Seres Therapeutics (MCRB) SC 13D Seres Therapeutics, Inc.

Exhibit 1

JOINT FILING AGREEMENT

The persons below hereby agree that the Schedule 13D to which this agreement is attached as an exhibit, as well as all future amendments to such Schedule 13D, shall be filed jointly on behalf of each of them. This agreement is intended to satisfy the requirements ofRule 13d-1(k)(1)(iii) under the Securities Exchange Act of 1934.

Dated: June 28, 2019

FLAGSHIP VENTURELABS IV, LLC
By:	Flagship Ventures Fund IV, L.P.
By:	Flagship Ventures Fund IV General Partner LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager
FLAGSHIP VENTURES FUND IV, L.P.
By:	Flagship Ventures Fund IV General Partner LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager
FLAGSHIP VENTURES FUNDIV-Rx, L.P.
By:	Flagship Ventures Fund IV General Partner LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager
FLAGSHIP VENTURES FUND IV GENERAL PARTNER LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager
NUTRITIONAL HEALTH LTP FUND, L.P.
By:	Nutritional Health LTP Fund General Partner LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager
NUTRITIONAL HEALTH LTP FUND GENERAL PARTNER LLC
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	Manager

FLAGSHIP PIONEERING FUND VI, L.P.
By:	Flagship Pioneering Fund VI General Partner LLC
By:	Flagship Pioneering, Inc.
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	CEO
FLAGSHIP PIONEERING FUND VI GENERAL PARTNER LLC
By:	Flagship Pioneering, Inc.
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	CEO
FLAGSHIP PIONEERING, INC.
By:	/s/ Noubar B. Afeyan, Ph.D.
Name:	Noubar B. Afeyan, Ph.D.
Title:	CEO
/s/ Noubar B. Afeyan, Ph.D.
NOUBAR B. AFEYAN, PH.D.
/s/ Edwin M. Kania, Jr.
EDWIN M. KANIA, JR.