Exacting predictions by cybernetic model confirmed experimentally: steady state multiplicity in the chemostat.
We demonstrate strong experimental support for the cybernetic model based on maximizing carbon uptake rate in describing the microorganism's regulatory behavior by verifying exacting predictions of steady state multiplicity in a chemostat. Experiments with a feed mixture of glucose and pyruvate show multiple steady state behavior as predicted by the cybernetic model. When multiplicity occurs at a dilution (growth) rate, it results in hysteretic behavior following switches in dilution rate from above and below. This phenomenon is caused by transient paths leading to different steady states through dynamic maximization of the carbon uptake rate. Thus steady state multiplicity is a manifestation of the nonlinearity arising from cybernetic mechanisms rather than of the nonlinear kinetics. The predicted metabolic multiplicity would extend to intracellular states such as enzyme levels and fluxes to be verified in future experiments.
School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA.
Jin Il
JI
Kim
Hyun-Seob
HS
Song
Sunil R
SR
Sunkara
Arvind
A
Lali
Doraiswami
D
Ramkrishna
D019149:Bioreactors / Q000382:microbiology; D003470:Culture Media / Q000737:chemistry / Q000378:metabolism; D003491:Cybernetics; D004926:Escherichia coli / Q000737:chemistry* / Q000254:growth & development / Q000378:metabolism*; D005947:Glucose / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D008962:Models, Theoretical; D019289:Pyruvic Acid / Q000737:chemistry / Q000378:metabolism
D003470:Culture Media; D019289:Pyruvic Acid; D005947:Glucose