Team:Technion Israel/Description

Imagine if you could direct bacterial populations towards a specific location.
This ability could have amazing applications, such as research, bioremediation, substance detection and much more!

S.Tar

FlashLab

Project S.Tar aims to provide the iGEM community with the ability to control bacterial chemotaxis. Furthermore, we designed the FlashLab chip as an application of our system for the purpose of detection. We hope that future teams and researchers find it useful and put it to good use exploiting all of its potential.

Nature provides a tremendous toolbox

Bacteria are able to sense the external environment, and move in response to a chemical stimulus (Fig. 1). This phenomenon is called chemotaxis.

The bacteria sense their surroundings using receptor proteins (chemoreceptors). These are transmembrane proteins, that contain a periplasmic ligand binding domain (sensing region) and a conservative cytoplasmic domain (signaling region).

A detailed explanation on the chemotaxis system can be found here.

The variety of chemoreceptors existing in nature is limited, and most of them comprise of relatively the same structure. The main difference being their ligand binding domains.

Fig. 1: Scheme of chemotaxis concept.

Fig. 2: Chemoreceptor structure illustration.

S.Tar – control of chemotaxis

Project Super Tar - S.Tar in short, is designed to be a novel broadband platform for controlled chemotaxis. Our project focuses on expanding the repertoire of chemoreceptors found in nature. The base of our project is the E. coli Tar chemoreceptor or more specifically, its ligand binding domain (LBD).
We show that by mutating the native Tar LBD (2) or by interchanging it with that of other receptors (3), the E. coli chemotaxis system can be programmed to respond to completely new ligands.

Fig. 3: S.Tar project - Programming the chemoreceptors to respond to new ligands by modifying the ligand binding domain.

We were successful in generating two new functional chemoreceptors:
1. PctA-Tar , a chimera created by replacing the Tar LBD with that of the Pseudomonas receptor PctA.
2. Histamine-Tar, a receptor constructed with the help of computational design - using the 'Rosetta' bioinformatics software suite to design mutations in the Tar receptor. Using S.Tar, scientists will be able to control the movement of bacteria, and direct them towards or away from a target material.

FlashLab – A S.Tar detector

As an application of our system, we have designed FlashLab - a user friendly fluidic chip, which utilizes the high sensitivity of the chemotactic response. FlashLab is a simple and low cost platform for the detection of any chemoeffector, using S.Tar bacteria.

Fig. 4: Flash Lab - our designed detection chip.

References:
1. Bi, S. and Lai, L., 2015. Bacterial chemoreceptors and chemoeffectors. Cellular and Molecular Life Sciences, 72(4), pp.691-708.

2. Moretti, R., Bender, B.J., Allison, B. and Meiler, J., 2016. Rosetta and the Design of Ligand Binding Sites. Computational Design of Ligand Binding Proteins, pp.47-62.

3. Reyes‐Darias, J.A., Yang, Y., Sourjik, V. and Krell, T., 2015. Correlation between signal input and output in PctA and PctB amino acid chemoreceptor of Pseudomonas aeruginosa. Molecular microbiology, 96(3), pp.513-525.

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