BioBrick

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BioBrick standard biological parts are DNA sequences of defined structure and function; they share a common interface and are designed to be composed and incorporated into living cells such as E. coli to construct new biological systems. BioBricks represent an effort to introduce engineering principles into synthetic biology.

BioBricks were introduced by Tom Knight at MIT.^[1] Drew Endy^[2], also at MIT, and Christopher Voigt, at UCSF, are also heavily involved in the project. A registry of several hundred public domain BioBricks is maintained by Endy's team at http://parts.mit.edu. The annual iGEM competition promotes the BioBrick concept by involving undergraduate and graduate students in the design of biological systems. The term BioBrick, intended to be used as an adjective, is a trademark of the not-for-profit BioBricks Foundation.

One of the goals of the project is to provide a workable approach to nanotechnology employing biological organisms. Another, more longterm goal is to produce a synthetic living organism from standard parts that are completely understood.^[3]

Each BioBrick is a DNA sequence held in a circular plasmid; the "payload" of the BioBrick is flanked by universal and precisely defined upstream and downstream sequences which are technically not considered part of the BioBrick. These sequences contain restriction sites for four restriction enzymes, which allows for the simple creation of larger BioBricks by chaining together smaller ones in any desired order. To facilitate this assembly process, the BioBrick itself may not contain any of these restriction sites.^[1]

There are three types of BioBricks: "parts", "devices" and "systems".^[2] "Parts" are the building blocks and encode basic biological functions (such as encoding a certain protein, or providing a promoter to let RNA polymerase bind and initiate transcription of downstream sequences); "devices" are collections of parts that implement some human-defined function (such as producing a fluorescent protein whenever the environment contains a certain chemical); "systems" perform high-level tasks (such as oscillating between two colors at a predefined frequency).

Example BioBrick systems honored at previous iGEM competitions include:

E. coli detector for arsenic that responds with pH change;
E. coli producer of various scents such as banana or mint;
human cell line engineered to inhibit excessive response to Toll-like receptor activation, so as to avoid sepsis.

Two measures for the performance of biological parts have been defined by Drew Endy's team: PoPS or Polymerase per second, the number of times a RNA polymerase passes by a certain DNA point per second; and RiPS or Ribosomal initiations per second, the number of times a ribosome passes a certain point on mRNA each second.^[4]