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Question 1#
> Prior to our study, other investigators have shown that pooled animal fecal samples from mice can be successfully transplanted into GF recipients (Rawls JF et al. Cell 2006). As the published literature describing protocols on the transplantation of human stool into GF mice is limited and generation of GF mice is a costly procedure, we directly chose to perform the FMT experimentation based on the procedures described by Koren et al (Koren O Cell 2012).
> In our study, 63-69 different mice recieved FMT from 5 donor material( n = 63/depressive group; n = 69/control group). Equal quantity of fecal samples from each donor was pooled. Here, we need to assess the three kinds of depression-like behaviors in these mice. Larger samples were always used to narrow the statistical deviation. Maybe this procedure was not completely perfect. The potential limitation was clearly prestented in manuscript: It should be noted that this procedure may not completely capture the entire composition of the microbial community. As the reviewer’s suggests, further FMT studies using multiple independent pooled samples from different donors or individual samples from different donors would be of great value in addressing which experimental method(s) can more effectively capture the key characteristic gut microbiota in MDD patients in order to identify the specific gut microbiotic species that disproportionally contribute to the development of depression.
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> Question 2#
> In this work, Prof. Julio Licinio had a major contribution in the design of the experiments and preparation of the manuscript. In the author contributions section, Julio Licinio's name was erroneously printed as "JY”. We regret not having caught that typographical error earlier. Note that Professor Licinio visited Prof Xie in China several months before submission and extensively discussed the direction of this research project. Profs Xie and Licinio have been in close contact since then. Moreover, Prof Peng Xie has the highest (most senior) academic appointment at SAHMRI (Prof Licinio’s home institution), where Prof Xie is Senior Principal Research Fellow. Only a handful of appointments are made at SAHMRI at this level, and only when there is full, ongoing collaboration. Prof Xie’s appointment at SAHMRI reflects the extensive and close contact between Profs Licinio and Xie. See this ref for confirmation of the appointment: Cipriani A, Zhou X, Del Giovane C, Hetrick SE, Qin B, Whittington C, Coghill D, Zhang Y, Hazell P, Leucht S, Cuijpers P, Pu J, Cohen D, Ravindran AV, Liu Y, Michael KD, Yang L, Liu L, Xie P. Comparative efficacy and tolerability of antidepressants for major depressive disorder in children and adolescents: a network meta-analysis. Lancet. 2016 Aug 27;388(10047):881-890. Note that others at Prof Licinio’s institution also gave input into the work, including Prof Ma-Li Wong. Prof Licinio was the only contributor from SAHMRI listed as author, because we felt that he was the only one whose contributions were essential to the project, exceeding our high threshold for co-authorship. Given Prof. Licinio’s in-depth understanding of the topic, and of these specific experiments and datasets, including his input to the experimental design, along with his invaluable contribution to the manuscript, we believe that it was fully justified to list him as a co-corresponding senior author. Note that we have discussed other work of our group with Prof Licinio, but because his contribution was not so fundamental, we did not include him as a co-author in our those other papers.