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J Bacteriol. 1971 November; 108(2): 916-927
Copyright © 1971 American Society for Microbiology. All Rights Reserved.

Structural Changes During Lysis of a Psychrophilic Marine Bacterium¹

^a Department of Biology, University of Ottawa, Ottawa, KIN 6N5, Ontario, Canada

ABSTRACT

The marine psychrophile, a red, gram-negative motile rod with a single polar flagellum, is stable when suspended in 0.1 M Mg²⁺ plus 0.5 M NaCl at 0 C and neutral pH but lyses if the salt composition of the medium is changed, the temperature raised above 20 C, or the pH lowered. Lysis is accompanied by a fall in turbidity, a release of ultraviolet-absorbing substances, and a loss of deoxyribonucleic acid and ribonucleic acid. Ultrastructural changes accompanying lysis were studied. Thin sections of cells fixed while intact showed a triple-layered cell wall and cytoplasmic membrane, each 6.0 to 7.5 nm thick. Mesosomes were also observed. Either Na⁺ or Mg²⁺ could maintain wall integrity, whereas Mg²⁺ was needed for membrane integrity. In distilled water, lysis was very extensive, and much material was released as wall fragments and as vesicles which probably came from the wall and cytoplasmic membrane. Lysis at 37 C resulted in degradation of the wall and liberation of wall fragments. The cell membrane was rarely observed as a triple-layered structure in such temperature-lysed cells. After lysis at pH 5.0, the cell wall was distorted, and only a suggestion of the cell membrane remained. Replicas showed that this organism had a matted surface which was distorted under different conditions of lysis.

¹ A preliminary report of some of these findings was presented at the 71st Annual Meeting of the American Society for Microbiology, Minneapolis, Minn., 2-7 May 1971.