Derivative of the K12 strain with additional defects in the
expression of recA and endAI. The recA mutation leads to the
inability to homologously recombine DNA, resulting in the
stabilisation of transferred recombinant plasmids. The endAI
mutation considerably reduces endonuclease I activity, facilitating
the isolation of DNA from cells.
The gene arsR including its promoter was transferred to the DH5α
strain. The gene stems from the E. coli-specific plasmid R773 and
encodes for a transcriptional regulator with binding sites for
arsenic compounds. Furthermore, reporter genes were inserted into
the recipient organisms using a vector. These are the luxCDABE
genes required for the expression of luciferase from Photorhabdus
This system employs the pSB403-arsR plasmid in the test bacteria.
The vector background of this plasmid is the pRK415 plasmid, which
is in turn derived from the RK2 plasmid from Klebsiella aerogenes.
It contains an oriV, which enables a broad host range replication
in Gram-negative bacteria, an oriT to start the plasmid transfer
during a triparental conjugation and a tetracycline-resistance gene
cartridge. The luxCDABE genes were inserted into pRK415 and the
resulting plasmid was named pSB403. The expression of luxCDABE
genes leads to emission of light.