Comparative study on central metabolic fluxes of Bacillus megaterium strains in continuous culture using 13C labelled substrates

Abstract

Fluxes of central carbon metabolism [glycolysis, pentose phosphate pathway (PPP), tricarboxylic acid cycle (TCA cycle), biomass formation] were determined for several Bacillus megaterium strains (DSM319, WH320, WH323, MS941) in C- and N-limited chemostat cultures by (13)C labelling experiments. The labelling patterns of proteinogenic amino acids were analysed by GC/MS and therefrom flux ratios at important nodes within the metabolic network could be calculated. On the basis of a stoichiometric metabolic model flux distributions were estimated for the different B. megaterium strains used at various cultivation conditions. Generally all strains exhibited similar metabolic flux distributions, however, several significant changes were found in (1) the glucose flux entering the PPP via the oxidative branch, (2) the reversibilities within the PPP, (3) the relative fluxes of pyruvate and acetyl-CoA fed to the TCA cycle, (4) the fluxes around the pyruvate node involving a futile cycle.

Metabolic fluxes in the central carbon metabolism of Dinoroseobacter shibae and Phaeobacter gallaeciensis, two members of the marine Roseobacter clade

“…2 and 3) revealed that the use of the ED pathway amounts to >99%, whereas glycolysis and PPP contribute only <1% (Table 2). Compared to other microorganisms such as E. coli [20], B. subtilis [21], B. megaterium [18] or C. glutamicum [22] grown on glucose, this is a rather unusual flux pattern. Most organisms use glycolysis and the pentose phosphate pathway concomitantly but at varying ratios (Table 2).…”

Bacillus megaterium—from simple soil bacterium to industrial protein production host

“…The experimental set up is shown in figure 6. When metabolic steady-20 state conditions were achieved, the feed medium, containing naturally labelled glucose as carbon source, was changed to an identical medium comprising a mixture of naturally and 13 C-enriched glucose (Fürch et al 2006;Fürch et al 2007). …”

“…Interestingly, the gluconeogenic reaction catalyzed by phosphoenolpyruvate carboxykinase was proven not to be active in all cases tested (Fürch et al 2006;Fürch et al 2007). 10…”

A short story about a big magic bug

“…The models have been confronted with the results from metabolome and fluxome analyses. 46,47 Consequently now, DNA microarray and proteomic experiments are the experi mental validation for the proposals. Furthermore, integration of regulatory and metabolic networks is desired.…”