Part:BBa_K4614203

PsrfA-sulA

This part is composed of PsrfA（BBa_k4614202）, an autoregulatory promoter derived from *Bacillus subtilis* 168 and sulA（BBa_K4614201）,which encodes SulA，an endogenous cell division inhibitor from *Escherichia coli* K12. Additionally, *PsrfA* sequence contains RBS itself, so there is no need to insert any RBS sequence during construction. CAU-China 2023 used this part to construct a cell-density-dependent expression system in *E.coli* (BL21) in our project, thus enabling engineered bacteria to express SulA without any inducer and start filamentation process automatically. We inserted this part into pJUMP46-2A vector and obtained *E.coli* BL21 harboring recombinant plasmids The recombinant strain was cultivated for over 24 hours and examined by optical microscope after stained with crystal violet. As shown in Fig.1, it is suggested that PsrfA-sulA is sufficient to cause filamentous growth of engineered bacteria. Yet，the expression characteristic of this composite part in chassis bacteria has not been qualified.

Fig.1 Division arrest by quorum - sensing induction through PsrfA of SulA. The strain used was *E.coli* BL21 that carries *sulA* gene under *PsrfA* promoter.