Ingested Microplastics Can Act as Microbial Vectors of Ichthyofauna

Round 1

Reviewer 1 Report

The topic of the article is interesting, the methods used make it possible to obtain useful information about the process being studied, but the article contains incorrect expressions, and the text of the article requires additional careful editing.

                  Comments

1.      Latin is written in Italic: Aeromonas

2.      Expression “microplastic is a bacterial vector” is wrong. It is possible to say “Microplastics could serve as a vector for the transport of the bacteria”, “Microplastics are vectors for bacteria”.

3.      The same comment for “Microplastics Act as Microbial Vectors”,  “Microplastics can act as vectors”.

4.      “the adherent strains”. Wrong expression. Strain could be adhered, only cells of certain strain.

5.      “polymer analysis of the excreted samples was performed, which shown no signs of degradation” – showed.

6.      “Microplastics pollution has become ubiquitous, so much so that these particles are now being unintentionally assimilated by both animals [1,2] and humans”. Microplastics could be accumulated in bodies of animal or human, but not assimilated.

7.      «fewer scientific releases reported MPs potential as microbial carriers». There are a lot of research devoted to this topic.

8.      “The most frequent MPs pollution occurs in the aquatic environment, due to anthropogenic factors”. Why? What factors did you mean?

9.      “and even in regard to a potential biodegradation through digestion and intestinal microbiota” – Correct, please.

10.   “to remove non-adherent microbiota”. Please correct.

11.   “associated microbiota” Please, correct.

12.   in various different type of other polymers [34,48,49].   types

13.   nor has its complete excretion took place in the first day   -  taken

14.   References must be formatted in the same style in accordance with the requirements of the journal.

It’s a pity that the authors do not pay attention to a recently published review on a related topic:  Stabnikova, O.; Stabnikov, V.; Marinin, A.; Klavins, M.; Klavins, L.; Vaseashta, A. (2021). Microbial life on the surface of microplastics in natural waters. Applied Sciences (Switzerland), 11, 11692. https://doi.org/10.3390/app112411692.

Minor editing of English language required

Author Response

Please see attached

Author Response File: Author Response.pdf

Reviewer 2 Report

The idea at the heart of the study is a very good one. The ability of microplastics to act as a vector for microbiota transfer when ingested and excreted by living organisms and further released into the aquatic environment is very poorly documented and such papers are interesting.

However, the quality of writing, data presentation and discussion leaves much to be desired. Therefore, the manuscript should be substantially improved before publication. Specific comments and suggestions are provided below.

Title: My guess is that it should be "Ingested microplastics act as microbial vectors FOR ichthyofauna".

Introduction:

1.  “Nylon” is the trade name given to a group of aliphatic polyamides. So in a scientific paper this should be mentioned and certain type of PA used for the experiments indicated.

2.  «Predatory fish species in particular present higher MPs accumulation compared to omnivorous species, as Sequeira et al. [20] reported” – controversial statement, many other papers have refuted it. It is necessary to cite data from more recent reviews of MP uptake by freshwater fish published after 2020, or to remove this paragraph altogether as it is not relevant to the topic of the study.

3.  Please italicise the Latin genus name in "...fish pathogens such as Aeromonas have a particularly high affinity...".

Material and Methods:

1.    Section 2.1. The maintenance of the fish and the conduct of the experiment should be described in more detail. For example, it is not stated what food was used, at what intervals were the fish fed? With such a description of the methodology, the study would be impossible to repeat.

2.    Section 2.2. Please indicate the composition of the Amies media or, if commercial, the manufacturer). The same applies to other media mentioned such as Chapman agar, 5% blood agar, bile aesculin agar, Salmonella-Shigella agar, Mac Conkey sorbitol agar, DCL agar, Yersinina agar and xylose-lysine-deoxycholate agar.

3.    Section 2.3. Please explain in more detail how mass spectrometry can be used for the taxonomic identification of microorganisms. And provide references to previous publications using this method.

4.    Section describing data analysis, QA/QC procedures and statistical methods is missing.

Results:

1.    This paragraph needs to be reworded: “These results show that the largest numbers of nylon strips were excreted by fish after 48 and 72 hours after ingestion (not statistically significant, p-value = 0.643 >> 0.05). The number slightly decreases after 96 hours, but still not significantly different from the numbers at 48 and 72 hours (p-value of ~0. 158 >> 0.05). Lower numbers of strips were recovered at 24, 120 and at 148 hours. The number of strips excreted at 24 hours and 120 hours are similar (not statistically significant, p-value = ~ 0.444 >> 0.05)”. As no significant difference was observed in the number of MPs exctreted at 48, 72, 96 h, you cannot use the terms "larger" and "lower". Also indicate whether the number of MPs at 24, 120 and 148 h and at 48, 72 and 96 h was statistically different to explain the data presented in Figure 1.

2.    Figure 1. What variation is shown in a bar graph with mean values? Standard deviation or error of the mean?

3.    Section 3.2. Please expand the section. Present the results as a compact table or figure in the main text. These are the most important data according to the aim of the study, they should be systematised and illustrated.

4.    Section 3.2. If you repeat the species name in the text, you can use only a capital letter to indicate the genus (e.g. A. hydrophila).

5.    Section 3.2. You mentioned "initial innoculation" (correct - "inoculation") here, but this manipulation was not described in the "Materials and methods" section.

 Discussion

1. Use abbreviated genus names of bacteria in the third paragraph: A. hydrophila, A. jandaei, etc.

2.    What about the number of bacteria detected? Were they different for the same species in the control and experimental samples? And compared to the initial inoculation?

3. The discussion section should be expanded. At the moment it is just a series of statements without any real discussion – reasons, consequences of the observed phenomena, without sufficient comparison with published data. 

Unfortunately, the manuscript does not contain line numbering, which makes it difficult to review.  Please provide line numbers after revision.

English needs revision.

Author Response

Dear reviewer,

Please see attached our point-by-point replies.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have done a good job. The paper is now suitable for publication.