However, other mechanisms can also be involved in Acs down-regulation, for example by Cra.
We observed the beginning of carbon catabolite repression (CCR) induction prior to acetate accumulation in parallel with Acs down-regulation.
As a result, it is proposed that acetate overflow metabolism in E. coli is triggered by Acs down-regulation resulting in decreased assimilation of acetic acid produced by Pta, and disruption of the PTA-ACS node.
Concerning Acs down-regulation, it is possible that CCR is responsible for its repression as proposed by Treves et al. [ 46] showing the link between ACS expression level and acetate accumulation.
In particular, they propose that acetate overflow metabolism in E. coli is triggered by the disruption of the PTA-ACS node, namely acetyl-CoA synthetase (ACS) down-regulation results in decreased assimilation of acetate via phosphotransacetylase (PTA).
As it is well known that CCR is initiated by the presence of glucose in the medium [ 49, 50], we propose that increasing residual glucose concentration accompanying smooth rise of dilution rate in A-stat triggers Acs down-regulation by CCR.
As Acs down-regulation is responsible for triggering overflow metabolism and the resulting accumulation of acetate is detrimental to cellular growth, it bears questioning why E. coli has not evolved towards maintaining sufficient Acs levels for acetate assimilation in all growth conditions.
A bit later, he draws an arm across his body in a Napoleon Bonaparte-like gesture, his sign for "It's cold in here, turn the AC down!" The gestures are so Max.
We found that these 87 ECD AC down-regulated genes could be consisting of a novel immune system signature of AC (S1e in Additional file ).
The temporal accumulation of yar in D. virilis embryos was reminiscent of D. melanogaster, with transcription of yar coinciding with ac down-regulation and transcription of y coinciding with yar down-regulation.
For the case of AC down-regulated categories, significant categories include immunity and defence, interleukin signalling pathway, mesoderm development, cell structure and motility, signal transduction, cell surface receptor mediated signal transduction, cell communication, intracellular signalling cascade, cell structure cell adhesion, cell motility.
