While cyanobacteria are becoming increasingly attractive for various research applications, robust transcriptional and translational regulatory systems are still limited. While many systems are available for established model organisms such as E. coli, these often fail to translate directly to nonconventional model organisms.

We are currently working on different strategies to improve transcriptional control in Synechocystis sp. PCC 6803, our model cyanobacterium. Some of these strategies are also being applied in our other research areas.

(1) Inducible promoters

Chemically inducible promoters are important tools to precisely control gene expression in various applications. We recently established a vector system to test and apply different chemically inducible promoters in vivo, including both established and new systems. They were quantified in terms of dose-dependency, temporal behavior, and relative strength ^[1].

Among established systems such as rhamnose- and aTc-inducible promoters, we successfully implemented a new candidate system, the vanillate-inducible promoter, which was previously optimized for E. coli ^[2].

(2) Synthetic RNA devices

Small RNA regulators are abundant in microorganisms and are responsible for regulating the response to a number of external stimuli. In recent years, synthetic variants of these translational control systems have been designed and implemented for various applications, such as paper-based diagnostic tools ^{[3, 4]}.

As mentioned before, it remains difficult to simply transfer established systems to new organisms. We are currently investigating how redesigning established systems originally optimized for E. coli might improve their performance in Synechocystis.

Key Publications

1. A. Behle, P. Saake, A. T. Germann, D. Dienst, and I. M. Axmann, “Comparative dose–response analysis of inducible promoters in Cyanobacteria,” ACS Synthetic Biology, vol. 9, no. 4, pp. 843–855, 2020.

2. Meyer, A. J., Segall-Shapiro, T. H., Glassey, E., Zhang, J., and Voigt, C. A. (2019) Escherichia coli “Marionette” strains with 12 highly optimized small-molecule sensors. Nat. Chem. Biol. 15, 196−204.

3. Green AA, Silver PA, Collins JJ, Yin P. Toehold switches: de-novo-designed regulators of gene expression. Cell. 2014;159(4):925–939.

4. Pardee K, Green AA, Takahashi MK, Braff D, Lambert G, Lee JW, Ferrante T, Ma D, Donghia N, Fan M, Daringer NM, Bosch I, Dudley DM, O'Connor DH, Gehrke L, Collins JJ. Rapid, Low-Cost Detection of Zika Virus Using Programmable Biomolecular Components.  Cell. 2016 May 19;165(5):1255-66.