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                         July 28, 2021

       Aiofe M. Brennen, MB,BCh,BAO,MMSc
       Chief Executive Officer
       Synlogic, Inc.
       301 Binney St., Suite 402
       Cambridge, Massachusetts 02142

                                                        Re: Synlogic, Inc.
                                                            Registration
Statement on Form S-3d
                                                            Filed July 23, 2021
                                                            File No. 333-258151

       Dear Dr. Brennen:

              This is to advise you that we have not reviewed and will not
review your registration
       statement.

               Please refer to Rules 460 and 461 regarding requests for
acceleration. We remind you
       that the company and its management are responsible for the accuracy and
adequacy of their
       disclosures, notwithstanding any review, comments, action or absence of
action by the staff.

                                                        Please contact Abby
Adams at (202) 551-6902 with any questions.




                         Sincerely,


                         Division of Corporation Finance

                         Office of Life Sciences
       cc:                                              Daniel Bagliebter, Esq.