ParD: a new gene coding for a protein required for chromosome partitioning and septum localization in Escherichia coli.

A new gene, parD, has been located at 88.5 min on the genetic map of E. coli. Cells carrying an amber mutation in this gene, together with a temperature-sensitive suppressor tRNA, are able to grow, synthesize DNA and divide at both 30 degrees C and 42 degrees C. At 42 degrees C, however, they are defective both in the separation of replicated chromosomes and in the placement of septa. Both the amount of DNA and the number of septa per cell mass are normal in cells growing at 42 degrees C: only the localization of the chromosomes and septa are altered. As a result, cells of random sizes are produced at 42 degrees C and the smallest of these contain no DNA.