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Coding sequence for TnaA in E. coli

Description

Indigo is one of the oldest and most useful dyes in the world and is widely used in various areas including food and drug industries. Once before the production of indigo was greatly relied on the extraction of these pigments from plants. Although chemical synthesis of indigo was invented in the 18th century, the method still had lots of drawbacks that it can cause pollution and the substrates for synthesis were harmful to people's health.

With the development of synthetic biology, as early as 1993, pathways of indigo synthesis were found in some bacterias such as Methylophilus and Acinetobacter and various genes including FMO and sty gene group were discovered useful for bacteria indigo synthesis(Hack Sun Choi. et. al. 2003, Gui Hwan Hana.et. al. 2010). In order to achieve our goal of producing natural and harmless hair dyes by engineered bacteria, iGEM20_Shanghai_SFLS_SPBS built the basic part of TnaA, which is adopted from the composite BioBrick of 2019 Team GreatBay_SZ.

The TnaA gene codes for tryptophanase in E.coli, which helps convert L-tryptophan, the common amino acid, into indole and is common in the metabolic pathway of tryptophan in E.coli. The product indole is the initial substrate for the synthesis of indigo. Subsequently, The FMO gene that is originally found in M. aminisulfidivorans is responsible for converting indole that is produced by tryptophanase into indoxyl. Finally the product indoxyl will be converted into indigo in the presence of oxygen. The TnaA gene in the biobrick is successfully expressed in E.coli DH5α in the experiment of iGEM20_Shanghai_SFLS_SPBS, and indigo is successfully produced in the presence of L-tryptophan and oxygen.

Experiments & Results

Successful production in E. coli DH5α

We decided to try producing indigo in E. coli DH5α, the bacterial strain used by iGEM19_GreatBay_SZ. Surprisingly, the tubes showed blue color. We then used shake flasks and E. coli DH5α to produce indigo. We added 100 mg/L L-Tryptophan in one shake flask and no substrate in another. Both shake flasks successfully produced indigo, and the one with the substrate produced more pigments than the other. The production in the flask with substrate is estimated to be 41.6 g/L.

Sequence & Features