Zymo Research - XJ Autolysis™ E. coli Strains

DESCRIPTION

The use of XJ Autolysis™ E. coli strains offers a new alternative to current methods for bacterial transformation and bacterial cell lysis. XJ Autolysis™ E. coli strains are efficiently lysed following arabinose induced expression of the bacteriophage lambda lysozyme (i.e., endolysin) protein coupled to a single freeze-thaw cycle. Lysis is quick, reproducible, and simpler compared to current lysis methods. XJ Autolysis™ E. coli strains are suitable to accomodate processing of multiple samples as well as scaling up to larger sampling volumes.

Zymo Research offers a range of chemically competent strains of E. coli having transformation efficiencies >10⁸ transformants/µg pUC19 DNA. With the needs of the researcher in mind, the scientists at Zymo Research developed a unique method to make E. coli stains chemically competent and avoid the requirement of heat-shocking and related procedures. This dramatically reduces processing time, and, in most instances the entire procedure is complete in 10-20 minutes bypassing the need for a lengthy outgrowth period. For transformation, simply mix DNA with competent cells, incubate on ice 10-20 minutes, and spread onto a selection plate.

The use of XJ Autolysis™ E. coli strains offers a new alternative to current methods for bacterial transformation and bacterial cell lysis. XJ Autolysis™ E. coli strains are efficiently lysed following arabinose induced expression of the bacteriophage lambda lysozyme (i.e., endolysin) protein coupled to a single freeze-thaw cycle. Lysis is quick, reproducible, and simpler compared to current lysis methods. XJ Autolysis™ E. coli strains are suitable to accomodate processing of multiple samples as well as scaling up to larger sampling volumes.

	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.
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 compared to XJa. To achieve optimal lysis, more care needs to be taken when selecting lysis buffer. However, even very low concentrations of a detergent improve lysis significantly.
Protein Expression	Suitable for general screening, but proteases may degrade the recombinant proteins, especially small or otherwise unstable proteins.	Higher protein yields are usually obtained using this strain. XJb is also deficient in both Lon and OmpT proteases, making it especially suitable for recombinant protein expression.
DNA Extraction	This strain is EndA negative and thus yielding high quality DNA preparations.	XJb is not the best strain for DNA extraction. If necessary to do so, techniques should be chosen that yield highly purified DNA in the least amount of time.
DNA Stability	The RecA negative mutation in XJa stabilizes repetitive DNA sequences.	This strain is RecA positive.

STRAIN GENOTYPES
XJa Autolysis™	E. coli K recA1 supE44 endA1 hsdR17 (r_k^-,m_k⁺) gyrA96 relA1 thi mcrA (lac-proAB) araB::R, cat F’[traD36 proAB+ lacI^q lacZM15]
XJb Autolysis™	E. coli B F^- ompT hsdS_B(r_B^- m_B^-) gal dcm⁺ araB::R, cat