PONE-D-19-35806

The MsrAB Reducing Pathway of Streptococcus gordoniiis Needed for Oxidative Stress Resistance, Biofilm Formation, and Oral Colonization in Mice

PLOS ONE

Dear Dr. Lee,

Thank you for submitting your manuscript to PLOS ONE. It has been reviewed by two experts in the area. Both reviewers thought the manuscript addresses an interesting topic in oxidative stress tolerance response and biofilm formation by a major oral streptococcus, and the findings are novel. After careful consideration, we feel the manuscript is well written, but as detailed in the reviewers' comments, there are some minor issues that will require some minor modifications in order to improve the readability. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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Z. Tom Wen, PhD, DVM

Academic Editor

PLOS ONE

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Reviewers' comments:

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Reviewer #1: Yes

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: I Don't Know

Reviewer #2: Yes

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Reviewer #1: Yes

Reviewer #2: No

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Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

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Reviewer #1: The manuscript describes the MsrAB reducing pathway of Streptococcus gordonii that affects several traits of this species, especially oxidative stress response, biofilm formation in vitro, and mice oral colonization.

The experiments are elegantly designed, the text is well-written, and the figures illustrate the findings adequately. However, there are a couple of minor points that should be clarified, as follow:

- Please clarify why the terminology “oxidative stress resistance” should be used instead of “oxidative stress tolerance”.

- Line 197. Please revise the Figure citation. It appears that the correct citation would be Fig 5d and 5e, not Fig 5b.

- Lines 197-199. Please consider adding the graphs for msrA mutant in the figure.

- Lines 232-234. The following sentence is a bit awkward and should be revised: "If one reasons that these other proteins are part of a pathway involving MsrAB, then it makes sense that these mutants are also sensitive to these agents."

- Line 390: could add the pH and the composition of PBS (e.g., with or without sodium).

- Line 513: Please include the number of mice tested per experimental group for the competitive oral colonization in mice.

- Lines 531-533. Please revise the statistical analysis description because, for example, only two groups were compared (parental versus mutant strain) for mice oral colonization assay.

Reviewer #2: Authors investigate S. gordonii MsrAB gene, and elucidated its role in oxidative stress tolerance, biofilm formation and colonization in an animal model. A new pathway is proposed involving the MsrAB gene and genes in the adjacent operons. The study is very interesting based on its novelty in the context of S. gordonii. The hypothesis are tested with rigorous experiments and the data is presented clearly.

Following are some minor concerns

In the introduction, (line 51) perhaps would be better to give a little more background information about S. gordonii oral colonization and its role in dental plaque formation.

Indicate whether MsrAB gene is an extension of the MsrA gene sequence. Is MsrAB co-transcribed? Otherwise it is a bit confusing as it says that MsrA is a cytoplasmic protein and MsrAB is an extracytoplasmic protein. MsrA also seem to be sensitive to H2O2 and affects biofilm formation which are similar properties as MsrAB. Therefore it would be better to explain a bit more clearly the differences between MsrA and MsrAB.

Fig 1a – any explanation for MsrAB to have higher percentage of survival than MsrA.

Line 127- indicates data not shown. Please check with journal guidelines regarding policy for data availability.

Has the biofilm formation been tested under H2O2 and methionine sulfoxide conditions.

Please indicate the sample size of mice used for the experiment.

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Reviewer #1: No

Reviewer #2: No

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The MsrAB Reducing Pathway of Streptococcus gordoniiis Needed for Oxidative Stress Tolerance, Biofilm Formation, and Oral Colonization in Mice

PONE-D-19-35806R1

Dear Dr. Lee,

We are pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it complies with all outstanding technical requirements. Congratulations!

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With kind regards,

Z. Tom Wen, PhD, DVM

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments: