Memo-Cell project

Introduction

Humans have invented many ways to count, from very simple manual counters to more complex logic gates implemented within electrical circuits.

Counting is an essential process in our daily life, and implementing an automated counter into bacteria could have many applications, from medical to industrial.

Counting with single-cells is a concept that has already been tackled but which is still in its infancy. Some counters have already been designed and implemented, but could only count up to three; though they could be extended. However, as these systems rely on the number of different transcription factors / recombination enzymes available AND characterised, extension to achieve counting more that 3 is pretty limited. Moreover, it is important to notice that for these designs, once an element has been used for counting, it can not be reused.

The Memo-cell project is a novel and original approach to free from these constraints, allowing a limitless counting.

The framework for this approach is fairly simple. We will implement memory in the bacteria using a sequential integration of DNA pieces into the bacteria chromosome, controlled in space and time.
Memory will then be hardcoded in the genome by the number of DNA pieces integrated one after another in the genome.
Our plan is to create a mechanism that allows the bacteria to integrate in its chromosome a specific piece of DNA at a specific location, every time it detects a specific input signal. The successive detection of signals will results in the successive integration of DNA pieces one after the other on the chromosome. The total number of DNA pieces integrated on the chromosome will then correspond to the number of times the signal has been detected.
For instance, we could integrate the light sensing module developed by the *** igem team and plug it to our memo-cell module. Hence, the memo-cell module would be triggered when there is light, and our bacteria will count the number of days.



To achieve this goal, we had to hijack and to extensively engineer three mechanisms:

• 1. The recombination system of Phages Lambda and HK022;
• 2. The recombination system of Transposon Tn916;
• 3. The microcin C51 from a specific E.coli strain.