Control of the production of orthophosphate repressible extracellular enzymes in Neurospora crassa

Summary N-1, a plasmid isolated from a strain ofShigella flexneri in Japan more than 10 years ago, mediates the phage inhibition phenotype which has recently been found to be characteristic of plasmids of the H₂ incompatibility group. Using the criteria of phage inhibition, surface exclusion and incompatibility, the N-1 plasmid is shown to be closely related to H₂ plasmids isolated from non-typhoid salmonella and distantly related to H₁ plasmids isolated fromSalmonella typhi. Plasmids of other incompatibility groups did not show the H₂ type of phage inhibition.