Basic

Composite

Description

BBa_R0040 This part was used as a negative control for fluorescence measurements, since it is non-coding except for chloramphenicol resistance.
BBa_K1352000 – Ag43 under pBAD/araC promoter. This part codes with the Ag43 pro-protein under the control of the pBAD/araC regulation system.
Briefly, Antigen 43 (Ag43) is a bacterial cell adhesion outer membrane protein, belonging to the auto-transporter family. It consists of two subunits – β, a trans-membrane β-barrel protein and α, a secretory protein that non-covalently binds to the β subunit and is responsible for the aggregation by forming α-α dimers. These two subunits come from the same peptide chain that is cleaved by an aspartate protease domain in the same pro-protein. Phenotypically, Ag43 expression leads to inter-cell aggregation. We used BBa_K1352000 as PCR templates to make tagged variants of Ag43 (BBa_K2168000 and BBa_K2168001). For a excellent description of Ag43, we recommend visiting .
BBa_I746908 – sfGFP under pBAD/araC promoter. This part codes for sfGFP under regulation of pBAD/araC system. We used this part to characterize the pBAD/araC regulation system, more specifically promoter activity repression by glucose, since this had paradoxically not been checked in the past 12 years. For more details about experiments and results, please click .
BBa_K1072000 – Lux based quorum sensing system.
Quorum sensing systems are biological regulation circuits that allow gene regulation dependent on local cell-densities. A well-studied example is that in Aliivibrio fischeri lux quorum sensing system.
The system works as follows. luxI gene under the pLuxI promoter encodes for the LuxI AHL-synthetase enzyme that synthesizes AHL, non-polar signalling molecules that can diffuse out into the extracellular environment. Another protein encoded by this part, LuxR from the luxR gene under the pluxR promoter, binds to AHL and the LuxR-AHL complex homodimerizes further to give a (LuxR-AHL) dimer. This dimer acts as a transcriptional activator for the pluxI promoter, leading to a positive feedback loop for luxI-luxR expression and AHL synthesis.
Further, the dimerization of the LuxR-AHL complex leads to a positive Hill coefficient for the process leading to a switch-like behaviour with respect to the AHL concentration. This lead to a switch like behaviour with respect to cell-density since the AHL production rate is dependent on the local cell density.
Hence, any gene under the pluxI promoter would show a switching behaviour dependent on cell-density. We decided to check the same for BBa_K1072000, one for the few parts that has a complete quorum sensing system with a fluorescent reporter. So far, the characterization of this part has a microscopy image of green fluorescent cells; however, quorum sensing can established only by a growth curve. We have shown quorum sensing by this part experimentally. For experimental details, please click .
BBa_K525998 – This part consists of a T7 bacteriophage promoter followed by a very strong RBS – BBa_B0034. This part was chosen by us for collaborating with the on their . The activity of this promoter seems to be inconclusive

Ag43 measurement systems