Team:Groningen/Project/Construct

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Constructs

An amyE intergrational backbone

To transform B. subtilis with our developed biobricks we have improved the amyE intergrational backbone from Munich's iGEM team 2012 (BBa_K823023) that had no inducible promoter. We've added the HyperSpank IPTG inducible promoter from Rudner's Lab 2004. This promoter is placed right in front of the prefix, so any biobrick can be inserted in this backbone (BBa_K1085014) and can be induced with IPTG.

In figure 1 a close-up of the promoter is shown.

The HyperSpank promoter has a single nucleotide change (G->T) at the -1 position. This increases the expression levels but also causes leaky expression when IPTG is absence[1]. To improve repression, a second lacO operator site has been inserted 71 bp upstream of the first. (David Rudner, Harvard Medical School)

Figure 1: The HyperSpank promoter with in orange the lacO operators, in red the -35, -10, +1 signals and in green the prefix.

Figure 2: BBa_K1085014 with: The amp gene for ampicillin resistance in E. coli; The cat gene for chloramphenicol resistance in B. subtilis; The HyperSpank promoter with its repressor lacI; The amyE up- and downstream fragments for intergration in the amyE locus.

Promoter activity

BBa_K1085014 was constructed with two variants of GFP (one form our group and one from the biobrick system, BBa_E0840). BBa_K1085014-GFPmg and BBa_K1085014-BBa_E0840 were transformed to B. subtilis. Overnight cultivated strains were diluted 1:100 in fresh medium and grown till OD~0.45 and induced with 1mM IPTG. A 1,2 and 3 hour sample was analysed under the microscope, results are shown in figure 3.
Figure 3
A:
B:
C:
Figure 3: In (a) An overlay picture is shown from the phase-contrast and GFP-channel picture. In (b,c) the intensity in of ~40 cells in the GFP-channel, were analyzed from two pictures. The average intensity (AU) from the cells are plotted above with the standard deviation. In (b) a GFP from our group is shown and in (c)a biobricked GFP (BBa_E0840) is shown in a plot. wt=wildtype, T0= before induction, T1,2,3=#h of induction with IPTG.





Bacillus subtilis silk genes collection derived from Argiope aurantia MaSp2

One of the challenges that the project includes is the production of spider silk. In order to achieve this goal iGEM Groningen designed for you what we call “The Bacillus subtilis silk assembly shop”.
The 'shop' idea follows those conceptual steps:

  1. Design your own silk protein
  2. Browse the iGEM Groningen silk subunits collection:
    3. Spider silk
    subunit    		 Biobrick id Construct Features
    RBS Strep-tag Stop codon
    E1 BBa_K1085000 25px 25px
    BBa_K1085001 25px
    E2 BBa_K1085002
    BBa_K1085003 25px
    Tail BBa_K1085008 25px
    BBa_K1085009 25px 25px
    table 1: table description.
  3. Select the subunits you need
  4. Assemble them together
At this point the silk product is ready to be produced (See production backbone) and employed for the desired purpose.

The Groningen team enriched the iGEM database adding several new Bacillus subtilis BioBricks containing spider silk gene subunits. This provides the iGEM community with a new bunch of parts; which, in the future, will help anyone in assembling its own silk protein and customize it with different features.
It is the first time that silk-coding BioBricks suitable for Bacillus subtilis are introduced into the database. Therefore this work marks the starting point for further studies about silk within the Bacillus subtilis chassis inside the iGEM framework.

The advantages shown by our collection are mainly two which can be summarized as follows:

  1. Less cloning steps The iGEM database provides a lot of basic parts which can be employed for the development of the desired synthetic machine, however, the assembling protocols are often tedious and time consuming. For this reason all the silk subunits, produced by the Groningen team, have been created in different versions. The aim of such a design enables the end-user to reach quicker the desired silk protein without bothering too much about the molecular issues.
  2. Compatibility with BioBrick standards We are aware that the BioBrick assembly standard is the foundation of the iGEM method, allowing all different laboratories to build on each others work. That is why the silk subunits are compatible with the following standard:
    • BBF RFC 10
    • BBF RFC 12
    • BBF RFC 21
    • BBF RFC 23
    • BBF RFC 25
    • BBF RFC 1000
We divided the several silk coding sequences in 3 big groups:
  • Subunit E1
  • Subunit E2
  • Tail
subunit E1, subunit E2 and Tail. Each of them has been produced and stored into the iGEM submission backbone (pSB1C3). Each of them shows certain features: signal sequences, strep-tag and Ribosome Binding Site (RBS).

The aim of the molecular genetic design is to create a handy toolbox in order to produce any desired combination of silk-like genes which can be expressed in Bacillus subtilis for several purposes. Everything is designed within the RFC[23] standard framework. This enables the user to join together all the different parts creating in-frame fusion silk-like proteins.

The following parts have been produced, sequenced and are available into the standard BioBrick submission backbone (pSB1C3):


What kind of spider silk gene is it
What are general problems with this gene
Where did we get it from.
Codon optimisation, solved the problems.

Strep-tag


Why this is needed
For what purposes it comes in handy

Signal peptide


Why is it so important.
The use of existing pathway so not lots of trouble
The signal sequences are nice addition to the registry
how the pathway works and how the silk will be secreted

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