On 2017 Apr 19, Martine Crasnier-Mednansky commented:

The authors have previously reported that very little SgrT is made in E. coli as compared to Salmonella typhimurium, which led them to conclude that E. coli K12 has "lost the need for SgrT" (Wadler CS, 2009). Later on, the rationale for using S. typhimurium instead of E. coli for studying SgrT was reinforced (Balasubramanian D, 2013). In the present work, the authors use E. coli sgrS mutant strains overproducing SgrT. Therefore, the present work does not establish a 'physiological' role for SgrT in preventing the E. coli PTS-transport of glucose, thus the title of the article is misleading.

The authors’ interpretation of figure 1 does not agree with the following data. E. coli mutant strains lacking Enzyme IICB^Glc (PtsG) do grow on glucose (see Curtis SJ, 1975; Table VIII in Stock JB, 1982). Mutant strains lacking both the glucose and mannose enzyme II grow very slowly on glucose. In other words, because growth had been observed on mannose, growth should have been observed on glucose. Furthermore, the authors should have been aware that an increased level of cAMP from overexpressing SgrT further impairs growth on glucose.

PtsG is not "comprised of three main functional domains", as the authors state. PtsG has two functional domains (IIB and IIC) connected by a flexible linker. In the nomenclature for PTS proteins (Saier MH Jr, 1992), PtsG translates into Enzyme IICB^Glc, which is informative (and therefore should be preferred to any other designations) because it indicates a two-domain structure, a specificity for glucose, and the order of the domains (from N to C terminus).

Kosfeld A, 2012 clearly established, by cross-linking experiments, the interaction between SgrT and Enzyme IICB^Glc in the presence of glucose. They also visualized the recruitment of SgrT to the membrane by in vivo fluorescence microscopy. It is therefore unwarranted for the authors to 'hypothesize' an interaction and localization to the membrane, and to state: "Once we established that SgrT inhibits PtsG specifically and its localization to the membrane …". In addition, the demonstration by Kosfeld A, 2012, the motif KTPGRED (in the flexible linker) is the main target for SgrT, is rather convincing.

Finally, the statement "SgrT-mediated relief of inducer exclusion may allow cells experiencing glucose-phosphate stress to utilize alternative carbon sources" is inaccurate because it ignores the positive effect of cAMP on the utilization of alternative carbon sources like lactose.

On 2017 Apr 19, Martine Crasnier-Mednansky commented:

The authors have previously reported that very little SgrT is made in E. coli as compared to Salmonella typhimurium, which led them to conclude that E. coli K12 has "lost the need for SgrT" (Wadler CS, 2009). Later on, the rationale for using S. typhimurium instead of E. coli for studying SgrT was reinforced (Balasubramanian D, 2013). In the present work, the authors use E. coli sgrS mutant strains overproducing SgrT. Therefore, the present work does not establish a 'physiological' role for SgrT in preventing the E. coli PTS-transport of glucose, thus the title of the article is misleading.

The authors’ interpretation of figure 1 does not agree with the following data. E. coli mutant strains lacking Enzyme IICB^Glc (PtsG) do grow on glucose (see Curtis SJ, 1975; Table VIII in Stock JB, 1982). Mutant strains lacking both the glucose and mannose enzyme II grow very slowly on glucose. In other words, because growth had been observed on mannose, growth should have been observed on glucose. Furthermore, the authors should have been aware that an increased level of cAMP from overexpressing SgrT further impairs growth on glucose.

PtsG is not "comprised of three main functional domains", as the authors state. PtsG has two functional domains (IIB and IIC) connected by a flexible linker. In the nomenclature for PTS proteins (Saier MH Jr, 1992), PtsG translates into Enzyme IICB^Glc, which is informative (and therefore should be preferred to any other designations) because it indicates a two-domain structure, a specificity for glucose, and the order of the domains (from N to C terminus).

Kosfeld A, 2012 clearly established, by cross-linking experiments, the interaction between SgrT and Enzyme IICB^Glc in the presence of glucose. They also visualized the recruitment of SgrT to the membrane by in vivo fluorescence microscopy. It is therefore unwarranted for the authors to 'hypothesize' an interaction and localization to the membrane, and to state: "Once we established that SgrT inhibits PtsG specifically and its localization to the membrane …". In addition, the demonstration by Kosfeld A, 2012, the motif KTPGRED (in the flexible linker) is the main target for SgrT, is rather convincing.

Finally, the statement "SgrT-mediated relief of inducer exclusion may allow cells experiencing glucose-phosphate stress to utilize alternative carbon sources" is inaccurate because it ignores the positive effect of cAMP on the utilization of alternative carbon sources like lactose.