Revision as of 04:43, 30 October 2008

Bacillus subtilis

Introduction

B. subtilis swimming in LB medium

Bacillus subtilis is a commonly used laboratory bacterium. It is often considered the gram-positive E.coli beacuse of the amount of use it has recieved and the amount of knowledge there is about the organism.

Its genome has been sequenced (as has the genome of at least one strain - 168) and it has been used at iGEM since 2007. It is gradually coming in to favour - particularly in the UK - as a potnetial host for many synthetic systems and devices, often due to the characteristics that make it different to e.coli.

The lack of parts for B. subtilis on the registry have reduced the common use of B. subtilis as a chassis, but with the increased use of B. subtilis, particularly by iGEM teams, it may be soon become a third major host for the registry.

Benefits vs Challenges

	Advantages	Disadvantages
	Protein Expression
	Single Membrane - B. subtilis is a gram-positive bacterium and contains only a single membrane. This makes B. subtilis an ideal chassis for secretion of organic molecules.	Peptidase activity - B. subtilis express both intracellular and extracellular exopeptidases and so there is a risk that expressed proteins may be cleaved up inside the cytoplasm or in the solution.
	Enginnering B. subtilis
	Availability of Potential Parts - B. subtilis is a highly studied organism, with a fully sequenced genome. As a result, B. subtilis provides many useful potential parts.	B. subtilis parts - Although many labs and iGEM teams have looked at B. subtilis as a potential chassis, there are relatively few working B. subtilis parts available in the Registry. This however is rapidly changing and soon there will be the basic parts required to make B. subtilis a highly viable chassis.
	BioBrick Assembly
	Natural Competency and Integration - B. subtilis has been noted for its ease and efficieny of transformation. In addition, integration of exogenous DNA into the chromosome has been well studied and provides an alternative to using traditional plasmids.	Vector Degradation - B. subtilis does not use all the same vectors as E. coli. One reason for this is that B. subtilis often recognises vectors grown in E. coli as foreign and digests them. Vectors and shuttle vectors are thus not reliable carriers of genetic information.
	Chassis Properties
	Sporulation: Transport - Under stress conditions, B. subtilis will form spores. These spores are highly resistant versions of single cells, able to withstand extreme temperatures and pH. These spores are capable of growing into new cells once favourable growing conditions are restored. Due to the resistance of spores, there is a great potential for manipulating them for transporting B. subtilis devices and constructs.	Sporulation - Under stress conditions, B. subtilis will form spores. These spores are highly resistant versions of single cells. While B. subtilis itself isn't pathogenic, its spores can be damaging if inhaled. They are also highly resistant to many conditions that are used to kill cells.
	High Motility - B.subtilis is often referred to as a highly motile organism in comparison to other bacterium.
	Non-pathogenicity - B. subtilis is a non-pathogenic organism that is commonly found in soil. As a result, B. subtilis has a biological harzardous level of 1 and offers a useful non-pathogenic chassis for synthetic biologists.

Commonly used strains

168

Bacillus subtilis strain 168 is one of the most commonly used in the laboratory and its specific genome has been sequenced.

168 tends to be the traditional gram-positive lab worhhorse.

It was used by the Imperial 2008 iGEM team in the project Biofabricator subtilis and proved to be a useful and reliable chassis, being easy to transform, highly motile and generally easy to work with.

This chassis currently provides the basis for the B. subtilis chassis characterisation data

Py79

Like 168, Py79 is also a lab strain of bacillus subtilis.

It is commonly used in research and also is a general workhorse strain.