Chromium-Driven Changes in Heavy Metal Resistance Genes During Pig Manure Composting

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript currently uses author-date citations within the text, but according to the journal’s guidelines, all references should be cited using numerical format (e.g., [1], [2]) rather than by author names. Please revise the in-text citations accordingly to ensure compliance with the journal’s required referencing style.

The authors have implicitly indicated the research gap and novelty regarding the influence of chromium and antibiotic residues on MRG dynamics during composting. However, I recommend that the manuscript explicitly articulate the research gap and clearly highlight the novelty of the study in the Introduction. Specifically, it would strengthen the manuscript to clearly state what aspects previous studies have not addressed and how this work advances the current understanding. This clarification will better contextualize the significance and contribution of the study for readers.

In the introduction, antibiotics and their potential interactions with chromium and MRGs are mentioned, but these aspects are not further addressed or analyzed in the results and discussion sections. To improve clarity and coherence, it would be helpful to either remove the references to antibiotics from the introduction or include relevant data and discussion on their effects throughout the manuscript. This adjustment will ensure that the scope of the study is clearly defined and the narrative remains consistent

I noticed a minor typo in the conclusion L 470 (“omposting” instead of “composting”). Additionally, it might strengthen the conclusion to briefly mention the practical implications or potential applications of these findings for composting practices or environmental management.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The paper entitled "Chromium-Driven Changes in Heavy Metal Resistance Genes During Pig Manure Composting" addresses an interesting and significant issue: the effect of Cr on the composting process of pig manure, particularly in terms of the interplay between MRGs, microbial composition, and physicochemical attributes. While the issue considered in the article is specific, the methods described can be used for larger-scale studies, albeit with minor transformations. The authors used well-proven analysis methods that have been described previously, so the reliability of the results obtained should not be in doubt. I believe that the article can be published in Fermentation, after the following issues will be addressed.

1. During the study, the authors added pyridine carboxylate chromium to the control samples to simulate the chromium content. However, the experimental part lacks data on how the degree of chromium oxidation was controlled throughout the experiment. This issue is of fundamental importance for the expected result.
2. The authors do not mention the formula or CAS number of the chromium complex used anywhere in the text. However, if the chromium compound is bis(pyridine-2,6-dicarboxylate) chromate, then the chromium is in oxidation state +3. This makes it unclear where the +6 chromium came from (lines 320 onwards).
3. Chromium can exist in several oxidation states simultaneously, including +3, +6, −4, −2, −1, 0, +1, +2, +4 and +5. The chromium atom's oxidation state can change depending on the conditions. Why did the authors choose pyridine carboxylate chromium as the model compound, rather than another salt?
4. The authors note that the control samples were placed in foam boxes. Could the material of the container have affected the results of the analyses?
5. The font used in all five figures is barely visible, even at high magnification. Therefore, rather than simplifying the reading of the paper, the content of the illustrations complicates it. Please note that the font size used in the figures should match that used in the main part of the paper.
6. In the caption to Fig. 2, the letters a, b, c and d should be deciphered.

Author Response

Please see the attachment.

Author Response File: Author Response.docx