Conditional mutations affecting the cell envelope ofEscherichia coliK-12

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Abstract
SUMMARY: Amongst a collection of temperature sensitive (TS) mutants ofEscherichia coliK-12, some have been found which can grow at the restrictive temperature (42 °C) if the osmotic pressure of the medium is raised by the addition of sodium chloride (1%) or sucrose (12·5%). These mutants are described as temperature sensitive osmotic remedial (TSOR) mutants. At the restrictive temperature they are not osmotically fragile, but do display decreased resistance to inhibitory agents such as deoxycholate, actino-mycin D and acridine orange; they also show release of the periplasmic enzyme ribonuclease. These results indicate a change in the cell's outer permeability barrier. The genes affected in six of the mutants have been located on theE. colilinkage map. The mutations, which occur at loci not previously described, have been namedenvM–envTto indicate their effect on the cellenvelope.