Electrochemical Control of Biofilm Formation and Approaches to Biofilm Removal

Round 1

Reviewer 1 Report

The review contains three parts; in the first, the authors give an overview of biofilm as a microorganism’s phenotype; in the second, the authors count methods that are in use in biofilm study and in the third, the most interesting one, the authors describe the involvement of electrochemistry in the biofilm studies.

The text is simple and easy to read; I think readers can quickly understand what the authors want to say. Although the three parts are not very well connected, this does not interfere with reading the text. I think the third part is the most intriguing, and probably the value of this review is there.

Some points or suggestions for discussion. It is pretty common for biofilm scientists to separate adhesion into two steps: reversible and irreversible (lines 67-70 and 214-221). However, it seems to be an attachment to the surface, one process that should be described as the first stage of biofilm, especially when the formation of microcolony and mature biofilm are combined in one stage.

Chapter 3, please give more information about the food contamination by biofilms. How much food is wasted due to biofilm? At least approximately. In the current version, the emphasis is on food spoilage, but the focus should be on food spoilage due to biofilm.

Lines 111-114, where the authors count the factors influencing biofilm formation. Please mention metals (for instance, Cu, Mg, Ag) here, which you discuss in the following chapters.

Lines 133-135, This part is unnecessary; it has already been written.

Lines 158-175, It is unnecessary to mention all known techniques just as a list. It would be more beneficial for readers to classify techniques by the principle of the methods.

Lines 251-255, How similar are biofilm formation conditions and life in host organisms? Does virulence mean good biofilm formation ability? It may be wise to give readers a hint of the conditions under which biofilm studies were performed in vitro.

Line 458-459, Shewanellaceae is a family, and Proteobacteria is a phylum. Please write correctly.

Line 458, I think Geobacter was meant instead of Beobacter.

Line 468, Please give some examples of endogenous redox mediators used among bacteria.

Author Response

Good evening dear Reviewer 1,

First of all, we thank you for your comments and suggestions that help to improve our review paper. All changes are marked by yellow colour in revised version. You are right that the three main chapters are not well connected to be the whole concept of the review paper more understandable for potential readers. For this reason, our contribution had to be extended. Below, you can find your comments with the appropriate responses.

a) Some points or suggestions for discussion. It is pretty common for biofilm scientists to separate adhesion into two steps: reversible and irreversible (lines 67-70 and 214-221). However, it seems to be an attachment to the surface, one process that should be described as the first stage of biofilm, especially when the formation of microcolony and mature biofilm are combined in one stage.

It is true that the first stage of biofilm formation includes two steps, namely reversible and also irreversible adhesion of planktonic cells. Now, the description of biofilm formation phases is correct in the text.

b) Chapter 3, please give more information about the food contamination by biofilms. How much food is wasted due to biofilm? At least approximately. In the current version, the emphasis is on food spoilage, but the focus should be on food spoilage due to biofilm.

Unfortunately, it has to be noted that the term “food contamination by biofilms” is not correct. In practice, if it is found that the food is contaminated, whole food processing equipment will be rehabilitated without finding out the causes. For this reason, it is difficult to monitor them and make any statistic. Nevertheless, we tried to found at least some information [Ref. 90-93] regarding your queries and include them at the end of the introduction of Chapter 3.

c) Lines 111-114, where the authors count the factors influencing biofilm formation. Please mention metals (for instance, Cu, Mg, Ag) here, which you discuss in the following chapters.

Thanks to your suggestive comment, a completely new Chapter 2.2.1 Effect of Metal Ions on Biofilm Formation has been created to demonstrate the possibility of using electrochemical methods in real-time monitoring of some metal ions that have a major impact on biofilm formation.

d) Lines 133-135, This part is unnecessary; it has already been written.

These lines were deleted based on your correct comments.

e) Lines 158-175, It is unnecessary to mention all known techniques just as a list. It would be more beneficial for readers to classify techniques by the principle of the methods.

The classification of all techniques developed for characterisation of biofilms including their principles was not the aim of this review. Moreover, some review papers dealing on this topic have been already published (see Ref. 81). Contributors (co-authors) to Chapter 2 are convinced that the classification in the form of the scheme in Figure 1 is sufficient. We believe that potential readers can easily find in the relevant references what they interest.

e) Lines 251-255, How similar are biofilm formation conditions and life in host organisms? Does virulence mean good biofilm formation ability? It may be wise to give readers a hint of the conditions under which biofilm studies were performed in vitro.

It cannot be simply said that virulence plays a substantial role in biofilm formation. It depends on other factors (see lines 300-304).

f) Line 458-459, Shewanellaceae is a family, and Proteobacteria is a phylum. Please write correctly.

We thank you for this comment. You are right. This mistake was corrected in the text.

g) Line 458, I think Geobacter was meant instead of Beobacter.

This typos error was corrected.

h) Line 468, Please give some examples of endogenous redox mediators used among bacteria.

Three examples of endogenous redox mediators were mentioned.

We believe that you will be satisfied with our responses and changes that had to be done in the manuscript.

With the best regards!

Dr. Milan Sýs

Reviewer 2 Report

1. The author should introduce the background of the review and why it is necessary to write a review of the topic in the Introduction.
2. I think Section2 and Section3 can be integrated. If the author wants to emphasize the importance of biofilms in food, then the author should change the focus of this paper (revise the title).
3. In Section5 the author should also add perspectives on this topic.

Author Response

Good evening dear Reviewer 2,

all co-authors thank you and are grateful for your factual comments and suggestions that help to improve our contribution to be more attractive for potential readers. The background of the review was introduced and we believe that individual chapters are now more interconnected. Below, your comments with our responses are shown.

a) I think Section 2 and Section 3 can be integrated. If the author wants to emphasize the importance of biofilms in food, then the author should change the focus of this paper (revise the title).

The aim of this review paper was to show the public what electrochemistry offers in control of biofilm formation and its removal from conductive surfaces. As stated in the literature, biofilm infections constitute a number of clinical challenges that attract the interest of many scientific disciplines. However, biofilms in food processing still represents unexplored area of research, and yet so important.

The whole article is intentionally divided into three main sections (Chapters 2, 3, and 4), for better reader’s orientation. Section 2 and 3 belongs rightly to our contribution, so that readers can compare the current methodology in biofilm monitoring and removal with rather alternative electrochemical approaches.

b) In Section5 the author should also add perspectives on this topic.

The Section 5 (Conclusion) was extended and additionally enriched by some perspectives on the present topic.

Now, we believe that the present review article is sufficiently improved.

With the best regards!

Dr. Milan Sýs