Difference between revisions of "Part:BBa K322921"

Revision as of 14:01, 9 October 2022

B. subtilis levansucrase. Lethal to E. coli in presence of sucrose.

sacB encodes the Bacillus subtilis levansucrase, which catalyses hydrolysis of sucrose and synthesis of levans (high molecular weight fructose polymers). It is lethal to gram-negative bacteria E-coli.

It works with cat as an alternative method for inserting BioBricks into the genome by using homologous recombination rather than restriction digestion. SacB is used as a negative selection marker, which allows to insert genes onto the chromosomes without leaving a selection marker. The method can thus be reused indefinitely.

The protocol for BRIDGE can be found on the Edinburgh 2010 igem wiki.

http://2010.igem.org/Team:Edinburgh/Project/Protocol

Measurement of SacB promoter:

SacB promoter is the starting sequence of part BBa K322921. It is separately documented as BBa_K2224001 [1] by SMS_Shenzhen team in 2017.

We, SMS_Shenzhen Team, tested the strength of this promoter by comparing it with J23100. According to our measurement,SacB promoter is a functional promoter in E.coli expression system.

For detailed information about SacB promoter, please see the ‘measurement’subtitle on page [2].

Sequence and Features

Contribution: iGEM22_WHU-China

This is a sucrose lethal gene that encodes the enzyme levosucrase, which catalyzes the production of high molecular weight fructose polymers called Levans. Given that heterologous expression of SacB is lethal in the presence of sucrose in many Gram-negative bacteria, SacB is widely used as a genetic engineering tool.

In our project of directed evolution , we added SacB in our constructed vector as a counter-selection element , and we collected some related information from the past papers to verify our experiment.

Fig.1 SacB addition in our constructed vector , which serves as a counter-selection element.

Fig.2 In the process of counter-selection,we add sucrose on the surface of solid culture medium . (A): No colonies are found on the medium supplemented with sucrose;(B):There are many colonies on the medium without added sucrose.

Reference:
[1] Ambrosis N, Fernández J, Sisti F. Counter-Selection Method for Markerless Allelic Exchange in Bordetella bronchiseptica Based on sacB Gene From Bacillus subtilis. Curr Protoc Microbiol. 2020 Dec;59(1):e125.
[2] Chen W, Li Y, Wu G, Zhao L, Lu L, Wang P, Zhou J, Cao C, Li S. Simple and efficient genome recombineering using kil counter-selection in Escherichia coli. J Biotechnol. 2019 Mar 20;294:58-66.
[3] Logue CA, Peak IR, Beacham IR. Facile construction of unmarked deletion mutants in Burkholderia pseudomallei using sacB counter-selection in sucrose-resistant and sucrose-sensitive isolates. J Microbiol Methods. 2009 Mar;76(3):320-3.
[4] Tan Y, Xu D, Li Y, Wang X. Construction of a novel sacB-based system for marker-free gene deletion in Corynebacterium glutamicum. Plasmid. 2012 Jan;67(1):44-52.