XJ Autolysis™ E. Coli Strains

XJ Autolysis™ E. Coli strains are a new alternative for bacterial transformation and lysis. These strains are efficiently lysed following arabinose-induced expression of the bacteriophage λ endolysin protein, coupled to a single freeze-thaw cycle. The strains simplify protein expression and purification, and are also applicable for nucleic acid purification. They are also available with a DE3 lysogen encoding the T7 polymerase for expressing recombinant proteins driven by the T7 promoter.

		XJa Autolysis™ (E. coli, K-strain JM109)		XJb Autolysis™ (E. coli, B-strain BL21)
Cell Growth		Grows quite well, especially when media is supplemented with 1 mM magnesium.		A very robust strain, reaching higher OD's than E. coli K-strains.
Autolysis		This strain lyses very easily. Actually, the parent strain JM109 itself will release about 20% of cellular protein after one freeze-thaw cycle. This strain will lyse in a wide range of buffer conditions.		XJb lysis efficiency is 10-20 % lower than XJa. For optimal lysis, more care needs to be taken when selecting the lysis buffer. However, even very low concentrations of a detergent improve lysis significantly.
Protein Expression		Suitable for general screening, but proteases may degrade small or otherwise unstable recombinant proteins.		XJb is ideal for recombinant protein expression. It lacks Lon and OmpT proteases, leading to higher protein yields.
DNA Extraction		This strain is EndA negative and yields high quality DNA preparations.		XJb is not optimal for DNA extraction
DNA Stability		The RecA negative mutation in XJa stabilizes repetitive DNA sequences.		This strain is RecA positive.
Genotype		F`[traD36 proA+B+ laclq ∆(lacZ)M15] ∆(lac-proAB) glnV44 (supE44) e14- (McrA-) thi gyrA96 (NalR) endA1 hsdR17(rK- mK+) relA1 recA1 ΔaraB::λR, cat (CmR)		F- ompT hsdSB(rB- mB-) gal dcm ΔaraB::λR, cat (CmR)