Difference between revisions of "Part:BBa K1088009"

Revision as of 18:48, 28 October 2013

B. subtilis dxs-GFP protein fusion (lac promoter with LVA-tagged lac inhibitor (LacI:LVA) - IPTG ind

This part consist of the dxs gene derived from B. subtilis fused to GFP at the translational level with a 10 AA linker between the proteins. The reporter fusion is under the control of the lac promoter and has a strong RBS.

To repress expression from the lac promoter, the lacI:LVA (gene under a constitutive promoter, with a strong RBS and an efficient terminator) was placed upstream to the reporter fusion. The repression can be relieved with addition of IPTG, which binds and inhibits the function of LacI:LVA.

This brick was build to assay the expression profile before and after induction of a similar device (BBa_K1088013) which lacks the linker and GFP.

Fluorescense activated cell sorting (FACS) was used to measure protein expression, and a similar device (BBa_K1088008) without the part that overexpresses lacI:LVA was used for comparison.

FACS results and growth curves of +/-lacI:LVA carrying strains. One triplicate of MG1655 (WT) and two triplicates of MG1655 strains carrying either BBa_K1088008(-lacI:LVA) or BBa_K1088009 (+lacI:LVA) were grown from OD₆₀₀ 0.005 to approximately 0.2. At this OD the MG1655 triplicate and one triplicate of each strain carrying constructs were induced with 1 mM IPTG at time 0 min. FACS measurements were done at times: -30, 0, 30, 60, 90, 120, and 150 min.

A) Growth curve shows that WT cells grow slightly faster than strains carrying plasmids. B) Percent of population above fluorescence threshold. None of the WT cells were fluorescent, almost all of the -lacI:LVA cells were constitutively fluorescent, and only cells overexpressing LacI:LVA weren’t fluorescent when not induced. Upon induction increasing percent of +lacI:LVA carrying cells became fluorescent and reached a maximum of 70-75 percent after 90 min. C) Mean GFP fluorescence of the entire population. The -lacI:LVA cells became increasingly more fluorescent over time, both with and without induction. The induced cells were slightly more fluorescent, which is probably because of the relief of repression from LacI naturally present in the cells. For the +lacI:LVA cells the results from B is reflected.

Sequence and Features