Corrigendum to “Modelling nitrogen assimilation of Escherichia coli at low ammonium concentration”[J. Biotechnol. 144 (2009) 175--183]

Hongwu Ma, Fred C Boogerd, Igor Goryanin

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The authors wish to notify that the part of the nitrogen assimilation model dealing with AmtB-mediated transport of ammonium across the cytoplasmic membrane contains an error. The set of reactions constituting ammonium transport (reactions rAN4, rAN3, rN3 and the external View the MathML source balance reaction: View the MathML source) does not comply with the detailed balance principle. The net reaction of these four reactions is NH3ex = NH3in. In particular, the product of the forward reaction constants should have equalled that of the backward reaction constants, that is, their ratio should equal 1, while it actually amounts to 3.6 in the model. Exactly for this reason, the model allows for intracellular NH3 accumulation (at most 3.6-fold) and the concomitant occurrence of negative NH3 diffusion. Thus, although the transport process was modelled according to what is known about the mechanism (without explicit reference to the driving force that is still a controversial issue), the reaction constants chosen implicitly caused ammonium transport to become a case of active transport. Consequently, at a kAmtB value of 2000 s−1, the steady-state ratio of the internal/external NH3 concentration in the model was 1.3 when besides active transport also nitrogen assimilation, passive NH3 permeation, G ln K activity, and ΔpH were taken into account (see Table 3).

The authors apologize for any confusion this error might have caused and thank Dr D. Molenaar for his critical alertness.
Original languageEnglish
Pages (from-to)207
Number of pages1
JournalJournal of Biotechnology
Issue number1
Publication statusPublished - 2010

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