Team:HKUSTers

Our logo:The Bauhinia purpurea x variegata at the top-left corner is the floral emblem of Hong Kong; the red sundial on the left represents HKUST, as there is a large sundial in HKUST as a landmark; the Chinese brush style English letters reflect the cultural diversity of Hong Kong as a place where east meets west.

Abstract

Does God play dice with the cell?

Stochastic fluctuation in a cellular context and the lambda-phage bifurcation have been extensively studied. However, from a bottom-up synthetic aspect, we aim to exploit the cellular "noise" to build an E. coli version of a computational device, the "Random Number Generator". One random binary digit can be generated by capturing an initial Polymerase binding event with a pair of mutually exclusive promoters. Reciprocal inhibition using two repressors shall achieve unilateral expression of the "switch", with fluorescence reporters indicating the probability of each alternative occurrence. Balancing the two sets of affinity and kinetic parameters and maintaining a single copy of this synthetic device integrated into the bacterial chromosome shall improve performance.

If successful, coupled with other reporters we envision multiple extensions of this "Randomizer", including a Memorizer that utilizes a hierarchy of XOR-calculations to "store" a multi-digit random number, and intriguing pattern generation involving chemical gradients and random "population behavior". In this case, the randomizer would work like a black box. As shown in the animation below, when there is an input as start, it would generate an output, either A or B randomly.

Meanwhile, the memorizer will remember the output of randomizer, until the next randomizer output comes.

So When randomizing events happen one after another, the XOR gate reporter could integrate the neighboring two outputs from randomizer( the former one is stored in memorizer), and fires if the two outputs are different.

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• We are grateful to the generous sponsorship and support from the Lee Hysan Foundation.