Difference between revisions of "Part:BBa K4583000"

Revision as of 05:53, 5 October 2023

PYU3

PYU3 is the promoter of the gene orf-0464, and it comes from Escherichia coli. It will reach its maximum expression at the late stationary phase.

Usage and Biology

When the bacteria enter the stationary phase, the physiological state of the bacteria changes significantly. During this phase, many genes will respond to make timely adjustments. This part (BBa_K4583000) is the promoter of the gene orf-0464. Its most notable feature is that it will be expressed in the late stationary phase. Moreover, it is a self-inducible promoter, which means that no additional inducers need to be added for expression. Exogenous inducers are expensive and need to be added artificially, whereas self-induced promoters are cost-effective and relatively stable. This part is also very safe because it comes from E. coli MG1655, a commonly engineered bacterium.

• Late stationary phase promoter
• Self-inducible promoter without additional inducers
• Biosafety

There are 3 parts that have similar features characcterized by our team: BBa_K4583001(PYU7) , BBa_K4583003(PYU16), and BBa_K4583004(PYU92)

Sequence and Features

Characterization

Our characterization of this part is divided into two main parts.

• First, this promoter was placed upstream of GFP gene, forming a genetic circuit as shown in Fig. 1. This plasmid was transformed into a bacterium containing another plasmid for characterization. Green and red fluorescence were measured at fixed intervals to compare the expression time and intensity of the two.
• Second, this promoter was placed upstream of the BFP gene, forming a genetic circuit as shown in Fig. 3. This plasmid was then transferred into bacteria containing two other plasmids. Green, red and blue fluorescence were measured at fixed time intervals to compare the difference in expression time and intensity between this part and the other two parts.

For plasmid construction methods and other experimental procedures, see the Design page.

Protocols

Our experimental conditions for characterizing this part were as follows:

• E. coli MG1655
• 30^oC, 48h, under vigorous shaking
• Plasmid Backbone: PACYC
• Equipment: Multi-Detection Microplate Reader (Synergy HT, Biotek, U.S.) and Molecular Devices SpectraMax i3x.

We used GFP (excitation at 485 nm and emission at 528 nm)and BFP (excitation at 400 nm and emission at 450 nm) to characterize this part. As our focus was mainly on the expression time, we processed the obtained fluorescence data by means of the following equation: x'=(x-min)/(max-x). This treatment makes all data fall between 0 and 1, which is easier to use for comparisons between different fluorescence data (since our focus is on expression time).

Characterization using GFP in 2-plasmids bacteria

In this section we used the PACYC plasmid with PYU3 upstream of GFP gene(Fig. 1). We transformed it into L19 and L31 with PesaRwt, PesaRc, PesaRp plasmids respectively (6 combinations in total) and characterized them using 24-well plates. The characterization results are shown in Fig. 2

As can be seen from the characterization results, with the exception of three combinations (L19-PesaRp-PYU3, L31-PesaRc-PYU3, and L31-PesaRp-PYU3) the expression time of this element is significantly different from that of the other element in terms of time and intensity.

In the case of the combination L19-PesaRwt-PYU3, for example, the expression of the other part peaked at about 12 h, whereas the expression of this part peaked at about 38 h. The expression of the other part peaked at about 12 h, whereas the expression of this part peaked at about 38 h.

Characterization using BFP in 3-plasmids bacteria

In this section, we used the PACYC plasmid with PYU3 upstream of the BFP gene (Fig. 3). Based on the results of the last Characterization, we transformed it into L19 and L31 with PesaRwt, PesaRc, PesaRp plasmids and PesaS plasmid respectively (4 combinations in total) and characterized them using 24-well plates. The characterization results are shown in Fig. 4.

From the characterization results, we can see that there is a significant delay in the expression of this part from the other promoters. From the characterization results, we can see that there is a significant delay in the expression of this part from the other promoters. For this characterization, we used a Molecular Devices SpectraMax i3x, which has a much higher precision. In addition, the difference between the 2-plasmids system and the 3-plasmids system may also account for the difference.

Reference

[1] Talukder, A A et al. “RpoS-dependent regulation of genes expressed at late stationary phase in Escherichia coli.” FEBS letters vol. 386,2-3 (1996): 177-80. doi:10.1016/0014-5793(96)00426-7