This year, team RDFZ-China is dedicated to developing a novel, safe, and precisely controlled postoperative colorectal cancer therapy based on engineered probiotics.

Our project, RectomeDy FotoZymogen, integrates genetic modules for tumor targeting, light-inducible control, dual therapeutic payloads, and biological safety.

To realize this system, we contributed 8 new basic parts and 1 regulatory Signalling module, each experimentally validated or logically constructed to advance synthetic biology approaches in probiotic therapeutics.

BBa	Part Name	Type	Length(bp)	Designed by
BBa_256O7C4S	coa	basic-Coding	1410	qianyu chen
BBa_25PXJQ2S	INP-HlpA	basic-Coding	813	xunwen xiao
BBa_25GADZ5E	YopE1-15-PD-L1	basic-Coding	507	xunwen xiao
BBa_25LPRH4Z	BphO	basic-Coding	591	xunwen xiao
BBa_25IOLYVT	PadC4	basic-Coding	2037	qianyu chen
BBa_25J2E9TK	MrkH	basic-Coding	705	qianyu chen
BBa_250LF4YU	YhjH	basic-Coding	768	qianyu chen
BBa_K1096002	mazF	basic-Coding	657	Jiayi Chen
BBa_259UHA9L	NETMAP red light-induced gene expression	basic-Signalling	4902	qianyu chen

Basic Parts

BBa_256O7C4S (coa, 1410 bp) – Encodes coagulase (Coa), a pro-thrombotic enzyme designed to locally block tumor blood supply. In our system, its expression is tightly regulated by a red-light induction circuit, ensuring precise activation only within illuminated tumor regions.

BBa_25PXJQ2S (INP-HlpA, 813 bp) – A surface display fusion protein combining Ice Nucleation Protein (INP) and HlpA, enabling our engineered E. coli Nissle 1917 to specifically adhere to colorectal cancer cells via HSPG recognition, ensuring high targeting precision.

BBa_25GADZ5E (YopE1-15-PD-L1, 507 bp) – Encodes a PD-L1 nanobody fused with a secretion tag (YopE1-15), allowing effective extracellular delivery. This enables local immune checkpoint blockade, restoring anti-tumor immunity within the colorectal microenvironment.

BBa_25LPRH4Z (BphO, 591 bp) – Encodes ferredoxin oxidoreductase BphO, an essential red-light chromophore synthesis enzyme required for the NETMAP optogenetic system. This part ensures stable intracellular chromophore supply for light sensing.

BBa_25IOLYVT (PadC4, 2037 bp) – Encodes the red-light sensor protein PadC, the key photoreceptor component of the NETMAP system. It enables external, non-invasive optical regulation of therapeutic gene expression.

BBa_25J2E9TK (MrkH, 705 bp) – Encodes the transcriptional activator MrkH, which participates in our modular logic control loop, strengthening dynamic regulation of expression and ensuring system robustness.

BBa_250LF4YU (YhjH, 768 bp) – Encodes YhjH, a phosphodiesterase that regulates intracellular c-di-GMP levels. It functions as a signal amplifier for tumor-environment sensing and enhances bacterial motility control.

BBa_K1096002 (mazF, 657 bp) – A well-established toxin component of the mazEF system, employed in our project as a key module of the three-layer biosafety kill switch, ensuring complete bacterial self-elimination after therapy.

BBa_259UHA9L (NETMAP Red-Light-Induced Signalling, 4902 bp) – A modular, red-light-inducible Signalling and sensor network, enabling external optical control of target gene expression. This system forms the central regulatory core of RectomeDy FotoZymogen, integrating therapeutic activation, timing precision, and safety assurance in a single, tunable design.

Our contribution extends beyond this year’s therapeutic system — it establishes a complete optogenetic control and tumor-targeting toolkit for probiotic applications:

1、A Modular Red-Light Control System:

The NETMAP Signalling and chromophore-related genes (PadC, BphO) provide future teams with a ready-to-use framework for optical gene regulation in E. coli. These can be easily adapted for biosensors, controlled secretion systems, or dynamic biomanufacturing.

2、A Validated Tumor-Targeting Display System:

The INP-HlpA fusion part offers a robust and reusable targeting mechanism for binding HSPG-overexpressing cells — valuable for future cancer-targeted probiotic or drug-delivery designs.

3、A Safe Dual-Function Therapeutic Toolkit:

The Coa and PD-L1 nanobody parts demonstrate a synergistic approach combining vascular blockade and immune activation. These modules can inspire future iGEM teams to design multifunctional, multi-mechanism therapeutic bacteria.

4、An Enhanced Biocontainment Framework:

By integrating mazF with multi-level control logic, we provide a validated, biosafety-compliant suicide switch framework — a vital reference for any future teams seeking to meet iGEM’s safety standards.

In summary, the RectomeDy FotoZymogen parts collectively form a safe, modular, and reproducible system that embodies the engineering spirit of synthetic biology and contributes reusable, well-documented tools to the iGEM community — fully aligned with iGEM’s principle of “Getting, Giving, and Sharing.”