The Lysis of a Psychrophilic Marine Bacterium as Studied by Microelectrophoresis

Abstract

Non-growing cells of a psychrophilic marine bacterium lyse if subjected to temperatures above 21 °C, to low ionic strengths, or to pH values below 6.0. Microelectrophoretic techniques were used to help determine the surface effects of cellular breakdown. During lysis, however induced, the cell populations became heterogeneous in mobility. This was apparently due to the adsorption of intracellular material, with a higher negative charge than intact cells, onto the cell surface. The mobilities of cells lysed in water or at acid pH reverted to the control values after repeated washings, which were thought to remove adsorbed intracellular material. Lysis induced by these latter treatments, therefore, did not involve the external cell surface. Water-lysed cells were stable at temperatures where both whole cells and mechanically prepared cell envelopes were subject to breakdown. After temperature-induced lysis, the washed cells possessed a higher negative mobility than intact cells, which was not due to the presence of adsorbed intracellular material, but rather to an irreversible surface change. Lysis in distilled water at 25 °C left the cell surface unchanged, and the "temperature effect" of a permanently increased negative charge was only evident when lysis at 25 °C preceded exposure to distilled water.

Structural Changes During Lysis of a Psychrophilic Marine Bacterium

“…The isoelectric point of this bacterium lies between pH 2.0 and 2.5 (18), indicating that its cell walls contain excess acidic groups. The ability of Na+ and Mg2+ to stabilize the wall could be due to their masking mutually repulsive negative charges and conferring greater stability to the cell wall.…”

“…Because it has only a single polar flagellum, this classification is unsuitable. For stability, the red psychrophile needs low temperatures, pH values near neutrality, and both monovalent and divalent cations (11,14,18). In contrast to other marine bacteria, its structure is poorly maintained by monovalent salts and even more poorly by nonionic solutes (14,17).…”

“…Previous work from our group was concerned with the physiology of a red-pigmented psychrophilic marine bacterium, NRC 1004 (11,14,18). This short, gram-negative motile rod grows in a temperature range of 0 to 19 C. At higher temperatures, death and lysis occur rapidly (I I), accompanied by a release of hexosamines and a degradation of lipid phosphorus, presumably through the action of a cell-bound phosphatidase (11,14).…”

“…Cells are also lysed by low ionic strength or acid pH values. The surface effects of different kinds of lysis were studied by microelectrophoresis (18).…”

Psychrophilic bacteria.

“…5). Salt and low temperature are necessary for the stability of the cellular structure of V. psychroerythrus (40,94), and lysis can occur at low ionic strength (108). V. psychroerythrus is stable in cold sea water or in a solution containing 0.1 M Mg2+ and 0.5 M NaCl.…”