Regulated genetic suicide mechanism compositions and methods
Embodiments of the present invention relates to the incorporation and use of a regulated genetic suicide mechanism for use in the improved purification of biologics, including adjunct use in various eubacterial minicell production and purification methodologies. Described herein are high-yield eubacterial minicell-producing strains with genetic modifications that comprise a regulated genetic suicide mechanism that irreparably destroys the parent cell chromosome such that live parental cells in a culture can be functionally eliminated at any time during the course of a minicell production and purification run. Embodiments of the present invention also describe methods useful in the elimination of live parental cells during the production of other cell-based biologics.
1. A minicell-producing bacteria, comprising
an expressible cell division gene, wherein the cell division gene is ftsZ, sulA, ccdB, or sfiC; and
an expressible gene encoding a homing endonuclease, wherein the homing endonuclease gene is a transgene,
wherein the chromosome of the minicell-producing bacteria comprises one or more recognition sites of the endonuclease.
2. The minicell-producing bacteria of claim 1 , wherein the minicell-producing gene is a transgene.
3. The minicell-producing bacteria of claim 1 , wherein the cell division gene is ftsZ.
4. The minicell-producing bacteria of claim 1 , wherein the cell division gene is expressed under the control of an inducible promoter.
5. The minicell-producing bacteria of claim 4 , wherein the promoter is inducible by the presence of one or more chemical compounds.
6. The minicell-producing bacteria of claim 1 , wherein the endonuclease gene is located on the chromosome of the minicell-producing bacteria.
7. The minicell-producing bacteria of claim 1 , wherein the homing endonuclease is selected from the group consisting of I-CeuI, PI-Scel, I-ChuI, I-CpaI, I-SceIII, I-CreI, I-MsoI, I-SceII, I-SceIV, I-CsmI, I-DmoI, I-PorI, PI-TliI, PI-TliII, and PI-ScpI.
8. The minicell-producing bacteria of claim 7 , wherein the endonuclease is I-CeuI.
9. The minicell-producing bacteria of claim 1 , wherein the homing endonuclease is expressed under the control of an inducible promoter.
10. The minicell-producing bacteria of claim 9 , wherein the inducible promoter is a temperature-sensitive promoter.
11. The minicell-producing bacteria of claim 1 , wherein the minicell-producing bacteria is a Gram-negative bacteria.
12. The minicell-producing bacteria of claim 11 , wherein the Gram-negative bacteria is selected from the group consisting of Campylobacter jejuni, Lactobacillus spp., Neisseria gonorrhoeae, Legionella pneumophila, Salmonella spp., Shigella spp., Pseudomonas aeruginosa , and Escherichia coli.
13. The minicell-producing bacteria of claim 11 , comprising a gene encoding a gene product that is involved in lipopolysaccharide synthesis, wherein the gene is genetically modified compared to a corresponding wild-type gene.
14. The minicell-producing bacteria of claim 13 , wherein the gene is a msbB gene that encodes a gene product that causes the bacteria to produce an altered lipid A molecule compared to lipid A molecules in a corresponding wild-type bacteria.
15. The minicell-producing bacteria of claim 14 , wherein the altered lipid A molecule is deficient with respect to the addition of myristolic acid to the lipid A portion of the lipopolysaccharide molecule compared to lipid A molecules in a corresponding wild-type bacteria.