Role of the Mn-Catalase in Aerobic Growth of Lactobacillus plantarum ATCC 14431

Round 1

Reviewer 1 Report

The present manuscript deals with the importance of Mn-catalase in the aerobic metabolism of Lactobacaillus plantarum ATCC 14431. The authors have shown that the absence of this catalase causes a significant inability of the bacterium to survive in an aerobic environment and this effect was more pronounced in the presence of hydrogen peroxide as a typical representative of reactive oxygen species. The approximately three-fold increase in the concentration of manganese ions compared to the basic growth medium at least partially reversed the ability of the bacterium to grow in the presence of oxygen, which the authors explain by the protective properties of manganese against the ROS due to its chemical properties. Another significant effect was observed at the morphological level of the bacteria. As the authors correctly concluded, the absence of protective properties of catalase in the mutant most likely causes a significant increase in ROS, which then damages the molecules of which the cytoplasmic membrane is formed. This action can subsequently be reflected in the resulting deformation of the bacterial shape. Overall, it can be said that the work brings some new knowledge in the field of research. The conclusions reached are supported by appropriately selected and implemented experiments.

From the reviewer's point of view, I have only one problem that the authors should solve. The specific growth rate is given in the text without the deviation calculated by the authors from the two biological replicates, as stated in the materials and methods. Firstly, it would be appropriate to include the deviation in the text (XXX ± S.E.M.). Second, the authors should try to calculate the specific growth rate by a nonlinear regression method using a suitable growth model (for example Gompertz). As the experimental growth curves are almost exemplary, this should not be a problem. If the values ​​obtained in this way do not differ from the values ​​calculated from the linear regression, then let the authors keep these values ​​in the text. Otherwise, it is necessary to use the results obtained from the growth model. Similarly, the statistical deviation should be reported in the text for catalase activity as well as in the methods for how many repetitions were this deviation calculated.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Abstract

Please, do indicate importance of Lactobacillus plantarum ATCC 14431: its use, route of contact with humans, population it is of the importance to.

Introduction

The essence, why to investigate Lactobacillus plantarum ATCC 14431 has not being pointed out. It shoud be the leading permission, the primary information. Is only for the theoretical scientific study or the bacteria has some role in the microbiome of humans.

It is not clear on the scope of the public health why should we care of H2=2 and other species formed in Lactobacillus plantarum ATCC 14431. Does inhibition of their presence in the bacteria affect humans?

Results

Figure 1. Letters on the gel images are not readable. The comment on the image should be readable and the adjunction to the gel 2 (white-black) should be explained.

Overall, the footnote of the Figure 1 is barely comprehensible, and should be written by using more words and more precision.

Figure 2. It should be visually improved, legends of both axes to be of the same size and type, The title of the Chart is no needed since it is explained in the footnote. What do the barres stand for: standard error or deviation?

Acronyms (abbreviations) for all enzymes in the Table 1 should be listed.

How the weak positive reaction (b) is defined. What indicator has been used to distinguish it from the negative reaction?

Why the CAT activity is lined by bolded lines?

Figure 3. Either axis title is not possible to be red.

Figure 4 is mentioned in the Discussion but it has not been presented in the manuscript.

Conclusions

I greet the given conclusions. But without the authors having write them down, I would not be able to reach them from the results and their discussion. Please start from the conclusion and rephrase the Results and Discussion To be clearly understandable what is the reasoning lying behind them.

„Under aerobic conditions, MnKat is essential for normal aerobic growth of L. planta-rum ATCC 14431; it is required for removing endogenous H2O2.“ – The result which indicates it. Besides, the sam should be stated when presenting the corresponding result in the Results.

„Inactivation of MnKat results in hyper-sensitivity to added H2O2.“ – it should be indicated in the Results that lead to this conclusion.

„Medium containing high [Mn] (e.g., APT) improves the growth of the MnKat mutant strain (NC1543) relative to that seen in the low [Mn] medium (e.g., MRS).“  In the results indicating it the same statement should be presented.

Author Response

Please see attachment

Author Response File: Author Response.docx