Carbon isotopic fractionation in heterotrophic microbial metabolism.
Differences in the natural-abundance carbon stable isotopic compositions between products from aerobic cultures of Escherichia coli K-12 were measured. Respired CO2 was 3.4% depleted in 13C relative to the glucose used as the carbon source, whereas the acetate was 12.3% enriched in 13C. The acetate 13C enrichment was solely in the carboxyl group. Even though the total cellular carbon was only 0.6% depleted in 13C, intracellular components exhibited a significant isotopic heterogeneity. The protein and lipid fractions were -1.1 and -2.7%, respectively. Aspartic and glutamic acids were -1.6 and +2.7%, respectively, yet citrate was isotopically identical to the glucose. Probable sites of carbon isotopic fractionation include the enzyme, phosphotransacetylase, and the Krebs cycle.
Blair
N
N
Leu
A
A
Muñoz
E
E
Olsen
J
J
Kwong
E
E
Des Marais
D
D
D000085:Acetates / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism; D002247:Carbon Isotopes; D002951:Citrates / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D007553:Isotope Labeling / Q000379:methods; D007700:Kinetics
D000085:Acetates; D002247:Carbon Isotopes; D002951:Citrates; D005971:Glutamates; D001224:Aspartic Acid; D018698:Glutamic Acid; D005947:Glucose