Transient expression and flux changes during a shift from high to low riboflavin production in continuous cultures of Bacillus subtilis.
At the onset of glucose-limited continuous cultures, riboflavin production in recombinant Bacillus subtilis declines significantly within 3 generations. This phenomenon was specific to riboflavin production and was not correlated with any other physiological parameter. Physiological analyses excluded genetic degeneration or co-metabolism of previously generated overflow metabolites as possible causes for the riboflavin transients. By developing a novel method for (13)C-based metabolic flux analysis under non-steady-state conditions, we showed that the pentose precursors of riboflavin were exclusively synthesized via the non-oxidative pentose-phosphate (PP) pathway as long as riboflavin production was high. The complete redirection of carbon flux to the oxidative branch of the PP pathway was achieved at unaltered PP pathway gene expression and correlated with the declining riboflavin production. With the possible exception of a slight down-regulation of the purine biosynthesis pathway, genome-wide expression analysis indicated that transcriptional regulation was not responsible for the production decline.
Zamboni
Nicola
N
Institute of Biotechnology, ETH Zürich, CH-8093 Zürich, Switzerland.
Fischer
Eliane
E
Muffler
Andrea
A
Wyss
Markus
M
Hohmann
Hans-Peter
HP
Sauer
Uwe
U
D001412:Bacillus subtilis / Q000502:physiology*; D018929:Cell Culture Techniques / Q000379:methods; D049109:Cell Proliferation; D003198:Computer Simulation; D004734:Energy Metabolism / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D005947:Glucose / Q000378:metabolism*; D008954:Models, Biological; D015202:Protein Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000096:biosynthesis; D012256:Riboflavin / Q000096:biosynthesis* / Q000235:genetics*; D015398:Signal Transduction / Q000502:physiology*; D013997:Time Factors
D011994:Recombinant Proteins; D005947:Glucose; D012256:Riboflavin