![]() ![]() Cyd has a very high affinity for O 2, whereas Cyo has a lower affinity, but is energetically more efficient. It has two well-characterized terminal oxidases, Cyd and Cyo. The model bacterium Escherichia coli has a modular electron transport chain that allows it to successfully compete in environments with differing oxygen (O 2) availabilities. Analysis of FNR variants suggested that the monomer-dimer transition is the key step in FNR-mediated repression of gene expression. consumption of O 2 at the membrane by the terminal oxidases and reaction of O 2 with cytoplasmic FNR. The model implies that there are two barriers that dampen the response of FNR to O 2, i.e. The molecules of O 2, transcription factors and terminal oxidases are treated as individual agents and their behaviors and interactions are imitated in a simulated 3-D E. coli and the consequent modulation of ArcA and FNR activities based on experimental data obtained from highly controlled chemostat cultures. In this study, an agent-based modeling approach has been taken to spatially simulate the uptake and consumption of O 2 by E. It has been suggested that O 2-consumption by the terminal oxidases located at the cytoplasmic membrane significantly affects the activities of ArcA and FNR in the bacterial nucleoid. coli encounters environments with different O 2 availabilities, the expression of the genes encoding the alternative terminal oxidases, the cydAB and cyoABCDE operons, are regulated by two O 2-responsive transcription factors, ArcA (an indirect O 2 sensor) and FNR (a direct O 2 sensor). Two major terminal oxidases are involved in this process - Cyo has a relatively low affinity for O 2 but is able to pump protons and hence is energetically efficient Cyd has a high affinity for O 2 but does not pump protons. In the presence of oxygen (O 2) the model bacterium Escherichia coli is able to conserve energy by aerobic respiration.
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