Synthetic Biology Parts, Devices and Applications

84 5 Functional Requirements in the Program and the Cell Chassis for Next-Generation Synthetic Biology

Illustrated in a human artifact, the master function of a printer would be to print

documents. The associated helper functions would be supplying paper, ink,

electric power, and so on. Other helper functions would correspond to the design

of the printer’s chassis. When cells are envisioned as factories, their designed

master function is production of some compounds. However this is entirely

dependent on the ability of cells to multiply while replicating both their own

program and the proper SynBio program construct, thus yoking the human con­

struct to the cell’s master function (multiplying).

While it is somewhat difficult to identify it without ambiguity, living organ­

isms appear to display two intertwined master functions. The most obvious one

is “to make a progeny.” A myriad of helper functions have evolved to allow this

master function to operate, and the huge variety of living organisms reflects this

situation. This perspective (master function/helper functions split), however,

remains fairly open. For most (this is the common view), “propagating life” is the

destination of life. However, we must consider an alternate view, where “explora­

tion” would be the master function, with “propagating life” as the immediately

downstream helper function to that particular master function. Life would thus

be a particular physicochemical process carrying further the intrinsic propensity

for exploration carried over by all entities present in the universe (following the

second law of thermodynamics that tells that physical systems will tend to

occupy as many space and energy states as they can). Here, we favored the first

choice, avoiding innovation – a major consequence of exploration – as a core

property of SynBio constructs: who would like to fly in a plane that could modify

its wings and engines in flight? We consider in what follows that the most general

goal of SynBio is to make a reproducible automaton meant to produce com­

pounds of preset design. This ranks exploration as a helper function that gener­

ally must be placed under command in SynBio constructs, and possibly even

totally inactivated. We note however that our approach is operational and not

directly linked to the concept of fitness that would entail a complementary dis­

cussion [27]. It is likely that the next decade will witness hot debates in this

domain.

Master function

Helper functions

Basic building blocks, biobricks

Construct, maintain, energize

Generation of a progeny

Metabolism of small molecules

Number of details

106

105

104

103

102

10

1 Designed production

Up / top

Bottom / down

Figure 5.1 A schematic view of functional analysis [5]. Master and helper functions are as

defined in the text.