NUTRITION AND METABOLISM OF MARINE BACTERIA: XIV. ON THE MECHANISM OF LYSIS OF A MARINE BACTERIUM

Abstract

Electron micrographs of thin sections of cell envelope preparations of a marine pseudomonad suspended in 0.5 M NaCl showed the presence of two unit membranes at the periphery. When suspended in 0.01 M NaCl the two membranes became infinitely separated and both non-dialyzable and dialyzable material appeared in solution. The composition of the non-dialyzable fraction indicated that it was derived from a mucopeptide layer. This layer was not visualized but at a high enough salt concentration is believed to lie between the two unit membranes and to play a role in holding the membranes together. Both heated and unheated envelope suspensions released hexosamine-containing material at low salt concentration. Lowering the salt concentration of the suspension caused an immediate rise in pH of the suspending solution. The effects of temperature and salts on the release of the hexosamine-containing fraction were analogous to the effects of temperature and salts on the denaturation of a polyanion and are explainable in terms of polyelectrolyte theory. It is suggested that the mucopeptide layer of this organism is made up of units which form a continuous layer only if their negative charges are screened by the cations of a salt. Loss of this layer would weaken the wall to the point where the intracellular osmotic pressure would cause the remaining membranes to rupture.