STUDIES ON NITRATE REDUCTION BY ESCHERICHIA COLI

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Abstract
Data given indicate the presence of a nitrate reducing system in non-proliferating E. coli B/r cells regardless of their growth in the presence or absence of nitrate or amino acids. The kinetics of nitrate reduction by nonproliferating suspensions of old cells from peptone medium with and without nitrate suggest an adaptive system. However, the high rate of nitrate reduction by their respective cell extracts points strongly toward a permeability barrier in old cells toward nitrate. A further indication for this conclusion were the results obtained using young cells which reduce nitrate vigorously at almost the same rate regardless of their previous history. The low nitrate reducing activity of both nonproliferating suspensions and extracts of cells grown on nitrateless synthetic medium suggest that peptone or nitrate may act as a stabilizer of the system in question.