Application of31P nuclear magnetic resonance spectroscopy to investigate plasmid effects onEscherichia coli metabolism

Summary Glucose metabolism inE. coli strain HB101, as a plasmid-free cell and as a host to two plasmids of different copy numbers, has been characterized using³¹P NMR. While the low-copy-number strain was found to behave very similarly to the plasmid-free strain, dramatically different behavior was exhibited by the high-copy-number strain. This strain maintained a nearly constant intracellular pH after addition of glucose to a starved suspension while intracellular pH of the other strains dropped considerably. The inorganic phosphate level in the high-copy-number strain was substantially higher than in the other strains, and the NTP level was much lower. Glycolytic rates of all three strains, however, were nearly identical. The trend in glycolytic rate strongly suggests that transport of glucose into the cell is the rate-limiting step under these conditions.