Standards not that standard

Abstract

There is a general assent on the key role of standards in Synthetic Biology. In two consecutive letters to this journal, suggestions on the assembly methods for the Registry of standard biological parts have been described. We fully agree with those authors on the need of a more flexible building strategy and we highlight in the present work two major functional challenges standardization efforts have to deal with: the need of both universal and orthogonal behaviors. We provide experimental data that clearly indicate that such engineering requirements should not be taken for granted in Synthetic Biology.

Keywords: Biobrick parts; Orthogonality; Standardization; Synthetic biology.

Fig. 1

Behaviour of a set of Biobrick parts in different E. coli host strains. The output of DNA constructs consisting of a promoter coupled to a reporter protein was measured under the same experimental conditions for each strain. Note that both constitutive and inducible promoters were tested, and different reporters (fluorescence proteins and coloured compounds) were used. All measurements were normalized by the OD600 value of each culture, and corrected by the basal output observed in control strains transformed with an empty plasmid. Error bars show the standard deviation of three independent biological replica. See Additional file 1 for further experimental details

Fig. 2

Orthogonality tests performed on a simple combination of two Biobrick parts. a Fluorescence output displayed by E. coli XL1 strain transformed with a single plasmid containing a constitutive promoter coupled to a green fluorescent protein (Bb1), a single plasmid containing the same promoter coupled to a red fluorescent protein (Bb2), and a combination of both plasmids. Plots showing flow cytometry measurements performed on individual cells (dots). b Comparison of the proteomic profile of an E. coli strain constitutively expressing a green fluorescent protein (green lines) with that of the same strain carrying an empty plasmid (red lines) and the control non-transformed strain (blue lines). Proteins showing a statistically significant change in expression are numbered according to Additional file 1: Table S2