This is a major achievement in the field of biogas research, therefore it certainly deserves publication. The first deeply sequenced metagenome and metatranscriptome databases were generated, which pave the path to a more thorough understanding of these complex microbial communities. The paper, submitted as a “data note” for GigaScience, only scratches the surface of the vast amount of information gathered in this work. The title is therefore a bit misleading as only data sets corresponding to the methanogenesis pathways are presented here, which comprise probably about 5-8% of the total sequences to be analyzed presumably in subsequent publications. Major compulsory revisions: none Minor essential revisions: change the title to inform the reader that this report is limited to the methanogenesis pathways. Discretionary revisions: none

Level of interest An article of outstanding merit and interest in its field Quality of written English Acceptable Statistical review No, the manuscript does not need to be seen by a statistician. Declaration of competing interests 'I declare that I have no competing interests' .

Authors' response to reviewers: (http://www.gigasciencejournal.com/imedia/3232474601750548_comment.pdf)