Human Practices: Overview

Overview

This year, we tried to jump into as many chances as possible to learn more about role and value of synthetic biology and the future of this academic field. In this new information society, we can easily obtain knowledge on the Internet and many iGEMers may think the learning happens only in the labs or on the computers. That's sometimes true, but it's not always true that a bunch of information automatically comes to our pocket, which means we sometimes have to break free from the obsession with the project work.

We can proudly say our integrated human practices helped us make progress in our project design. By integrating our human practices with the results from our wet lab experiments and modeling, iGEM2017 Team TokyoTech have executed our project with improved design in accordance with comments from general public, and have strengthened the public engagement of a two-way dialogue between our team and the public through this summer.

Basic Human Practices

1) Organizing a symposium about synthetic biology for the public

On Oct 1st, we held an open symposium for middle school and high school students. We planned and managed the event and as guests, we invited three experts from microbiology (Prof. Oshima), synthetic biology (Prof. Kiga) and bioethics (Dr. Nudeshima).

2) Giving lectures about biosafety at local high schools

On September 2nd, we visited two high schools in Saitama Prefecture. We gave lectures and organized groupwork activities at both schools.

3) Attending Summer School (Theme: Social Epidemiology)

On September 9th and 10th, some team members attended 5th Summer School of Japan Society of Research and Information on Public and Co-operative Economy. (The venue was Ritsumeikan University in Kyoto.)

Integrated Human Practices

Applications

1) Coli watch

Cph1 of cyanobacteria is a transmembrane protein and has histidine kinase activity as AHK4 does. Histidine kinase activity of Cph1 is activated upon light exposure. If a chimera protein of Cph1 and AHK4 (Cph1-AHK4) is constructed and expressed in E. coli, this protein will work as a novel photoreceptor. The Cph1-AHK4 chimera protein will induce transcription from the cps operon in response to light exposure.
Taken together, when the Ptet-traI, Ptet-cph1/AHK4, and Pcps-rfp gene cassettes are introduced to E. coli, the cells change color depending on light.
By wearing the above mentioned E. coli cells on our wrist skin cells, we can see the color change according to the intensity of the light.We named this light sensible E. coli “Coli watch.”

2) Therapy

Recently, we have found many studies on gene therapies and Drug Delivery System (DDS) to anaerobic solid cancer. These treatments were carried out using the anaerobic bacteria harboring anti-cancer drug genes. However, there are two problems for these treatments; (i) it is difficult to transduce genes to specific human cells, (ii) the effect of the anti-cancer bacteria is not permanent, because the anti-cancer bacteria lose niches by killing cancer cells. When the cancer recurs, re-administration of the anti-cancer bacteria is needed. Such repeated treatments involve pain and economic burden as well as putting patients in danger. Thus, through introducing the following genes, anti-cancer E. coli is expected to stay at a least concentration for a long period.
(i) introducing the chimeric transcription factor (relA-traR) and the iP synthesis enzymes (atIPT4, log1) to human cells.
(ii) introducing Ptet-traI, Ptet-AHK4, and Pcps-mazF to E. coli cells.
(iii) introducing a sensor protein gene to detect cancer cell-specific metabolites to E. coli cells. Concerning the above point (iii), one preceding study implies the existence of such metabolites that attract bacteria [1]. As a consequence, the E. coli cells promptly respond to cancerous recurrence. Therefore, patients will be released from the anxiety of recurrence or frequent checkup, improving the patients’ QOL. For not only cancer but also other diseases that easily recurrence, similar therapeutic E. coli can be settled for prompt and repeated healing. Our co-cultivation technology seems to give a new possibility of medical treatment and of living with diseases. The detailed mechanisms are described below (Fig. 3).

Step1 Introduce the gene of the chimeric transcription factor (relA/traR, constitutive expression) and iP synthesis genes (atIPT4 and log1, inducible expression).
Step2 Administer the E. coli cells harboring the following three genes; the anti-cancer genes, the C8 synthase gene (traI), and the iP receptor gene (ahk4).
Step3 The E. coli cells that are grown at a central part of anaerobic solid cancer and kill the cancer.
Step4 As the cancer cells are killed, the transduced human cells sense the increased number of E. coli cells.
Step5 Transduced human cells produce and secrete iP as an E. coli proliferation inhibitor.
Step6 Suppress the excessive growth of E. coli.
Step7 If the cancer recurs, the E. coli cells detect cancer-specific metabolites, move to the cancer, and resume growing to increase their niche.
Step8 The E. coli cells kill the cancer again, and the transduced human cells inhibit the excessive growth of E. coli cells. The cell concentration balance between human and E. coli cells is sustained.

Co-culture with bacteria and Immune system When human and bacterial cells are allowed to co-existed artificially, negative influence of bacteria on human health is concerned and whether the bacteria are killed by the human immune system is unclear. However, in this system, we do not aim to introduce bacteria inside human cells but aimed extracellular co-existence. Therefore, it is considered that:
- Human and bacterial cells co-exist only extracellularly and the influence of the immune system is not needed to consider.
- If bacteria excessively grow, the growth will be suppressed by the proliferation inhibition system.
- If bacteria get too close to human cells like invading human cells, human cells sense it and an immune reaction occurs. However, this immune reaction is too weak to lead extermination of bacteria.

Fig. 3 Model of cancer therapy by co-existnce with anti-cancer bacteria

3) Photosynthesis

We human beings are heterotrophs, and it has long been a dream to make energy ourselves through photosynthesis. In recent years, some studies have been carried out in which genetically modified cyanobacteria are co-cultured with human cardiomyocytes to build a complete heart. These co-cultures aim to supply sufficient oxygen from cyanobacteria to all human cells, even when forming a three-dimensional structure [2].

In other words, if we could co-exist with photosynthetic bacteria, we could obtain energy by ourselves as well as constructing organs in three dimensions. In addition, if livestock animals and photosynthetic bacteria could co-exist, the feed cost could be reduced drastically.

However, in the above scheme, generation of reactive oxygen species (ROS) is inevitable, and the human cells are damaged by ROS. If photosynthetic bacteria co-exist in animals that originally do not possess photosynthetic functions, a mechanism to suppress photosynthesis is necessary. Therefore, by incorporating the co-culture system we established to the above scheme, it is expected that overgrowth and photosynthesis of photosynthetic bacteria and generation of ROS can be suppressed.

Reference

[1]Potential role of intratumor bacteria in mediating tumor resistance to the chemotherapeutic drug gemcitabine (2017) Science 15 Sep 2017: Vol. 357, Issue 6356, pp. 1156-1160