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Revision as of 17:42, 25 October 2012

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Bacillus Promoters

To provide a set of promoters of different strength we characterized several promoters in Bacillus subtilis. They can be divided in three different groups:

• the constitutive promoters from the Anderson collection from the Partsregistry
• the constitutive promoters P_liaG, P_veg and P_lepA from B. subtilis
• the inducible promoters P_liaI and xylR-P_xyl from B. subtilis

For the characterization of the different promoters we used the lux operon . Here, promoter activity leads to expression of the luciferase and hence light production, which can be measured as luminescence.

We also used the reporter gene lacZ . Here, promoter activation results in expression of a β-galactosidase, whose activity can be measured by breakdown of the chromophoric substrate ONPG (β-galactosidase assays). We used the reporter vector pSB_Bs1C-lacZ. See this page for an overview and background information of all evaluated promoters and see the Data page for more details.

Overview of all evaluated promoters

This section gives an overview on the strength of all evaluated promoters, which span a large range of activities. For more details and informations of the experiments see the Data page of the promoters. Note that P_veg was not evaluated with luminescence measurements and this bar is just projected from the results of the β-galactosidase assay.

Overview of promoter activity evaluated with luminescence measurements in pSBBs3C-luxABCDE. These values derive from the experiments you can find in our Data section. Lumi per OD600 are taken at a OD600 of 0.1. Values are the average and the standard deviation of three different experiments for clone 1. Shown is the activity of the Anderson promoters J23100 (#100), J23101 (#101), J23102 (#102), J23103 (#103), J23106 (#106), J23107 (#107), J23113 (#113), J23114 (#114), J23115 (#115), J23117 (#117), J23118 (#118) as well as the activity of the constitutive promoters PliaG, and PlepA. The activity of the inducible promoter PliaI is shown with (+bac) and without (-bac) induction with bacitracin (10 μg/ml). The promoter activity of Pveg is projected from the results from the β-galactosidase assay and was not measured with luminescence measurements. For the assays shown, an intermediate version of the reporter vector pSBBs3C-luxABCDE was used, which still contained one forbidden PstI site.

Evaluation of Anderson promoters in B. subtilis

The first group of promoters evaluated are the promoters of the Anderson collection ("Anderson promoters"). They have already been extensively measured in Escherichia coli where they all showed a constitutive behavior with different strength. In this project, eleven Anderson promoters were characterized in B. subtilis with the lux operon as a reporter. In B. subtilis these promoters show quiet low activity (see Data Anderson promoters ). To confirm these results some Anderson promoters were also evaluated with the reporter gene lacZ by doing β-galactosidase assays (see Data Anderson promoters ).

• J23100 (BioBrick:BBa_K823004)
• J23101 (BioBrick:BBa_K823005)
• J23102 (BioBrick:BBa_K823006)
• J23103 (BioBrick:BBa_K823007)
• J23106 (BioBrick:BBa_K823008)
• J23107 (BioBrick:BBa_K823009)
• J23113 (BioBrick:BBa_K823010)
• J23114 (BioBrick:BBa_K823011)
• J23115 (BioBrick:BBa_K823012)
• J23117 (BioBrick:BBa_K823013)
• J23118 (BioBrick:BBa_K823014)

Constitutive promoters from B. subtilis as novel BioBricks

The second group of promoters are a set of constitutive promoters from B. subtilis that we have added to the Registry. We evaluated the promoters P_liaG, P_veg and P_lepA using the lux operon as well as the lacZ gene as reporters.

• P_liaG (BioBrick:BBa_K823000)

P_liaG is a constitutive promoter from B. subtilis. It is responsible for the transcription of the last four genes of the liaIHGFSR locus and hence for the production of the components of the LiaRS system, which is important for the detection of cell wall antibiotics (Jordan et al., 2006). P_liaG was evaluated with the lux operon (see Data constitutive promoters ) as well as the lacZ (see Data constitutive promoters ) as reporter. This promoter showed a much higher activity than the Anderson promoters, but was still relatively weak in comparison to other evaluated Bacillus promoters.

• P_veg (BioBrick:BBa_K823003)

P_veg is known to show a strong constitutive activity during the vegetative growth phase and sporulation. This promoter is important for the transcription of the veg gene, which plays a role during sporulation (Fukushima et al., 2003). P_veg was only measured by using the reporter gene lacZ (see Data constitutive promoters ). This promoter was the strongest of our evaluation. It failed to clone into the lux reporter vector, presumably because of its strength.

• P_lepA (BioBrick:BBa_K823002)

P_lepA is a constitutive promoter that is important for the transcription of the bicistronic operon. One of the expressed proteins is the protein P_lepA (Homuth et al., 1996). P_lepA plays an important role during translation as it can move the mRNA-tRNA complex one step back in the ribosome which is expected to improve the fidelity of translation (Qin et al., 2006). This protein was evaluated with the lux operon as a reporter (see Data constitutive promoters ). The activity of this promoter is between the activity of the strongest Bacillus promoter P_veg and the weak P_liaG.

Inducible promoters from B. subtilis as a novel BioBrick

The last group of promoters consists of two inducible promoters from B. subtilis, P_liaI and xylR-P_xyl. They are useful if the strength and timing of gene expression needs to be tightly controlled, because these promoters need an inducer to initiate transcription. P_liaI is evaluated with the reporters lux and lacZ and added this novel promoter to the registry.

• P_liaI (BioBrick:BBa_K823001)

P_liaI is an inducible promoter from B. subtilis, which responds to antibiotics that interfere with the integrity and biosynthesis of the cell wall (Mascher et al., 2004). In the presence of a stimulus, the two-component system LiaRS is activated. The activated response regulator LiaR binds to the operator of the promoter and induces the transcription of the lia locus. When the promoter is turned on the two proteins LiaI and LiaH are expressed which play an important role in the stress response of B. subtilis. The major strength of this promoter is its very low basal activity in the absence of an inducer and its high dynamic range (Mascher et al., 2004). This promoter is evaluated with the reporter lux (see Data inducible promoters ) as well as lacZ (see Data inducible promoters ). The induction was measured with different concentrations of bacitracin, demonstrating a concentration-dependent response over a large range of promoter activities.

• xylR-P_xyl (BioBrick:BBa_K823015)

P_xyl-xylR is a xylose-inducible promoter from B. subtilis. XylR is the repressor of P_xyl in the absence of the sugar xylose. In the presence of xylose, XylR dissociates from the operator and P_xyl is active (see e.g. Kreuzer et al.). For this promoter we have not yet suceeded to clone it in a reporter vector to evaluate the activity. So far, there is no data for this promoter.