Project Overview

Our project was split into 3 subprojects: AgrBDCA signal reception & Combinatorial Promoters, FsrABC/lamBCDA signal reception, and Ligand export systems.

AgrBDCA Signal Reception & Combinatorial Promoters

AgrBDCA is a quorum sensing system found to regulate virulence factors in Staphylococcus aureus. In this system, agrC and agrA function as a histidine kinase receptor and a response regulator respectively. This subproject aimed to introduce agrC and agrA in functioning form into E. coli. The circuit used for this subproject is depicted below.

Additionally, this subgroup focused on prototyping various combinatorial promoters--those which accept multiple inputs in order to determine an output state. This part of the subproject stemmed from the original overall project idea, which was to characterize a negative feedback loop with extracellular components and required a combinatorial promoter to control production of the ligand exported out of the cell. Since work had already begun on that project, it was continued, even after the shift in project design and focus, in hopes that it will later be incorporated again in the circuit.

FsrABC Signal Reception

FsrABC is another quorum sensing system homologous to the agrBCDA system of S. aureus and is also believed to regulate virulence factors involved in biofilm formation in Entereococcus faecalis. In this system, FsrC and FsrA function as histidine kinase receptor and response regulator respectively. FsrB is a membrane protein that is processed to form a cyclic 11-amino-acid polypeptide (see Ligand Export Systems).

lamBCDA is a third quorum sensing system native to Lactobacillus Plantarum that also shares homology with the agrBCDA QS system in S. aureus. Normally, it regulates adherence to surfaces and cell morphology (fact-check this). However, we are attempting to repurpose it to trigger a signal of our choice (currently just GFP fluorescence) in the "receiver" cell upon ligand release from the "transmitter" cell.

Ligand Export Systems