Review for 10.1186/1471-230X-9-58 (2009)

Reviewer's report
Title:The Pancreatic Zymogen Granule Membrane Protein, GP2, Binds
Escherichia coli Type 1 Fimbriae
Version: 1Date:6 April 2009
Reviewer: Carlos Balsalobre
Reviewer's report:
In this manuscript, Yu and Lowe described that the GP2 protein, a major protein
in the secretory granules of the exocrine pancreas, is a target for bacterial
binding mediated by type 1 fimbriae. The authors suggest a model by which the
GP” protein acts as a molecular decoy for bacterial adhesion, therefore
protecting the pancreas duct from bacterial colonization. The results shown are
conclusive regarding the ability of type 1 fimbriae to recognize and bind to GP2.
However, before publication several questions should be addressed.
Major concern.
-Figure 5. As the authors mentioned in the manuscript, the expression of type 1
fimbriae is under phase variation, which determine the percentage of type 1
expressing cells in the population. The percentage of expressing cells might be
different among strains under the same growth conditions. Have been
considered / studied the percentage of type 1 expressing cells in the populations
used for the studies summarize in Figure 5?
Is the percentage of type 1 expressing cells similar when comparing NU14 and
KB91 strains?
Perhaps the conclusion on the differential affinity binding of M1L and M1H is too
premature. To be corroborated will be required more accurate experiments.
Perhaps quantifying the percentage of expressing cells in each population or
using strains constitutively expressing either M1L or M1H variants- I would
suggest to delete Figure 5 and corresponding section in results or performing
new experiments to address the affinity binding of GP2 accurately.
Minor points.
-The authors highlight in the Introduction and Discussion sections the important
role of type 1 fimbriae. After reading the manuscript, the reader might get the
wrong idea that type 1 fimbriae is an exclusive virulence factor present only in
pathogenic enterobacterias. E. coli is a very versatile microorganism, highly
specialized in living interacting with mammal hosts. Most of the E. coli strains are
non-pathogenic and we (mammals) maintaina fruitful mutualism relationship with
them. Those commensal E. coli isolates are also expressing type 1 fimbriae.
Therefore, rather that to be considered as a primary virulence factor, type 1
fimbriae might be defined as a important factor for colonization of many host
niches and, therefore, that might play a key role in triggering infection by a
pathogenic isolate. A most strict definition of type 1 fimbriae and the fact that is
also present in commensally established E. coli isolates should be mentioned.
And the diversity in the pathogenicity potential of the members of the
Enterobacteriaceae family should be highlighted.
- In general, the experimental setups are poorly explained.
-The bacterial strains used are not properly described in Table1 or in the
statements under the “Bacterial strains….” section of Methods. As indicated in
the text, all strains except J96 are isogenic strains of K12 derivatives. I do not
think that the strains are isogenic and that NU14 is a K12 derivative (as recorded
NU14 is cystitis isolate, O18:K1-H7 –PMID 11740731). Strains should be
properly described in Table1. In the same way as it is indicated that AAEC072 is
a derivative of MG1655, indicate which is the parental starin of AAEC185.
- How radioactivity emission as measured by scintillation counter can be
expressed as CFU/well?
Level of interest: An article of importance in its field
Quality of written English: Acceptable
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests