2015 article comments:

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J Bacteriol. 2015
Acetate Exposure Determines the Diauxic Behavior of Escherichia coli during the Glucose-Acetate Transition
Enjalbert B, Cocaign-Bousquet M, Portais JC, Letisse F

Growth of Escherichia coli on excess glucose under aerobic conditions is not diauxic (Wolfe AJ. 2005), and the acetate switch is certainly not "classically described as a diauxie".  It is therefore extraordinary that the authors are now showing that "diauxic behavior does not occur under such conditions".  A diauxie in the presence of both glucose and acetate in the culture medium was reported by Kao KC, 2005.

This comment by M. Crasnier-Mednansky (martine [at] minst [dot] org) was originally posted on Jan 16, 2017 at PubMed Commons

Trends Microbiol. 2015
Evolution of bacterial transcription factors: how proteins take on new tasks, but do not always stop doing the old ones
Visweswariah SS, Busby SJ

This review should have discussed transcription-coupled DNA supercoiling.  Ma J, 2013 demonstrated that RNAP was fully capable of melting DNA at random, and indicated that RNAP-generated (-) supercoiling may facilitate initiation of transcription at adjacent promoters and binding of regulatory proteins.  This agrees with the proposal CRP-cAMP has a preferential affinity for negatively supercoiled promoters.  The same authors also indicated in vivo transcription-generated supercoiling may potentially dissociate DNA-bound proteins even at a distance. Thus current understanding suggests RNAP itself may have evolved to be a master regulator of gene expression.  Simply said, transcriptional regulators do not recruit RNAP, they are recruited by RNAP.

This comment by M. Crasnier-Mednansky (martine [at] minst [dot] org) was originally posted on Sep 6, 2015 at PubMed Commons.  Note this comment does not discard the activation of transcription through the class I recruitment mechanism, that is the localized recruitment of RNAP by CRP.

J Bacteriol. 2015
A mannose family phosphotransferase system permease and associated enzymes are required for utilization of fructoselysine and glucoselysine in Salmonella enterica serovar Typhimurium
Miller KA , Phillips RS , Kilgore PB , Smith GL , Hoover TR

The present finding that Salmonella typhimurium transports fructoselysine via a mannose-type PTS (PTSGfr: Enzyme IIAGfr, IIBGfr, IICGfr and IIDGfr), and uses fructoselysine as a nitrogen source when growing on glucose, deserves some scrutiny.  The model established by Doucette CD, 2011 allows coordinated uptake of carbon and nitrogen via inhibition of Enzyme I by α-ketoglutarate, which accumulates in nitrogen limitation.  This strategy when applied to the present finding indicates that, when growth occurs on glucose and fructoselysine, both glucose and fructoselysine PTS transports must be regulated to prevent conditions of nitrogen limitation, which will result in both PTS being inhibited.  It was reported that the nitrogen PTS, PTSNtr (Enzyme INtr, NPr, and Enzyme IIANtr), is activated by α-ketoglutarate (Lee CR, 2013).  In this context, it is very tempting to propose that the PTS could function to regulate the transcription of the RpoN-dependent gfr operon. Thus, a controlled balance might occur for coordinating PTS-dependent carbon and nitrogen uptakes.

This comment by M. Crasnier-Mednansky (martine [at] minst [dot] org) was originally posted on July 23, 2015 at PubMed Commons

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