for spermidine synthesis. Two other genes, argP, controlling the production of an arginine permease, and can, conferring resistance to canavanine, were found to be located in the same region.
In the course of studying the susceptibility of mice to Salmonella infection, we discovered that C3H/HeJ mice differ from other strains in both their susceptibility to infection and their response to prior vaccination. Others have noted the absence of the usual B cell stimulation by LPS in these mice. To investigate the status of delayed hypersensitivity in C3H/HeJ mice, we tried to use the technique of macrophage migration. Under conditions of normal migration for other strains, C3H/HeJ peritoneal and splenic macrophages failed to migrate, thus establishing another differentiating immunological trait for this strain.