Ribosomal helices: formation in Escherichia coli during acidic growth

Ribosomal helices are formed in 100% of Escherichia coli cells during extended growth in a medium of low buffering capacity. During this time, the pH of the medium gradually decreases from 7.0 to about 5.0. Transfer of cells into preconditioned or acidified medium does not result in helix formation unless acidification is gradual and during active growth. Concomitant with helix formation is a decrease of all major biosynthetic activities and cessation of cell motility. The larger polyribosomes become converted into an inactive helical form and sediment in sucrose gradients with the wall-membrane complex.