What is Data Storage using bacteria?

A prototype memory subsystem that uses molecules to store bits has been implemented at the Center for Molecular Electronics at the WM Keck Institute.

The molecule in question is called bacteriorhodopsin. Scientists selected it for the sequence of structural changes it makes when it reacts to light (this is called a photocycle). And that makes it an ideal medium for information storage, making it work like a bistable circuit (the famous zero and one, on and off).

The molecule initially remains in a resting state, known as bR. Through different lasers, it is made to go through a series of intermediate states until reaching a stable situation (state Q). The molecule remains this way until it is irradiated with a blue laser, at which point it returns to the bR state. Both the bR and Q states represent a binary 0 or 1, respectively. It is estimated that the information recorded on such a device would be stable for approximately 5 years.

Another important feature of bacteriorhodopsin is that the two states have vastly different absorption spectra. This makes it easy to determine the zero or one state of the molecule using a laser tuned to the appropriate frequency.

The Center for Molecular Electronics has already built a prototype memory system in which bacteriorhodopsin stores information in a three-dimensional matrix, which is built by putting the protein in a transparent cuvette filled with a gel that gives it consistency. A battery of lasers surround the cuvette, and they are used to write and read information. The lasers cut the cube into planes or pages, each one holding a set of 4096 by 4096 bits.

A similar system is used to read the data, with lower intensity red lasers. The molecules that represent the binary zeros absorb the red light, while those that are in the binary 1 state let the ray pass through them. This creates a pattern of light and dark dots on a ‘screen’ device, which captures the image as a page of binary information. To erase the data, a small pulse from a blue laser returns the molecules to a resting state.

Molecular storage garnered so much interest that three NASA Space Shuttle missions explored methods to improve the manufacturing of data cubes using microgravity.

The resulting material was more homogeneous and provided a higher storage density. It remains to be seen, however, whether the use of microgravity is cost-effective to justify a 4-fold improvement in storage capacity.

Transfer speed is initially estimated at 10MB per second similar to slow semiconductor memory. And in terms of capacity, in theory, the bucket could store up to 1 terabyte of data. Almost 1 GB has already been stored.

For now, problems with the lens system and the quality of the protein limit the system to achieve larger storage quantities. The second version of the prototype is in progress, which is expected to be used in the short term for personal computers. The design is based on proteins that are cheap to produce in quantity, and genetic engineering is even being used to increase the bacteria’s protein production.

In addition, the system has the ability to operate over a wider temperature range than semiconductors. Finally, the little cubes can be removed and gigabytes of data can be transported for storage or backup. This is possible because the cubes contain no moving parts, which is safer than using a small hard drive or cartridges.

The protein bacteriorhodopsin (bR) found in the surface membrane of halobacterium halobium absorbs light in a process analogous to photosynthesis. bR exists in two interchangeable states, absorbing blue and green light respectively, allowing information to be stored in a binary code. By arranging this product in the shape of a cube, and having a laser to access it to switch between the two states, “disks” with capacities of many Gigabytes can be obtained, for the price of 1 Giga.

The main problem is that they cannot withstand temperatures above 83 C, another drawback is that they are not very fast.

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