On 2015 Jul 03, Martine Crasnier-Mednansky commented:

Gene identification number VC1822 and VCA1045 relate to PTS proteins with A, B, and C domain (not just an A domain as inferred from the text). In accordance with the 'Proposed Uniform Nomenclature' for the PTS proteins Saier MH Jr, 1992, gene VC1822 encodes an Enzyme IIACB^N/D and VCA1045 an Enzyme IICBA^Mtl . It would be a great benefit for PTS researchers if the nomenclature was used beyond for example Escherichia coli.

Based on figure 6A, the authors report the CRP-cAMP complex negatively regulates the expression of tcpA in the absence of the PTS. However, because figure 6A shows there is no significant difference in expression between the cya and the cya ptsH mutant strain or the crp and the crp ptsI mutant strain, and no significant difference in expression between the wild type and the crp or cya mutant strain, it could be concluded from figure 6A that the CRP-cAMP complex does not play a major role in the transcription of tcpA in the TCP-producing AKI medium used by the authors. This conclusion is not supported by previous data indicating CRP-cAMP indirectly regulates negatively the expression of tcpA by inhibiting the transcription of tcpPH (Kovacikova G, 2001). However the cAMP level varies in response to changes in carbon and energy sources. Thus, if the level of cAMP is relatively low in the AKI medium as compared to LB medium, production of TcpA occurs. This provides an explanation for the present observation indicating deletion of crp does not significantly affect production of TcpA (figure 6A). It also provides an explanation why incorporation of a crp mutation in the El Tor strain C6706 allows production of TCP in LB medium (Skorupski K, 1997).

Figure 6B does not indicate that "…in the EI or Hpr mutants, intracellular cAMP concentrations were significantly higher than that in wt cells" - as stated. In fact, intracellular cAMP concentrations are significantly higher in the cpdA mutant strains, possibly indicating a role for cAMP phosphodiesterase in regulating the cAMP levels.

On 2015 Jul 03, Martine Crasnier-Mednansky commented:

Gene identification number VC1822 and VCA1045 relate to PTS proteins with A, B, and C domain (not just an A domain as inferred from the text). In accordance with the 'Proposed Uniform Nomenclature' for the PTS proteins Saier MH Jr, 1992, gene VC1822 encodes an Enzyme IIACB^N/D and VCA1045 an Enzyme IICBA^Mtl . It would be a great benefit for PTS researchers if the nomenclature was used beyond for example Escherichia coli.

Based on figure 6A, the authors report the CRP-cAMP complex negatively regulates the expression of tcpA in the absence of the PTS. However, because figure 6A shows there is no significant difference in expression between the cya and the cya ptsH mutant strain or the crp and the crp ptsI mutant strain, and no significant difference in expression between the wild type and the crp or cya mutant strain, it could be concluded from figure 6A that the CRP-cAMP complex does not play a major role in the transcription of tcpA in the TCP-producing AKI medium used by the authors. This conclusion is not supported by previous data indicating CRP-cAMP indirectly regulates negatively the expression of tcpA by inhibiting the transcription of tcpPH (Kovacikova G, 2001). However the cAMP level varies in response to changes in carbon and energy sources. Thus, if the level of cAMP is relatively low in the AKI medium as compared to LB medium, production of TcpA occurs. This provides an explanation for the present observation indicating deletion of crp does not significantly affect production of TcpA (figure 6A). It also provides an explanation why incorporation of a crp mutation in the El Tor strain C6706 allows production of TCP in LB medium (Skorupski K, 1997).

Figure 6B does not indicate that "…in the EI or Hpr mutants, intracellular cAMP concentrations were significantly higher than that in wt cells" - as stated. In fact, intracellular cAMP concentrations are significantly higher in the cpdA mutant strains, possibly indicating a role for cAMP phosphodiesterase in regulating the cAMP levels.