Microbial Communities in Underground Gas Reservoirs Offer Promising Biotechnological Potential

Round 1

Reviewer 1 Report

* Revise abstract and write more interestingly.
* Keywords: Capitalize only the first keyword and use semicolon between the keywords.
* Novelty of the work should be justified.
* Could you please add a practical or future perspective of the study somewhere in the last part of the introduction?
* The experimental design is easy to understand.
* The part of analytical methods should be provided more detail.
* The statistical analysis can be more attractive.
* Kindly improve on the discussion. What is the significance of the results of the work? Include more relevant literature.
* There are some space mistakes. I would suggest authors to check the manuscript carefully and correct them manually.
* It is suggested to cite references within 5 years of research to maintain the reliability of results obtained.
* Please make sure abstract and conclusion word count follows the set guidelines of journal.
* It is suggested to add one comparative table with already published literature with the present study.
* Please send the paper for English correction to avoid minor typos and grammatical error.
* In figures font are not readable. High resolution images to be submitted.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

In the presented article microbial syntrophy between bacteria and methanogenic archaea was found and confirmed in three natural Underground gas storages. The species composition of the microbial community, which has methanogenic activity and increases the yield of methane, has been studied. The article is written in a language sufficient for understanding and contains few errors. In general, the article contains data for the development of a promising direction of biomethanation, which allows to reduce the use of fossil carbon. Minor typos to correct are listed below. On the content, there are three small remarks:

1. 358, 527: Newly proposed phillum, genera, taxa, etc. should be cited so readers can become familiar with new information. The article where the fillum name „Hadesarchaeaeota“ was suggested should be cited. Also citation should be added here:  "recently proposed taxa Candidatus Methanomethylicus and Candidatus Methanofastidiosum." 

2. In section Discussion [440-442] the purpose of the study is stated: "The objective of the quantitative analysis of methanogens was ..." However, there are no sufficient data presented on the dynamics of methanogens during the year. Perhaps this goal should be reformulated or removed from the topic. It may be better to confine the authors to a brief conclusion based on limited data.

3. In the Discussion, in continuation of the introduction, it is necessary to clearly indicate which types of methanogenesis were identified in representatives of each geographical sampling site.

Minor typos to correct:

98: carboxyl group that is oxidized

101: which catalyzes in the oxidation

130: "volume of 0.75"  specify L or mL

218:  was mixed

222-226: It is not clear what the difference was between reaction conditions during the first five cycles and the followed 30 cycles.

251: database [26] was performed

286: respect <relative> to calcite

291: and are approach

297: Was it minus 225 mV: "... redox potential of <->225 mV..."

315:  Possibly it should be better to designate as C-D plot or dC – dD

358, 527: Newly proposed phillum, genera, taxa, etc. should be cited so readers can become familiar with new information. The article where the fillum name „Hadesarchaeaeota“ was suggested should be cited. Also citation should be added here:  "recently proposed taxa Candidatus Methanomethylicus and Candidatus Methanofastidiosum."

486: was confirmed in all but one of the sampled wells except one.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf