Control over enzymatic activity in TCA cycle is highly regulated according to the energy state of the cell.
ATP, NADH, Acetyl CoA inactivate, while ADP and Pyruvate activate.
TCA cycle intermediates are used in diverse biosynthetic reactions.
To determine if TCA cycle inactivation altered capsule biosynthesis, capsule accumulation was quantified from equivalent numbers of bacteria (1.25 optical density at 660 nm [OD660] units) grown overnight in tryptic soy broth, using capsule immunoblots essentially as described previously (), except that immunoblots were developed using a chemiluminescent horseradish peroxidase (HRP) substrate (Millipore). Consistent with the hypothesis that post-exponential-growth-phase capsule biosynthesis requires TCA cycle activity, inactivation of any of the first three genes of the TCA cycle (citZ, acnA-citB, or citC) dramatically reduced capsule type 5 accumulation in strain SA564 (Fig. ). Similarly, inactivation of the aconitase gene (acnA-citB) in strain UAMS-1 strongly inhibited capsule type 8 accumulation (Fig. ). To determine if TCA cycle inactivation impaired PNAG synthesis, PNAG immunoblot analyses were preformed as described previously (). As expected, TCA cycle inactivation did not impair PNAG synthesis by strain UAMS-1 (Fig. ). (Strain SA564 does not produce PNAG under any growth conditions [C. Vuong and G. A. Somerville, unpublished observations]; thus, its ability to synthesize PNAG was not assessed.) These data demonstrate that the post-exponential-growth-phase biosynthesis of capsule requires TCA cycle activity.
Solid-phase oligonucleotide synthesis - ATDBio
These results suggest that nutrients are directed mainly into the tricarboxylic acid (TCA) cycle for cell growth rather than into P4HB synthesizing pathway.