The Effect of Culture Age, Chloramphenicol and B6 Inhibitors on Intra- and Extracellular Keto and Amino Acids of Escherichia coli B

Abstract

S U M M A R YKeto acids and free amino acids were assayed in the cells and the medium of Escherichia coli B growing in the presence of chloramphenicol, cycloserines, aminooxyacetate, and limiting nitrogen source.Under these growth-limiting conditions the cells accumulated ketoglutarate and 'ketovaline' but no other keto acids. In all experiments only ketoglutarate, pyruvate, and 'ketovaline' were found in the medium. Amino acids are released into the medium in the early phases of growth and the composition of the extracellular amino acids is similar to that of the amino acid pool. The concentrations of free amino acids were 103-104 times higher in the cell than in the medium. The internal pool composition is fixed under all growth-limiting conditions. In the presence of the drugs the cells release amino acids into the medium.

Chemotaxis toward amino acids by Bdellovibrio bacteriovorus

“…It is unlikely that B. bacteriovorus locates individual or small populations of prey cells by means of chemotaxis toward amino acids. Although bacteria such as E. coli do excrete amino acids, particularly alanine, glycine, glutamate, serine, and valine, the levels excreted by 7 x 108 cells/ml are in the range of 0.2 to 5.8 ,uM (12). These levels are too low to be detected by B. bacteriovorus.…”