Beware of metaphors: chasses and orthogonality in synthetic biology

Every descriptive language is not only metaphoric and interpretative, but it is also developed (or adopted) ad hoc to fulfill a certain agenda. Even the hardcore scientific languages of mathematics and physics are not entirely neutral--let alone the much softer terminology of biology. We use metaphors all the time in science and that is useful as long as they serve their purpose well and we are aware of them. But it is a serious mistake to identify uncritically the thing and the metaphors employed to bring the thing to mind. I address here two of the most sparkling metaphors brought about by synthetic biology: chassis and orthogonality--the first borrowed instance from engineering of vehicles, and the second from computer terminology (itself borrowed from mathematics). For the sake of simplicity the discussion is limited to the connotation of these two concepts in the prokaryotic realm. The power of such metaphors from describing the state of affairs in synthetic biology and for setting a vigorous research and technology schedule is analyzed. Awareness of the meta-languages and allegories that are being adopted by the SB community should help to frame other controversial concepts such as artificial cells or synthetic life.