United States securities and exchange commission logo

                          September 14, 2023

       Aoife Brennan
       President, Chief Executive Officer and Director
       301 Binney Street, Suite 402
       Cambridge, MA 02142

                                                        Re: SYNLOGIC, INC.
Statement on Form S-1
                                                            Filed September 8,
                                                            File No. 333-274421

       Dear Aoife Brennan:

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

               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 Cindy
Polynice at 202-551-8707 with any questions.


                          Division of Corporation Finance

                          Office of Life Sciences
       cc:                                              Nishant M. Dharia, Esq.