Kinetics of uptake and incorporation of meso-diaminopimelic acid in different Escherichia coli strains
The rate at which the peptidoglycan precursor meso-diaminopimelic acid (DAP) is incorporated into the cell wall of Escherichia coli cells was determined by pulse-label experiments. For different E. coli strains, the incorporation rate was compared with the rate of uptake of DAP into the cell. With E. coli W7, a dap lys mutant generally used in this kind of studies, steady-state incorporation was reached only after about 0.75 of the doubling time. This lag period can be ascribed to the presence of a large internal DAP pool in the cells. An E. coli K-12 lysA strain was constructed which could be grown without DAP in its medium. Consequently, due to the higher specific activity of the added (TH)DAP, faster incorporation and higher levels of radioactivity in the peptidoglycan layer were observed in the K-12 lysA strain than in the W7 strain. In addition, uptake and incorporation were faster in steady state (within about 0.2 of the doubling time), indicating a smaller DAP pool. The lag period could be further diminished and the incorporation rate could be increased by feedback inhibition of the biosynthetic pathway to DAP with threonine and methionine. These results make MC4100 lysA a suitable strain for studies on peptidoglycan synthesis. To explain our observations, the authors suggest the existence of an expandable pool of DAP in E. coli which varies with the DAP concentration in the growth medium.
- Research Organization:
- Univ. of Amsterdam, Netherland
- OSTI ID:
- 6298091
- Journal Information:
- J. Bacteriol.; (United States), Vol. 1
- Country of Publication:
- United States
- Language:
- English
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