Summary: Mucopeptide synthesis in and mutants of has been examined by studying the incorporation of -acetyl[1-C]glucosamine. It has also been examined in a mutant by the incorporation of D-[1-C]alanine. In the latter the changes in the ester-linked -alanine of the teichoic acids was also studied. When the growth temperature for the mutant is changed from 30 to 45 °C and the organisms become round, mucopeptide synthesis is increased so that the bacteria finally contain 4 to 5 times as much mucopeptide per unit of dry weight. The change in rate of synthesis is immediate. The change in proportion of ester-linked alanine in the walls is entirely due to dilution of the existing material by additional mucopeptide. This suggests that the large reduction in the proportion of teichoic acid in the walls may similarly be due to dilution by increased mucopeptide. On changing the growth temperature from 45 to 30 °C the time course for the formation of mucopeptide is complicated, having an initial phase of rapid deceleration and a secondary phase of acceleration to a rate characteristic for the lower temperature. In both the shifts, up and down, the morphological changes accurately reflect the periods of maximum alteration in mucopeptide content. There are no similar changes in mutants, but a small reduction occurs in the specific activity of the mucopeptide--acetyl hexosamines, when -acetyl[1-C]-glucosamine is present in the medium and -glutamic acid is added to convert the round forms to rods. None of the changes occur in the parent organisms not carrying the mutations.


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